64 results on '"Davies AA"'
Search Results
2. Low-grade inflammatory markers: levels and determinants in a rural West African population
- Author
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Davies, AA, Moore, SE, Fulford, AJ, and Prentice, AM
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- 2007
3. Low birth weight is associated with higher adult total cholesterol concentration in men: findings from an occupational cohort of 25 843 employees.
- Author
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Davies AA, Smith GD, Ben-Shlomo Y, and Litchfield P
- Published
- 2004
4. Prediction of DXA-determined whole body fat from skinfolds: Importance of including skinfolds from the thigh and calf in young, healthy men and women
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S Charlesworth, Roger G. Eston, Ann V. Rowlands, T Hoppitt, A Davies, Rowlands, Alex Viktor, Eston, Roger George, Charlesworth, S, Davies, AA, and Hoppitt, T
- Subjects
Adult ,Male ,musculoskeletal diseases ,medicine.medical_specialty ,Cross-sectional study ,Medicine (miscellaneous) ,Thigh ,Models, Biological ,Fat mass ,Absorptiometry, Photon ,Predictive Value of Tests ,Reference Values ,Humans ,Medicine ,Leg ,Nutrition and Dietetics ,business.industry ,Reproducibility of Results ,nutritional and metabolic diseases ,Anatomy ,musculoskeletal system ,Skinfold Thickness ,Cross-Sectional Studies ,Skinfold thickness ,medicine.anatomical_structure ,Adipose Tissue ,Predictive value of tests ,Reference values ,Arm ,Body Composition ,Physical therapy ,Regression Analysis ,population characteristics ,Female ,Human Movement and Sports Science ,business ,Whole body ,human activities ,Body mass index - Abstract
To investigate the relationship of percent body fat (%fat), assessed by dual energy-X-ray absorptiometry (DXA) or a four-compartment model, with upper body and lower limb skinfolds.Cross-sectional design involving forward stepwise and hierarchical multiple regression analyses to assess the relationship of %fat with skinfolds and a combination of four commonly used upper body skinfolds (biceps, triceps, subscapular and iliac crest) with the calf and thigh skinfolds.University research laboratory.In all, 31 females, mean age 20.9 (+/-2.0) y, and 21 males, mean age 22.3 (+/-5.5) y volunteered for this study, which was approved by the Ethics Committee of the School of Sport, Health and Exercise Sciences, University of Wales, Bangor.%fat from DXA in both groups, and %fat from a four-compartment (water, bone mineral mass, fat and residual) model (%fat4C) in females only. Skinfolds were measured at the abdomen, iliac crest, biceps, triceps, subscapular, calf and thigh.All skinfolds were positively associated with DXA estimates of %fat (P0.01). In males and females, the thigh skinfold had the highest correlation with %fat. This was also observed when %fat4C was used as the criterion in females. Stepwise multiple regression analysis using %fatDXA as the criterion selected the thigh (R(2) = 0.82), calf (R(2) change 0.04) and iliac crest (R(2) change = 0.03) for females, and the thigh (R(2) = 0.79), iliac crest (R(2) change = 0.11) and abdomen (R(2) change = 0.03) for males (all P0.01). When %fat4C was used as the criterion in the females, only the thigh was selected as a significant predictor (R(2) = 0.76). Independent prediction factors were created from the sum of biceps, triceps, subscapular and iliac crest (sigma4skf) and from the sum of the thigh and calf (sigmathigh + calf). These factors were then entered into a hierarchical multiple linear regression analysis to predict percent fat. Order of entry was varied to allow the assessment of unique variance accounted for by each predictor. The sum of the thigh and calf explained more variance in %fatDXA than that explained by the sigma4skf alone, irrespective of the order of entry in both males and females. This was also observed when %fat4C was used as the criterion in the females.The results of this study confirm that lower body skinfolds are highly related to percent body fat in fit and healthy young men and women, and uphold current recommendations by the British Olympic Association to include the thigh skinfold with sigma4skf. Conventional use of the sigma4skf to estimate percent body fat is significantly enhanced by the inclusion of the thigh and calf skinfolds, either independently or in combination. In this group of males and females, the sum of the thigh and calf skinfolds accounted for the most variance in percent fat.
- Published
- 2005
5. Prevalence of Chronic Pulmonary Aspergillosis in Two (2) Tuberculosis Treatment Clinics in Lagos, Nigeria: A Prospective Longitudinal Study.
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Davies AA, Adekoya AO, Balogun OJ, Osaigbovo II, Nwosu A, Gbaja-Biamila T, Osinupebi O, Gangneux JP, and Oladele RO
- Abstract
Background: Chronic pulmonary aspergillosis (CPA) is an underrecognized but common complication of pulmonary tuberculosis. In Nigeria, a tuberculosis-endemic country, there is currently no provision to monitor the development of CPA in patients treated for tuberculosis. This study determined the prevalence and incidence of CPA in Lagos, Nigeria., Methods: A prospective longitudinal study of patients with previously managed tuberculosis was conducted between June 2021 and May 2022. The study cohorts were assessed at 3-month intervals, and the following were collected: sociodemographic data, chest radiographic findings, sputum samples for fungal culture, and venous blood samples for Aspergillus immunoglobulin G estimation. CPA cases were determined using the case definition for resource-constrained countries. Descriptive and inferential statistics were used, and significance was set at a probability of 5% ( P < .05)., Results: Of the 141 patients recruited, 79 (56.0%) were in the retreatment and 62 (44.0%) in the posttreatment tuberculosis group. The median age (interquartile range) was 40 (30-52) years, with a male-to-female ratio of 1.1:1. Ninety-seven patients (69%) had a GeneXpert test done, of whom 63 (64.9%) were GeneXpert negative. Cough was the most common symptom, with 15 (11%) patients having hemoptysis. The rate of CPA increased steadily as the study progressed: 44 (31.2%) at commencement, 45 (34.9%) at 3 months, 49 (42.6%) at 6 months, and 51 (54.3%) at 9 months. Thus, the overall prevalence of CPA was 49.7%, and the incidence was 6.1%., Conclusions: CPA is common in Nigeria and its true burden may still be underestimated. Increased awareness of CPA as a posttuberculosis lung disease is advocated. Evaluation for CPA should be incorporated in patients' work-up for tuberculosis., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)
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- 2024
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6. Candida auris : A Systematic Review of a Globally Emerging Fungal Pathogen in Africa.
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Osaigbovo II, Ekeng BE, Davies AA, Ebeigbe E, Bongomin F, Kanyua A, Revathi G, and Oladele RO
- Abstract
Candida auris is a World Health Organization critical priority fungal pathogen. We conducted a systematic review to describe its epidemiology in Africa. PubMed and Google scholar databases were searched between January 2009 and September 2023 for clinical studies on C. auris cases and/or isolates from Africa. Reviews were excluded. We included 19 studies, involving at least 2529 cases from 6 African countries with the most, 2372 (93.8%), reported from South Africa. Whole-genome sequencing of 127 isolates identified 100 (78.7%) as clade III. Among 527 isolates, 481 (91.3%) were resistant to fluconazole, 108 (20.5%) to amphotericin B, and 9 (1.7%) to micafungin. Ninety of 211 (42.7%) patients with clinical outcomes died. C. auris is associated with high mortality and antifungal resistance, yet this critical pathogen remains underreported in Africa. Collaborative surveillance, fungal diagnostics, antifungals, and sustainable infection control practices are urgently needed for containment., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts,, (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)
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- 2023
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7. Mucormycosis in Africa: Epidemiology, diagnosis and treatment outcomes.
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Osaigbovo II, Ekeng BE, Davies AA, and Oladele RO
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- Humans, Treatment Outcome, Africa, Rhizopus oryzae, Antifungal Agents therapeutic use, COVID-19 Testing, Mucormycosis diagnosis, Mucormycosis drug therapy, Mucormycosis epidemiology, COVID-19, Mucorales
- Abstract
Mucorales fungi cause mucormycosis, an invasive and rapidly progressive disease which increasingly affects mostly immunocompromised but also immunocompetent individuals. The objective of this study was to highlight the epidemiology, diagnostic modalities, treatment and overall survival of mucormycosis in Africa. We searched for relevant publications in PubMed, Google Scholar and African Journal Online databases covering the period 1960-2022. A total of 147 articles were identified, of which 66 were included in the review, detailing 408 individual cases from 12 African countries; 330 (80.9%) from North Africa, 63 (15.4%) from Southern Africa, seven (1.7%) from East Africa, seven (1.7%) from West Africa and a single case (0.2%) from Central Africa. The most frequently described clinical forms were rhino-orbital-cerebral (n = 307, 75.2%) and gastrointestinal (n = 51, 12.5%). Diabetes mellitus, COVID-19, malignancies and neutropaenia were the commonest underlying risks in 203 (49.8%), 101 (24.8%), 65 (15.9%) and 53 (13.0%) cases respectively. Most cases, 296 (72.5%) were diagnosed by histopathology. Fungal aetiology was identified in 38 (9.3%), of which the commonest was Rhizopus oryzae/arrhizus (27/38, 71.1%). Of the 408 cases, 334 (81.9%) patients received antifungal therapy, while 244 (59.8%) had surgery. In cases with a specified outcome, survival rate was 59.1% (228/386). Based on case reporting, a substantial burden of mucormycosis occurs in North Africa but the disease is rarely reported in most of the sub-Saharan region. Establishing a comprehensive registry for standardised data collection could improve understanding of the epidemiology of mucormycosis in the region., (© 2023 Wiley-VCH GmbH.)
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- 2023
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8. A multicenter survey of asymptomatic cryptococcal antigenemia among patients with advanced HIV disease in Nigeria.
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Oladele RO, Jordan AM, Okaa JU, Osaigbovo II, Shettima SA, Shehu NY, Davies AA, Mohammed Y, Alex-Wele MA, Iliyasu G, Nwaokenye JC, Fayemiwo SA, Udoh UA, Gbajabiamila T, Denning DW, and Chiller TM
- Abstract
As of 2018, cryptococcal antigen (CrAg) screening in patients with advanced human immunodeficiency virus (HIV) disease (AHD) was not routinely implemented in Nigeria despite being recommended in the national HIV treatment guidelines. Our aim was to determine the prevalence and risk factors for asymptomatic cryptococcal antigenemia in adult people living with HIV (PLHIV) in Nigeria to advocate for the implementation of routine CrAg screening. A descriptive cross-sectional study and CrAg screening of consecutive adult PLHIV with CD4 counts ≤200 cells/μL was conducted from April 2018 to April 2019 at HIV clinics in eleven tertiary hospitals spread across Nigeria's six geopolitical regions. Prevalence of asymptomatic cryptococcal antigenemia was estimated by facility and geopolitical zone. Logistic regression was conducted to identify risk factors for cryptococcal antigenemia. In total, 1,114 patients with AHD were screened. The overall prevalence of asymptomatic cryptococcal antigenemia was 3.9% with wide variation across facilities (range: 0/75 [0%]- 15/122 [12.3%]) and geopolitical zones (range: 0/75 [0%]-19/279 [6.8%]). Prevalence of antigenemia was highest in the South-West (19/279 [6.8%]) and lowest in the North-East (0/75 [0%]). Prevalence was 5.2% (26/512) and 3.2% (18/561) in patients with CD4<100 and CD4 of 101-200, respectively. Of all patients with antigenemia, 50% were on antiretroviral therapy (ART) at the time of having a positive CrAg test. In adjusted analysis, cryptococcal antigenemia was significantly less in patients on ART and patients who had completed any formal education. The survey showed a high overall burden of cryptococcal antigenemia in Nigeria, with variable prevalence across geopolitical regions. We provided valuable evidence for implementing routine CrAg screening of AHD patients in Nigeria which has commenced in selected centres., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: DWD and family hold Founder shares in F2G Ltd, a University of Manchester spin-out antifungal discovery company, and share options in TFF Pharma. He acts or has recently acted as a consultant to Pulmatrix, Pulmocide, Biosergen, TFF Pharmaceuticals, Bright Angel Therapeutics and Cipla. He sits on the DSMB for a SARS CoV2 vaccine trial. In the last 3 years, he has been paid for talks on behalf of Hikma, Gilead, BioRad, Basilea, Mylan and Pfizer. DWD did not receive a salary from any of the commercial affiliations during the time of the study. Additionally, all commercial funding author DWD received were unrelated to, and outside of, the submitted work. All other authors declare that they have no financial or personal relationship(s) that may have inappropriately influenced them in writing this article. There are no patents, products in development or marketed products associated with this research to declare. The competing interests listed do not alter our adherence to PLOS ONE policies on sharing data and materials., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)
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- 2023
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9. Current epidemiology of histoplasmosis in Nigeria: A systematic review and meta-analysis.
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Ekeng BE, Davies AA, Osaigbovo II, Emanghe UE, Udoh UA, Alex-Wele MA, Adereti OC, and Oladele RO
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- Humans, Nigeria, Histoplasma, Risk Factors, Histoplasmosis diagnosis, Histoplasmosis epidemiology, HIV Infections
- Abstract
Introduction: Histoplasmosis commonly occurs in the advanced HIV disease population and also in immunocompetent individuals. Previous reviews and recent studies highlight several cases of histoplasmosis reported in Nigeria. We aimed to describe the current epidemiology of histoplasmosis in Nigeria and the need for active surveillance in the at-risk populations., Methods: Literature searches for all publications on histoplasmosis in Nigeria were performed using online databases including Google scholar, PubMed and African Journal online. The following search terms: 'histoplasmosis' and 'Nigeria', AND/OR 'Histoplasma and Nigeria' were used. No limitations on the date or other search criteria were applied, to avoid the exclusion of articles on histoplasmosis in Nigeria. All publications on histoplasmosis outside Nigeria were excluded., Results: Our review identified a total of 231 cases of histoplasmosis reported from Nigeria: 128 were from individual case reports and case series while 103 were cases from two observational studies. Of the 231 cases, 97 (42.0%) were from South West Nigeria, 66 (28.6%) were from South-South Nigeria, 24 (10.4%) were from North West, 22 (9.5%) from North Central Nigeria, 17 (7.4%) from South East Nigeria and 5 (2.2%) from the North East. Based on Nigeria's current population size of 216,953,585 the burden of histoplasmosis per 100,000 inhabitants was estimated to be 0.1%. The sheer number of cases detected in recent observational studies compared with individual case reports and series reported over a longer duration of 6 decades suggests gross under-reporting of histoplasmosis in Nigeria., Conclusion: Histoplasmosis is not an uncommon clinical entity in Nigeria. Histoplasmosis case finding should be improved by training and retraining healthcare professionals and providing much-needed diagnostic capacity and infrastructure across health facilities in Nigeria., Competing Interests: None
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- 2023
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10. Invasive Fungal Diseases in Africa: A Critical Literature Review.
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Bongomin F, Ekeng BE, Kibone W, Nsenga L, Olum R, Itam-Eyo A, Kuate MPN, Pebolo FP, Davies AA, Manga M, Ocansey B, Kwizera R, and Baluku JB
- Abstract
Invasive fungal diseases (IFDs) are of huge concern in resource-limited settings, particularly in Africa, due to the unavailability of diagnostic armamentarium for IFDs, thus making definitive diagnosis challenging. IFDs have non-specific systemic manifestations overlapping with more frequent illnesses, such as tuberculosis, HIV, and HIV-related opportunistic infections and malignancies. Consequently, IFDs are often undiagnosed or misdiagnosed. We critically reviewed the available literature on IFDs in Africa to provide a better understanding of their epidemiology, disease burden to guide future research and interventions. Cryptococcosis is the most encountered IFD in Africa, accounting for most of the HIV-related deaths in sub-Saharan Africa. Invasive aspergillosis, though somewhat underdiagnosed and/or misdiagnosed as tuberculosis, is increasingly being reported with a similar predilection towards people living with HIV. More cases of histoplasmosis are also being reported with recent epidemiological studies, particularly from Western Africa, showing high prevalence rates amongst presumptive tuberculosis patients and patients living with HIV. The burden of pneumocystis pneumonia has reduced significantly probably due to increased uptake of anti-retroviral therapy among people living with HIV both in Africa, and globally. Mucormycosis, talaromycosis, emergomycosis, blastomycosis, and coccidiomycosis have also been reported but with very few studies from the literature. The emergence of resistance to most of the available antifungal drugs in Africa is yet of huge concern as reported in other regions. IFDs in Africa is much more common than it appears and contributes significantly to morbidity and mortality. Huge investment is needed to drive awareness and fungi related research especially in diagnostics and antifungal therapy.
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- 2022
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11. Chronic cavitary pulmonary aspergillosis in an immunocompetent child.
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Davies AA, Adegbite IA, Akintan PE, Ibrahim UO, Adekoya AO, and Oladele RO
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Chronic pulmonary aspergillosis (CPA) is a progressive and destructive disease of the lung parenchyma. We report a 9-year-old boy diagnosed with CPA with a positive Aspergillus IgG and chest imaging of cavitary lung lesions. He was treated with oral Itraconazole with significant improvement. This shows that an index of suspicion should be heightened in the paediatric population with cavitary lung lesions because not all cavitary lung lesions are caused by Mycobacterium tuberculosis., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors.)
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- 2022
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12. Pulmonary and Extrapulmonary Manifestations of Fungal Infections Misdiagnosed as Tuberculosis: The Need for Prompt Diagnosis and Management.
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Ekeng BE, Davies AA, Osaigbovo II, Warris A, Oladele RO, and Denning DW
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Fungal infections commonly present with myriad symptoms that mimic other clinical entities, notable amongst which is tuberculosis. Besides histoplasmosis and chronic pulmonary aspergillosis, which can mimic TB, this review has identified several other fungal infections which also do. A total of 80 individual cases misdiagnosed as TB are highlighted: aspergillosis ( n = 18, 22.5%), histoplasmosis ( n = 16, 20%), blastomycosis ( n = 14, 17.5%), cryptococcosis ( n = 11, 13.8%), talaromycosis ( n = 7, 8.8%), coccidioidomycosis ( n = 5, 6.3%), mucormycosis ( n = 4, 5%), sporotrichosis ( n = 3, 3.8%), phaeohyphomycosis ( n = 1, 1.3%) and chromoblastomycosis ( n = 1, 1.3%). Case series from India and Pakistan reported over 100 cases of chronic and allergic bronchopulmonary aspergillosis had received anti-TB therapy before the correct diagnosis was made. Forty-five cases (56.3%) had favorable outcomes, and 25 (33.8%) died, outcome was unclear in the remainder. Seventeen (21.3%) cases were infected with human immunodeficiency virus (HIV). Diagnostic modalities were histopathology ( n = 46, 57.5%), culture ( n = 42, 52.5%), serology ( n = 18, 22.5%), cytology ( n = 2, 2.5%), gene sequencing ( n = 5, 6.3%) and microscopy ( n = 10, 12.5%) including Gram stain, India ink preparation, bone marrow smear and KOH mount. We conclude that the above fungal infections should always be considered or ruled out whenever a patient presents with symptoms suggestive of tuberculosis which is unconfirmed thereby reducing prolonged hospital stay and mortalities associated with a delayed or incorrect diagnosis of fungal infections.
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- 2022
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13. An Economical and Versatile High-Throughput Protein Purification System Using a Multi-Column Plate Adapter.
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Kineavy FB, Davies AA, Mitchell MR, Lay D, Dominguez MJ, and Stollar EJ
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- Chromatography, Affinity methods, Vacuum, Proteins isolation & purification, Proteomics methods
- Abstract
Protein purification is imperative to the study of protein structure and function and is usually used in combination with biophysical techniques. It is also a key component in the development of new therapeutics. The evolving era of functional proteomics is fueling the demand for high-throughput protein purification and improved techniques to facilitate this. It was hypothesized that a multi column plate adaptor (MCPA) can interface multiple chromatography columns of different resins with multi-well plates for parallel purification. This method offers an economical and versatile method of protein purification that can be used under gravity or vacuum, rivaling the speed of an automated system. The MCPA can be used to recover milligram yields of protein by an affordable and time efficient method for subsequent characterization and analysis. The MCPA has been used for high-throughput affinity purification of SH3 domains. Ion exchange has also been demonstrated via the MCPA to purify protein post Ni-NTA affinity chromatography, indicating how this system can be adapted to other purification types. Due to its setup with multiple columns, individual customization of parameters can be made in the same purification, unachievable by the current plate-based methods.
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- 2021
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14. Importance of the inverted control in measuring holistic face processing with the composite effect and part-whole effect.
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McKone E, Davies AA, Darke H, Crookes K, Wickramariyaratne T, Zappia S, Fiorentini C, Favelle S, Broughton M, and Fernando D
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Holistic coding for faces is shown in several illusions that demonstrate integration of the percept across the entire face. The illusions occur upright but, crucially, not inverted. Converting the illusions into experimental tasks that measure their strength - and thus index degree of holistic coding - is often considered straightforward yet in fact relies on a hidden assumption, namely that there is no contribution to the experimental measure from secondary cognitive factors. For the composite effect, a relevant secondary factor is size of the "spotlight" of visuospatial attention. The composite task assumes this spotlight can be easily restricted to the target half (e.g., top-half) of the compound face stimulus. Yet, if this assumption were not true then a large spotlight, in the absence of holistic perception, could produce a false composite effect, present even for inverted faces and contributing partially to the score for upright faces. We review evidence that various factors can influence spotlight size: race/culture (Asians often prefer a more global distribution of attention than Caucasians); sex (females can be more global); appearance of the join or gap between face halves; and location of the eyes, which typically attract attention. Results from five experiments then show inverted faces can sometimes produce large false composite effects, and imply that whether this happens or not depends on complex interactions between causal factors. We also report, for both identity and expression, that only top-half face targets (containing eyes) produce valid composite measures. A sixth experiment demonstrates an example of a false inverted part-whole effect, where encoding-specificity is the secondary cognitive factor. We conclude the inverted face control should be tested in all composite and part-whole studies, and an effect for upright faces should be interpreted as a pure measure of holistic processing only when the experimental design produces no effect inverted.
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- 2013
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15. Detection of PCNA modifications in Saccharomyces cerevisiae.
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Davies AA and Ulrich HD
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- Blotting, Western, Chromatography, Affinity, DNA Damage, Electrophoresis, Polyacrylamide Gel, Nitrilotriacetic Acid analogs & derivatives, Nitrilotriacetic Acid chemistry, Organometallic Compounds chemistry, Proliferating Cell Nuclear Antigen isolation & purification, SUMO-1 Protein, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae Proteins isolation & purification, Ubiquitination, Proliferating Cell Nuclear Antigen metabolism, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins metabolism
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PCNA modifications by members of the ubiquitin family are associated with a range of different transactions during replication of damaged and undamaged DNA. This chapter describes detailed protocols for the detection and isolation of ubiquitin and SUMO conjugates of PCNA from total budding yeast cell lysates, using Ni-NTA affinity chromatography under denaturing conditions. We describe approaches based on the purification of PCNA itself and on the isolation of total ubiquitin or SUMO conjugates. The chapter covers the construction of the appropriate strains, methods for the detection of modified PCNA, and the use of various DNA-damaging agents as well as mutants of PCNA and relevant conjugation enzymes to examine the cellular response to replication stress.
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- 2012
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16. The dynamics of health and return migration.
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Davies AA, Borland RM, Blake C, and West HE
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- Community Health Services organization & administration, Delivery of Health Care legislation & jurisprudence, Delivery of Health Care organization & administration, Humans, Public Health, Risk Factors, Socioeconomic Factors, Emigration and Immigration, Health Policy legislation & jurisprudence, Health Services Accessibility
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The increasing importance and complexity of migration globally also implies a global increase in return migration, and thus an increased interest in the health of returning migrants. The health of returning migrants is impacted by the cumulative exposure to social determinants and risk factors of health during the migration process, during the return movement, and following return. Circular migration often occurs among the diaspora, which can result in the transfer of knowledge and skills that contribute to development, including health system strengthening. Migrants with dual nationality often return to countries with better health services than their country of origin when they are sick and can not get care at home. To maintain and improve the health of returning migrants, multi-sectoral policies at global and national levels should facilitate access to appropriate and equitable health services, social services, and continuity of care across and within borders.
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- 2011
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17. Ubiquitin-dependent DNA damage bypass is separable from genome replication.
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Daigaku Y, Davies AA, and Ulrich HD
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- Cell Cycle physiology, Chromatin metabolism, DNA Damage radiation effects, Proliferating Cell Nuclear Antigen metabolism, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins, Time Factors, Ubiquitin-Conjugating Enzymes, Ultraviolet Rays, DNA Damage genetics, DNA Replication genetics, Genome genetics, Saccharomyces cerevisiae cytology, Saccharomyces cerevisiae genetics, Ubiquitin metabolism
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Post-replication repair (PRR) is a pathway that allows cells to bypass or overcome lesions during DNA replication. In eukaryotes, damage bypass is activated by ubiquitylation of the replication clamp PCNA through components of the RAD6 pathway. Whereas monoubiquitylation of PCNA allows mutagenic translesion synthesis by damage-tolerant DNA polymerases, polyubiquitylation is required for an error-free pathway that probably involves a template switch to the undamaged sister chromatid. Both the timing of PRR events during the cell cycle and their location relative to replication forks, as well as the factors required downstream of PCNA ubiquitylation, have remained poorly characterized. Here we demonstrate that the RAD6 pathway normally operates during S phase. However, using an inducible system of DNA damage bypass in budding yeast (Saccharomyces cerevisiae), we show that the process is separable in time and space from genome replication, thus allowing direct visualization and quantification of productive PRR tracts. We found that both during and after S phase ultraviolet-radiation-induced lesions are bypassed predominantly via translesion synthesis, whereas the error-free pathway functions as a backup system. Our approach has revealed the distribution of PRR tracts in a synchronized cell population. It will allow an in-depth mechanistic analysis of how cells manage the processing of lesions to their genomes during and after replication.
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- 2010
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18. Ubiquitylation of the 9-1-1 checkpoint clamp is independent of rad6-rad18 and DNA damage.
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Davies AA, Neiss A, and Ulrich HD
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- Amino Acid Sequence, Humans, Molecular Sequence Data, Proteasome Endopeptidase Complex metabolism, Sequence Alignment, Ubiquitination, Cell Cycle Proteins metabolism, DNA Damage, DNA-Binding Proteins metabolism, Nuclear Proteins metabolism, Saccharomyces cerevisiae Proteins metabolism, Ubiquitin-Conjugating Enzymes metabolism
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A recent report proposed a function of the ubiquitin conjugation factors Rad6 and Rad18 comparable to the bacterial SOS response, controlling damage-induced transcriptional activation and contributing to checkpoint signaling. The relevant ubiquitylation target was identified as budding yeast Rad17, a subunit of the PCNA-like 9-1-1 checkpoint clamp. We report here that in fact all three subunits of the 9-1-1 complex are ubiquitylated. However, in contrast to previous results, we found modification of Rad17 to be independent of DNA damage, the Rad6-Rad18 complex, the putative acceptor site (lysine 197), and loading of the complex onto DNA. Consistently, we were unable to observe enhanced damage sensitivity or defects in checkpoint signaling in a rad17(K197R) mutant. Instead, our findings suggest that ubiquitylation of the 9-1-1 complex may be a background reaction that in some cases can mediate proteasomal degradation., (Copyright 2010 Elsevier Inc. All rights reserved.)
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- 2010
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19. Migration and health service delivery.
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Davies AA, Mosca D, and Frattini C
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- Health Personnel, Humans, Delivery of Health Care, Transients and Migrants
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Migration has positive and integrative effects on health service delivery. This paper presents initiatives promoting circular migration of diaspora health professionals to contribute to health service delivery and capacity development in their countries of origin. The paper will also highlight the contributions that foreign trained and foreign born health professionals can make to the delivery of migrant friendly health services for diverse multi-cultural populations.
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- 2010
20. In vivo detection and characterization of sumoylation targets in Saccharomyces cerevisiae.
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Ulrich HD and Davies AA
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- Clinical Laboratory Techniques, Cloning, Molecular methods, Models, Biological, Organisms, Genetically Modified, Saccharomyces cerevisiae chemistry, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae Proteins chemistry, Saccharomyces cerevisiae Proteins genetics, Saccharomyces cerevisiae Proteins metabolism, Small Ubiquitin-Related Modifier Proteins isolation & purification, Protein Processing, Post-Translational, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins isolation & purification, Small Ubiquitin-Related Modifier Proteins metabolism
- Abstract
Ni-NTA affinity chromatography under denaturing conditions has proven to be a powerful method for the isolation of SUMO conjugates from total cell extracts, as it minimizes deconjugation and excludes noncovalent interactions. This chapter describes the use of both His-tagged SUMO and a His-tagged target protein for the characterization of the sumoylation process in the budding yeast Saccharomyces cerevisiae. Two well-studied model substrates, the septin Cdc3 and the replication clamp protein PCNA, are used as examples, but the protocol can easily be adapted to other targets and organisms.
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- 2009
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21. SUMO modification of PCNA is controlled by DNA.
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Parker JL, Bucceri A, Davies AA, Heidrich K, Windecker H, and Ulrich HD
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- Alleles, Chromatin metabolism, Cysteine Endopeptidases chemistry, DNA chemistry, Models, Biological, Models, Genetic, Protein Binding, Protein Processing, Post-Translational, Protein Structure, Tertiary, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins chemistry, Ubiquitin chemistry, Ubiquitin-Protein Ligases chemistry, Gene Expression Regulation, Fungal, Proliferating Cell Nuclear Antigen metabolism, SUMO-1 Protein metabolism
- Abstract
Post-translational modification by the ubiquitin-like protein SUMO is often regulated by cellular signals that restrict the modification to appropriate situations. Nevertheless, many SUMO-specific ligases do not exhibit much target specificity, and--compared with the diversity of sumoylation substrates--their number is limited. This raises the question of how SUMO conjugation is controlled in vivo. We report here an unexpected mechanism by which sumoylation of the replication clamp protein, PCNA, from budding yeast is effectively coupled to S phase. We find that loading of PCNA onto DNA is a prerequisite for sumoylation in vivo and greatly stimulates modification in vitro. To our surprise, however, DNA binding by the ligase Siz1, responsible for PCNA sumoylation, is not strictly required. Instead, the stimulatory effect of DNA on conjugation is mainly attributable to DNA binding of PCNA itself. These findings imply a change in the properties of PCNA upon loading that enhances its capacity to be sumoylated.
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- 2008
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22. Activation of ubiquitin-dependent DNA damage bypass is mediated by replication protein a.
- Author
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Davies AA, Huttner D, Daigaku Y, Chen S, and Ulrich HD
- Subjects
- Animals, Cell Cycle physiology, Cell Line, DNA Replication, DNA, Single-Stranded genetics, DNA-Binding Proteins genetics, DNA-Binding Proteins metabolism, Humans, Proliferating Cell Nuclear Antigen genetics, Proliferating Cell Nuclear Antigen metabolism, Replication Protein A genetics, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins genetics, Saccharomyces cerevisiae Proteins metabolism, Two-Hybrid System Techniques, Ubiquitin genetics, DNA Damage, DNA, Single-Stranded metabolism, Replication Protein A metabolism, Ubiquitin metabolism
- Abstract
Replicative DNA damage bypass, mediated by the ubiquitylation of the sliding clamp protein PCNA, facilitates the survival of a cell in the presence of genotoxic agents, but it can also promote genomic instability by damage-induced mutagenesis. We show here that PCNA ubiquitylation in budding yeast is activated independently of the replication-dependent S phase checkpoint but by similar conditions involving the accumulation of single-stranded DNA at stalled replication intermediates. The ssDNA-binding replication protein A (RPA), an essential complex involved in most DNA transactions, is required for damage-induced PCNA ubiquitylation. We found that RPA directly interacts with the ubiquitin ligase responsible for the modification of PCNA, Rad18, both in yeast and in mammalian cells. Association of the ligase with chromatin is detected where RPA is most abundant, and purified RPA can recruit Rad18 to ssDNA in vitro. Our results therefore implicate the RPA complex in the activation of DNA damage tolerance.
- Published
- 2008
- Full Text
- View/download PDF
23. Ethnic differences in the association between body mass index and impedance index (Ht2/Z) in adult women and men using a leg-to-leg bioimpedance method.
- Author
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Siervo M, Davies AA, Jebb SA, Jalil F, Moore SE, and Prentice AM
- Subjects
- Adolescent, Adult, Asian People, Black People, Body Height physiology, Body Weight physiology, Extremities physiology, Female, Humans, Male, Middle Aged, Reproducibility of Results, Sensitivity and Specificity, White People, Body Composition physiology, Body Mass Index, Electric Impedance, Ethnicity
- Abstract
Background: Ethnic differences in the association between body mass index (BMI) and body fat suggest that body composition varies across ethnic groups., Objective: To investigate the association between impedance index - a measure of tissue resistivity - and BMI in adults of different ethnic groups (Asian Indians, West Africans and White Caucasians) living in their native countries., Methods: Male (n=329) and female (n=277) adult subjects (18-50 years) living in urban areas in the UK, The Gambia and Pakistan were studied. Body weight and height were measured and BMI calculated. The same leg-to-leg bioimpedance instrument was used in each study and impedance index (height(2) (cm)/impedance (Omega)) used as measure of tissue resistivity., Results: In women, Asian Indians and West Africans had a significantly greater increase in impedance index per unit increase in BMI compared with white Caucasians (P<0.001). In men, Asian Indians had a significantly lower impedance index compared with West Africans and white Caucasians (P<0.001)., Conclusion: Different ethnic groups may have different tissue resistivity for the same BMI indicative of systematic differences in body composition.
- Published
- 2007
- Full Text
- View/download PDF
24. Complex I binding by a virally encoded RNA regulates mitochondria-induced cell death.
- Author
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Reeves MB, Davies AA, McSharry BP, Wilkinson GW, and Sinclair JH
- Subjects
- Adenosine Triphosphate metabolism, Apoptosis Regulatory Proteins genetics, Apoptosis Regulatory Proteins metabolism, Cell Line, Cell Line, Tumor, Cell Nucleus metabolism, Cytomegalovirus genetics, Cytomegalovirus growth & development, Electron Transport Complex I antagonists & inhibitors, Enzyme Inhibitors pharmacology, Fibroblasts metabolism, Fibroblasts virology, Humans, Membrane Potential, Mitochondrial, NADH, NADPH Oxidoreductases genetics, NADH, NADPH Oxidoreductases metabolism, Oxidative Stress, RNA, Untranslated genetics, RNA, Untranslated metabolism, RNA, Viral genetics, Rotenone pharmacology, Apoptosis, Cytomegalovirus physiology, Electron Transport Complex I metabolism, Mitochondria metabolism, Neurons cytology, Neurons virology, RNA, Viral metabolism
- Abstract
Human cytomegalovirus infection perturbs multiple cellular processes that could promote the release of proapoptotic stimuli. Consequently, it encodes mechanisms to prevent cell death during infection. Using rotenone, a potent inhibitor of the mitochondrial enzyme complex I (reduced nicotinamide adenine dinucleotide-ubiquinone oxido-reductase), we found that human cytomegalovirus infection protected cells from rotenone-induced apoptosis, a protection mediated by a 2.7-kilobase virally encoded RNA (beta2.7). During infection, beta2.7 RNA interacted with complex I and prevented the relocalization of the essential subunit genes associated with retinoid/interferon-induced mortality-19, in response to apoptotic stimuli. This interaction, which is important for stabilizing the mitochondrial membrane potential, resulted in continued adenosine triphosphate production, which is critical for the successful completion of the virus' life cycle. Complex I targeting by a viral RNA represents a refined strategy to modulate the metabolic viability of the infected host cell.
- Published
- 2007
- Full Text
- View/download PDF
25. Association between birth weight and blood pressure is robust, amplifies with age, and may be underestimated.
- Author
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Davies AA, Smith GD, May MT, and Ben-Shlomo Y
- Subjects
- Adult, Blood Pressure Determination standards, Cohort Studies, Female, Humans, Linear Models, Male, Aging physiology, Birth Weight, Blood Pressure
- Abstract
Data on the early life origins of adult hypertension have been widely reported: however, recent research shows that the strength of association between small size at birth and higher blood pressure weakens as study size increases. In this article, we retest the association between birth weight and systolic blood pressure in a large cohort, examine whether age interacts with birth weight to predict blood pressure, and explore reasons why birth weight-blood pressure associations tend to weaken with increasing study size. Measurements from 25874 employees of a large United Kingdom company (mean [SD] age: 38.0 [7.9] years), undertaking voluntary occupational health screening, were available. Using linear regression analysis, we observed that systolic blood pressure changed -0.8 (95% CI: -1.1 to -0.5) mmHg per 1-kg increase in birth weight (P<0.001) adjusted for age and sex and -1.1 (95% CI: -1.3 to -0.8) mmHg/kg (P<0.001) after further adjustment for body size. This inverse association amplified with age (age/birth weight interaction term P<0.001). In participants reporting birth weight from hospital records (n=744), systolic blood pressure changed -1.4 (95% CI: -3.1 to 0.2) mmHg/kg compared with -0.8 (95% CI: -1.0 to -0.5) mmHg/kg in all of the other participants. Finally, the data show evidence of "fixed-category blood pressure allocation," where participants are allocated certain blood pressure values, such as 120/80 mmHg, independent of actual blood pressure. Although the association between birth weight and systolic blood pressure was weaker than observed in smaller studies, recalled birth weight and fixed blood pressure measurement error may generate a trend toward weaker associations in larger studies.
- Published
- 2006
- Full Text
- View/download PDF
26. Nutritional interventions and outcome in patients with cancer or preinvasive lesions: systematic review.
- Author
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Davies AA, Davey Smith G, Harbord R, Bekkering GE, Sterne JA, Beynon R, and Thomas S
- Subjects
- Antioxidants administration & dosage, Complementary Therapies, Controlled Clinical Trials as Topic, Disease Progression, Disease-Free Survival, Double-Blind Method, Humans, Neoplasm Recurrence, Local epidemiology, Neoplasms diet therapy, Neoplasms mortality, Neoplasms, Second Primary epidemiology, Odds Ratio, Precancerous Conditions diet therapy, Precancerous Conditions mortality, Prognosis, Research Design, Single-Blind Method, Weight Loss, Dietary Supplements, Feeding Behavior, Neoplasms therapy, Precancerous Conditions therapy, Vitamins administration & dosage
- Abstract
Background: Dietary modifications and supplements are used widely by patients with cancer and preinvasive lesions as an adjunct to standard treatment. Given the widespread use of nutritional modifications and supplements by such patients and concerns about the lack of benefit and possible harm, we conducted a systematic review of randomized controlled trials to examine the effect of nutritional interventions on patients with cancer or preinvasive lesions., Methods: We searched electronic databases and reference lists to locate all eligible trials and analyzed trial quality. Outcome measures were all-cause and cancer mortality, disease-free survival, cancer recurrence, second primary cancer, recurrence of a preinvasive lesion, or progression to cancer. Results of individual trials were combined by use of random-effects meta-analyses., Results: We identified 59 eligible trials, 25 in patients with cancer and 34 in patients with preinvasive lesions, respectively. Trial quality was generally low; only three trials (two of cancer and one of preinvasive lesions) had adequate methods for generating the allocation sequence, allocation concealment, and masking both outcome assessors and participants. The combined odds ratio (OR) for the effect of a healthy diet-given alone or with dietary supplements, weight loss, or exercise-on all-cause mortality was 0.90 (95% confidence interval [CI] = 0.46 to 1.77). There was no evidence of an association between the use of antioxidant (OR = 1.01, 95% CI = 0.88 to 1.15) or retinol (OR = 0.97, 95% CI = 0.83 to 1.13) supplements and all-cause mortality. Meta-analyses of all other outcomes did not show clear evidence of benefit or harm., Conclusions: The impact of most nutritional interventions cannot be reliably estimated because of the limited number of trials, many of which were of low quality. There is no evidence that dietary modification by cancer patients improves survival and benefits disease prognosis.
- Published
- 2006
- Full Text
- View/download PDF
27. DNA interstrand crosslink repair during G1 involves nucleotide excision repair and DNA polymerase zeta.
- Author
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Sarkar S, Davies AA, Ulrich HD, and McHugh PJ
- Subjects
- DNA Damage, DNA Polymerase III physiology, DNA Replication, DNA-Binding Proteins physiology, DNA-Directed DNA Polymerase physiology, Endodeoxyribonucleases, Enzyme Activation, Nuclear Proteins physiology, Proliferating Cell Nuclear Antigen metabolism, Saccharomyces cerevisiae drug effects, Saccharomyces cerevisiae Proteins physiology, Ubiquitin metabolism, Cross-Linking Reagents pharmacology, DNA Repair, DNA, Fungal drug effects, DNA, Fungal genetics, DNA, Fungal metabolism, G1 Phase, Saccharomyces cerevisiae genetics
- Abstract
The repair mechanisms acting on DNA interstrand crosslinks (ICLs) in eukaryotes are poorly understood. Here, we provide evidence for a pathway of ICL processing that uses components from both nucleotide excision repair (NER) and translesion synthesis (TLS) and predominates during the G1 phase of the yeast cell cycle. Our results suggest that repair is initiated by the NER apparatus and is followed by a thwarted attempt at gap-filling by the replicative Polymerase delta, which likely stalls at the site of the remaining crosslinked oligonucleotide. This in turn leads to ubiquitination of PCNA and recruitment of the damage-tolerant Polymerase zeta that can perform TLS. The ICL repair factor Pso2 acts downstream of the incision step and is not required for Polymerase zeta activation. We show that this combination of NER and TLS is the only pathway of ICL repair available to the cell in G1 phase and is essential for viability in the presence of DNA crosslinks.
- Published
- 2006
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- View/download PDF
28. Sex differences in the association between birth weight and total cholesterol. A meta-analysis.
- Author
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Lawlor DA, Owen CG, Davies AA, Whincup PH, Ebrahim S, Cook DG, and Davey Smith G
- Subjects
- Adolescent, Adult, Aged, Child, Child, Preschool, Cholesterol analysis, Female, Fetal Development physiology, Humans, Male, Middle Aged, Regression Analysis, United Kingdom, Birth Weight, Cholesterol blood, Sex Factors
- Abstract
Purpose: Determine whether a sex difference exists in the association between birth weight and total cholesterol later in life., Methods: Meta-analysis of within-study differences in regression coefficients of cholesterol on birth weight., Results: A total of 34 regression coefficients from 30 studies were included in the analyses; these provided data on 33,650 males and 23,129 females. There was evidence that the inverse association between birth weight and total cholesterol was stronger in males compared to females. The pooled within-study difference in age-adjusted regression coefficients was -0.03 mmol/l (-0.06, -0.01), p = 0.02 and the pooled within-study difference in age and body mass index adjusted regression coefficients was -0.04 mmol/l (-0.07, -0.02), p = 0.002. There was no evidence of heterogeneity in these meta-analyses (both p values > 0.6)., Conclusions: These results provide some evidence for a sex difference in the birth weight-total cholesterol association. This is consistent with studies of fetal growth which suggest that birth size reflects different biological processes for females and males. However, other very large studies are required to confirm this finding.
- Published
- 2006
- Full Text
- View/download PDF
29. SUMO keeps a check on recombination during DNA replication.
- Author
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Ulrich HD, Vogel S, and Davies AA
- Subjects
- Animals, DNA Helicases metabolism, Proliferating Cell Nuclear Antigen metabolism, S Phase, Saccharomyces cerevisiae Proteins metabolism, DNA Replication genetics, Recombination, Genetic genetics, Small Ubiquitin-Related Modifier Proteins metabolism
- Abstract
The small ubiquitin-related modifier SUMO plays an important role in the maintenance of genome stability. Accordingly, DNA replication, repair and recombination factors as well as mediators of chromosome dynamics and cohesion are among its many targets. Attachment of SUMO can modulate the properties of the modified proteins by affecting localization, conformation, stability or enzymatic activity, but often its mechanism of action remains poorly defined. Recent findings demonstrate how SUMO modification of PCNA, the processivity clamp for replicative DNA polymerases, prevents unscheduled recombination during DNA replication by means of directly enhancing physical interactions with an anti-recombinogenic helicase, Srs2. This review highlights how the SUMO conjugation system exerts its effect on the replication fork and discusses the implications for ubiquitin-dependent DNA damage tolerance.
- Published
- 2005
- Full Text
- View/download PDF
30. The RING finger ATPase Rad5p of Saccharomyces cerevisiae contributes to DNA double-strand break repair in a ubiquitin-independent manner.
- Author
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Chen S, Davies AA, Sagan D, and Ulrich HD
- Subjects
- Adenosine Triphosphatases chemistry, Adenosine Triphosphate metabolism, DNA Damage, DNA Helicases, DNA, Single-Stranded metabolism, DNA-Binding Proteins metabolism, Endodeoxyribonucleases metabolism, Exodeoxyribonucleases metabolism, Proliferating Cell Nuclear Antigen metabolism, Protein Structure, Tertiary, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins chemistry, Saccharomyces cerevisiae Proteins metabolism, Ubiquitin-Protein Ligases metabolism, Ubiquitins metabolism, Adenosine Triphosphatases physiology, DNA Repair, Saccharomyces cerevisiae enzymology, Saccharomyces cerevisiae Proteins physiology
- Abstract
Tolerance to replication-blocking DNA lesions is achieved by means of ubiquitylation of PCNA, the processivity clamp for replicative DNA polymerases, by components of the RAD6 pathway. In the yeast Saccharomyces cerevisiae the ubiquitin ligase (E3) responsible for polyubiquitylation of the clamp is the RING finger protein Rad5p. Interestingly, the RING finger, responsible for the protein's E3 activity, is embedded in a conserved DNA-dependent ATPase domain common to helicases and chromatin remodeling factors of the SWI/SNF family. Here, we demonstrate that the Rad5p ATPase domain provides the basis for a function of the protein in DNA double-strand break repair via a RAD52- and Ku-independent pathway mediated by the Mre11/Rad50/Xrs2 protein complex. This activity is distinct and separable from the contribution of the RING domain to ubiquitin conjugation to PCNA. Moreover, we show that the Rad5 protein physically associates with the single-stranded DNA regions at a processed double-strand break in vivo. Our observations suggest that Rad5p is a multifunctional protein that--by means of independent enzymatic activities inherent in its RING and ATPase domains--plays a modulating role in the coordination of repair events and replication fork progression in response to various different types of DNA lesions.
- Published
- 2005
- Full Text
- View/download PDF
31. Crosstalk between SUMO and ubiquitin on PCNA is mediated by recruitment of the helicase Srs2p.
- Author
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Papouli E, Chen S, Davies AA, Huttner D, Krejci L, Sung P, and Ulrich HD
- Subjects
- Chromatin Immunoprecipitation, DNA Helicases genetics, Glutathione Transferase metabolism, Proliferating Cell Nuclear Antigen genetics, Recombinant Fusion Proteins metabolism, SUMO-1 Protein genetics, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins genetics, DNA Helicases metabolism, Proliferating Cell Nuclear Antigen metabolism, Protein Processing, Post-Translational, SUMO-1 Protein metabolism, Saccharomyces cerevisiae Proteins metabolism, Ubiquitin metabolism
- Abstract
Posttranslational modification of proliferating cell nuclear antigen (PCNA), an essential processivity clamp for DNA polymerases, by ubiquitin and SUMO contributes to the coordination of DNA replication, damage tolerance, and mutagenesis. Whereas ubiquitination in response to DNA damage promotes the bypass of replication-blocking lesions, sumoylation during S phase is damage independent. As both modifiers target the same site on PCNA, an antagonistic action of SUMO on ubiquitin-dependent DNA damage tolerance has been proposed. We now present evidence that the apparent negative effect of SUMO on lesion bypass is not due to competition with ubiquitination but is rather mediated by the helicase Srs2p, which affects genome stability by suppressing unscheduled homologous recombination. We show that Srs2p physically interacts with sumoylated PCNA, which contributes to the recruitment of the helicase to replication forks. Our findings suggest a mechanism by which SUMO and ubiquitin cooperatively control the choice of pathway for the processing of DNA lesions during replication.
- Published
- 2005
- Full Text
- View/download PDF
32. Low birth weight is associated with higher adult total cholesterol concentration in men: findings from an occupational cohort of 25,843 employees.
- Author
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Davies AA, Smith GD, Ben-Shlomo Y, and Litchfield P
- Subjects
- Adolescent, Adult, Aged, Body Size, Body Weight, Cohort Studies, England epidemiology, Female, Humans, Hypercholesterolemia epidemiology, Infant, Newborn, Life Style, Male, Menopause, Middle Aged, Sex Factors, Cholesterol blood, Infant, Low Birth Weight
- Abstract
Background: The majority of studies investigating the association between birth weight and adult total cholesterol (TC) concentration have been small and underpowered: not surprisingly, the findings have been inconsistent. We aimed to determine whether birth weight predicted adult TC in a large sample population., Methods and Results: Between 1994 and 1996, 132,000 British Telecom employees undertook voluntary occupational health screening. Birth weight and lifestyle factors were self-reported; TC concentration and body size were measured by occupational health nurses. Complete measurements were available for 18,286 men and 7557 women (age range, 17 to 64 years). We found that sex and birth weight significantly interacted to predict adult TC (birth weight/sex interaction term, P=0.002). In men, lower birth weight was associated with higher adult TC levels (a -0.07 reduction in TC for each 1-kg increase in birth weight; 95% CI, -0.09 to -0.04 mmol/L; P<0.001), whereas no association was observed in women. Adjustment for potential confounding factors, including current body size and menopausal status, did not alter the findings. Analysis by SD score showed that in men, a 1-SD decrease in body mass index lowered TC concentration approximately 5-fold more than a 1-SD increase in birth weight., Conclusions: This is the largest study to investigate the association between birth weight and TC and suggests that the association may be dependent on sex. The absence of an association in women was not explained by menopausal status. The influence of fetal environment on adult TC is small compared with the influence of adult adiposity.
- Published
- 2004
- Full Text
- View/download PDF
33. RAD51 localization and activation following DNA damage.
- Author
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Tarsounas M, Davies AA, and West SC
- Subjects
- Amino Acid Sequence, BRCA2 Protein genetics, DNA Repair genetics, DNA-Binding Proteins genetics, Fluorescent Antibody Technique, Genomic Instability physiology, HeLa Cells, Humans, Molecular Sequence Data, Protein Structure, Tertiary, Rad51 Recombinase, BRCA2 Protein metabolism, DNA Damage physiology, DNA Repair physiology, DNA Replication, DNA-Binding Proteins metabolism, Recombination, Genetic physiology
- Abstract
The efficient repair of double-strand breaks in DNA is critical for the maintenance of genome stability. In response to ionizing radiation and other DNA-damaging agents, the RAD51 protein, which is essential for homologous recombination, relocalizes within the nucleus to form distinct foci that can be visualized by microscopy and are thought to represent sites where repair reactions take place. The formation of RAD51 foci in response to DNA damage is dependent upon BRCA2 and a series of proteins known as the RAD51 paralogues (RAD51B, RAD51C, RAD51D, XRCC2 and XRCC3), indicating that the components present within foci assemble in a carefully orchestrated and ordered manner. By contrast, RAD51 foci that form spontaneously as cells undergo DNA replication at S phase occur without the need for BRCA2 or the RAD51 paralogues. It is known that BRCA2 interacts directly with RAD51 through a series of degenerative motifs known as the BRC repeats. These interactions modulate the ability of RAD51 to bind DNA. Taken together, these observations indicate that BRCA2 plays a critical role in controlling the actions of RAD51 at both the microscopic (focus formation) and molecular (DNA binding) level.
- Published
- 2004
- Full Text
- View/download PDF
34. Micronutrients and fetal growth.
- Author
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Fall CH, Yajnik CS, Rao S, Davies AA, Brown N, and Farrant HJ
- Subjects
- Developing Countries, Female, Fetal Death, Global Health, Humans, Infant, Newborn, Pregnancy, Randomized Controlled Trials as Topic, Embryonic and Fetal Development physiology, Micronutrients, Nutrition Disorders physiopathology, Pregnancy Complications physiopathology, Pregnancy Outcome
- Abstract
Fetal undernutrition affects large numbers of infants in developing countries, with adverse consequences for their immediate survival and lifelong health. It manifests as intrauterine growth retardation (IUGR), defined as birth weight <10th percentile, which probably underestimates the number failing to achieve full growth potential. Birth weight is a crude measure of the dynamic process of fetal growth and does not capture effects of fetal undernutrition on body composition and the development of specific tissues. The link between maternal nutrition and fetal nutrition is indirect. The fetus is nourished by a complex supply line that includes the mother's diet and absorption, endocrine status and metabolism, cardiovascular adaptations to pregnancy and placental function. Micronutrients are essential for growth, and maternal micronutrient deficiency, frequently multiple in developing countries, may be an important cause of IUGR. Supplementation of undernourished mothers with micronutrients has several benefits but there is little hard evidence of improved fetal growth. However, this has been inadequately tested. Most trials have only used single micronutrients and many were inconclusive because of methodological problems. Several food-based studies (some uncontrolled) suggest benefits from improving maternal dietary quality with micronutrient-dense foods. One trial of a multivitamin supplement (HIV-positive mothers, Tanzania) showed increased birth weight and fewer fetal deaths. Well-conducted randomized controlled trials of adequate sample size and including measures of effectiveness are needed in populations at high risk of micronutrient deficiency and IUGR and should include food-based interventions and better measurements of fetal growth, maternal metabolism, and long-term outcomes in the offspring.
- Published
- 2003
- Full Text
- View/download PDF
35. Role of BRCA2 in control of the RAD51 recombination and DNA repair protein.
- Author
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Davies AA, Masson JY, McIlwraith MJ, Stasiak AZ, Stasiak A, Venkitaraman AR, and West SC
- Subjects
- Active Transport, Cell Nucleus, Amino Acid Sequence, BRCA2 Protein, Binding Sites, Breast Neoplasms genetics, Chromatography, Gel, DNA genetics, DNA metabolism, DNA-Binding Proteins antagonists & inhibitors, DNA-Binding Proteins genetics, Female, Humans, Microscopy, Electron, Models, Biological, Molecular Sequence Data, Molecular Weight, Mutation, Neoplasm Proteins chemistry, Neoplasm Proteins genetics, Nucleoproteins antagonists & inhibitors, Nucleoproteins metabolism, Nucleoproteins ultrastructure, Peptide Fragments chemistry, Peptide Fragments pharmacology, Protein Binding, Protein Structure, Tertiary, Rad51 Recombinase, Subcellular Fractions, Substrate Specificity, Transcription Factors chemistry, Transcription Factors genetics, DNA Repair genetics, DNA-Binding Proteins metabolism, Neoplasm Proteins metabolism, Recombination, Genetic, Transcription Factors metabolism
- Abstract
Individuals carrying BRCA2 mutations are predisposed to breast and ovarian cancers. Here, we show that BRCA2 plays a dual role in regulating the actions of RAD51, a protein essential for homologous recombination and DNA repair. First, interactions between RAD51 and the BRC3 or BRC4 regions of BRCA2 block nucleoprotein filament formation by RAD51. Alterations to the BRC3 region that mimic cancer-associated BRCA2 mutations fail to exhibit this effect. Second, transport of RAD51 to the nucleus is defective in cells carrying a cancer-associated BRCA2 truncation. Thus, BRCA2 regulates both the intracellular localization and DNA binding ability of RAD51. Loss of these controls following BRCA2 inactivation may be a key event leading to genomic instability and tumorigenesis.
- Published
- 2001
- Full Text
- View/download PDF
36. Branch migration and Holliday junction resolution catalyzed by activities from mammalian cells.
- Author
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Constantinou A, Davies AA, and West SC
- Subjects
- Animals, Bacterial Proteins metabolism, Cell Fractionation, Cell Line, Cell-Free System, Cricetinae, DNA Repair, DNA-Binding Proteins genetics, Endodeoxyribonucleases genetics, Escherichia coli chemistry, Holliday Junction Resolvases, Humans, Macromolecular Substances, Nucleic Acid Conformation, Rabbits, DNA metabolism, DNA Helicases, DNA-Binding Proteins metabolism, Endodeoxyribonucleases metabolism, Escherichia coli Proteins, Recombination, Genetic
- Abstract
During homologous recombination, DNA strand exchange leads to Holliday junction formation. The movement, or branch migration, of this junction along DNA extends the length of the heteroduplex joint. In prokaryotes, branch migration and Holliday junction resolution are catalyzed by the RuvA and RuvB proteins, which form a complex with RuvC resolvase to form a "resolvasome". Mammalian cell-free extracts have now been fractionated to reveal analogous activities. An ATP-dependent branch migration activity, which migrates junctions through >2700 bp, cofractionates with the Holliday junction resolvase during several chromatographic steps. Together, the two activities promote concerted branch migration/resolution reactions similar to those catalyzed by E. coli RuvABC, highlighting the preservation of this essential pathway in recombination and DNA repair from prokaryotes to mammals.
- Published
- 2001
- Full Text
- View/download PDF
37. The meiosis-specific recombinase hDmc1 forms ring structures and interacts with hRad51.
- Author
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Masson JY, Davies AA, Hajibagheri N, Van Dyck E, Benson FE, Stasiak AZ, Stasiak A, and West SC
- Subjects
- Adenosine Triphosphatases isolation & purification, Cloning, Molecular, DNA Nucleotidyltransferases isolation & purification, DNA, Single-Stranded biosynthesis, DNA, Single-Stranded chemistry, DNA, Viral biosynthesis, DNA, Viral chemistry, DNA-Binding Proteins isolation & purification, Escherichia coli genetics, Gene Library, Humans, Male, Meiosis, Microscopy, Electron, Nucleic Acid Heteroduplexes biosynthesis, Nucleic Acid Heteroduplexes chemistry, Organ Specificity, Rad51 Recombinase, Rec A Recombinases metabolism, Recombinant Proteins chemistry, Recombinant Proteins metabolism, Recombinant Proteins ultrastructure, Recombinases, Recombination, Genetic, Testis enzymology, Adenosine Triphosphatases metabolism, Adenosine Triphosphatases ultrastructure, Cell Cycle Proteins, DNA Nucleotidyltransferases metabolism, DNA Nucleotidyltransferases ultrastructure, DNA-Binding Proteins chemistry, DNA-Binding Proteins metabolism, DNA-Binding Proteins ultrastructure, Integrases
- Abstract
Eukaryotic cells encode two homologs of Escherichia coli RecA protein, Rad51 and Dmc1, which are required for meiotic recombination. Rad51, like E.coli RecA, forms helical nucleoprotein filaments that promote joint molecule and heteroduplex DNA formation. Electron microscopy reveals that the human meiosis-specific recombinase Dmc1 forms ring structures that bind single-stranded (ss) and double-stranded (ds) DNA. The protein binds preferentially to ssDNA tails and gaps in duplex DNA. hDmc1-ssDNA complexes exhibit an irregular, often compacted structure, and promote strand-transfer reactions with homologous duplex DNA. hDmc1 binds duplex DNA with reduced affinity to form nucleoprotein complexes. In contrast to helical RecA/Rad51 filaments, however, Dmc1 filaments are composed of a linear array of stacked protein rings. Consistent with the requirement for two recombinases in meiotic recombination, hDmc1 interacts directly with hRad51.
- Published
- 1999
- Full Text
- View/download PDF
38. Escherichia coli RuvBL268S: a mutant RuvB protein that exhibits wild-type activities in vitro but confers a UV-sensitive ruv phenotype in vivo.
- Author
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Mézard C, George H, Davies AA, van Gool AJ, Zerbib D, Stasiak A, and West SC
- Subjects
- Adenosine Triphosphatases metabolism, Amino Acid Sequence, Bacterial Proteins isolation & purification, Bacterial Proteins metabolism, Base Sequence, DNA chemistry, DNA metabolism, DNA Primers, DNA Topoisomerases, Type I genetics, DNA Topoisomerases, Type I isolation & purification, DNA Topoisomerases, Type I metabolism, Molecular Sequence Data, Mutagenesis, Nucleic Acid Conformation, Phenotype, Protein Binding, Sequence Homology, Amino Acid, Bacterial Proteins genetics, Escherichia coli metabolism, Radiation Tolerance genetics, Ultraviolet Rays
- Abstract
The RuvABC proteins of Escherichia coli process recombination intermediates during genetic recombination and DNA repair. RuvA and RuvB promote branch migration of Holliday junctions, a process that extends heteroduplex DNA. Together with RuvC, they form a RuvABC complex capable of Holliday junction resolution. Branch migration by RuvAB is mediated by RuvB, a hexameric ring protein that acts as an ATP-driven molecular pump. To gain insight into the mechanism of branch migration, random mutations were introduced into the ruvB gene by PCR and a collection of mutant alleles were obtained. Mutation of leucine 268 to serine resulted in a severe UV-sensitive phenotype, characteristic of a ruv defect. Here, we report a biochemical analysis of the mutant protein RuvBL268S. Unexpectedly, the purified protein is fully active in vitro with regard to its ATPase, DNA binding and DNA unwinding activities. It also promotes efficient branch migration in combination with RuvA, and forms functional RuvABC-Holliday junction resolvase complexes. These results indicate that RuvB may perform some additional, and as yet undefined, function that is necessary for cell survival after UV-irradiation.
- Published
- 1999
- Full Text
- View/download PDF
39. Formation of RuvABC-Holliday junction complexes in vitro.
- Author
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Davies AA and West SC
- Subjects
- Bacterial Proteins metabolism, DNA Helicases, DNA-Binding Proteins metabolism, Endodeoxyribonucleases metabolism, Escherichia coli metabolism, Escherichia coli Proteins, Oligodeoxyribonucleotides metabolism
- Abstract
In Escherichia coli, the RuvA, RuvB and RuvC proteins are required for the late stages of homologous recombination and DNA repair. RuvA and RuvB form a complex that interacts with Holliday junctions--crossed DNA structures that are recombination intermediates--and promotes branch migration; RuvC is a junction-specific endonuclease that resolves Holliday junctions and completes the recombination process. Because genetic and biochemical experiments suggest that the processes of branch migration and resolution are linked, coimmunoprecipitation experiments were carried out to determine whether the three Ruv proteins interact to form a functional complex (RuvABC). Using a synthetic Holliday junction, a multisubunit complex containing the junction and RuvA, RuvB and RuvC was detected. In the absence of RuvB, RuvAC-junction complexes were observed. Complex formation was not facilitated by duplex DNA. The identification of a RuvABC-junction complex provides direct evidence that the RuvABC proteins interact at the Holliday junction.
- Published
- 1998
- Full Text
- View/download PDF
40. Biochemical properties of RuvBD113N: a mutation in helicase motif II of the RuvB hexamer affects DNA binding and ATPase activities.
- Author
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Mézard C, Davies AA, Stasiak A, and West SC
- Subjects
- Adenosine Triphosphate metabolism, Amino Acid Sequence, Aspartic Acid, Bacterial Proteins genetics, Bacterial Proteins isolation & purification, Bacterial Proteins metabolism, DNA metabolism, DNA Helicases genetics, DNA-Binding Proteins metabolism, Escherichia coli genetics, Escherichia coli Proteins, Genetic Complementation Test, Hydrolysis, Molecular Sequence Data, Mutagenesis, Site-Directed, Point Mutation, Protein Binding, Protein Conformation, Adenosine Triphosphatases metabolism, Bacterial Proteins chemistry, DNA Helicases chemistry, Recombination, Genetic physiology
- Abstract
Many DNA helicases utilise the energy derived from nucleoside triphosphate hydrolysis to fuel their actions as molecular motors in a variety of biological processes. In association with RuvA, the E. coli RuvB protein (a hexameric ring helicase), promotes the branch migration of Holliday junctions during genetic recombination and DNA repair. To analyse the relationship between ATP-dependent DNA helicase activity and branch migration, a site-directed mutation was introduced into the helicase II motif of RuvB. Over-expression of RuvBD113N in wild-type E. coli resulted in a dominant negative UVs phenotype. The biochemical properties of RuvBD113N were examined and compared with wild-type RuvB in vitro. The single amino acid substitution resulted in major alterations to the biochemical activities of RuvB, such that RuvBD113N was defective in DNA binding and ATP hydrolysis, while retaining the ability to form hexameric rings and interact with RuvA. RuvBD113N formed heterohexamers with wild-type RuvB, and could inhibit RuvB function by affecting its ability to bind DNA. However, heterohexamers exhibited an ability to promote branch migration in vitro indicating that not all subunits of the ring need to be catalytically competent., (Copyright 1997 Academic Press Limited.)
- Published
- 1997
- Full Text
- View/download PDF
41. Role of the Rad1 and Rad10 proteins in nucleotide excision repair and recombination.
- Author
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Davies AA, Friedberg EC, Tomkinson AE, Wood RD, and West SC
- Subjects
- DNA Repair Enzymes, Humans, Single-Strand Specific DNA and RNA Endonucleases, DNA Repair, DNA-Binding Proteins, Endonucleases physiology, Fungal Proteins physiology, Recombination, Genetic, Saccharomyces cerevisiae Proteins
- Abstract
In Saccharomyces cerevisiae, the RAD1 and RAD10 genes are involved in DNA nucleotide excision repair (NER) and in a pathway of mitotic recombination that occurs between direct repeat DNA sequences. In this paper, we show that purified Rad1 and Rad10 interact with a synthetic bubble structure and incise the DNA at the 5'-side of the centrally unpaired region. When Rad1-Rad10 and purified XPG protein (the human homolog of yeast Rad2 protein) were co-incubated with the DNA substrate, we observed incisions at both ends of the bubble. This reaction mimics the dual incision step in nucleotide excision repair in vivo. In addition, the recent suggestion that Rad1 can act to resolve Holliday junctions (Habraken, Y., Sung, P., Prakash, L., and Prakash, S. (1994) Nature 371, 531-534), explaining the recombination defect observed in rad1 mutants, has been further investigated. However, using proteins purified in two different laboratories we were unable to show any interaction between Rad1 and synthetic Holliday junctions. The role that Rad1-Rad10 plays in recombination is likely to resemble its activity in NER by acting upon partially unpaired DNA intermediates such as those formed by recombination mechanisms involving single-strand DNA annealing.
- Published
- 1995
- Full Text
- View/download PDF
42. XPG endonuclease makes the 3' incision in human DNA nucleotide excision repair.
- Author
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O'Donovan A, Davies AA, Moggs JG, West SC, and Wood RD
- Subjects
- Base Sequence, DNA, Single-Stranded metabolism, Escherichia coli, Fungal Proteins metabolism, HeLa Cells, Humans, Molecular Sequence Data, Nucleic Acid Conformation, Recombinant Proteins metabolism, Saccharomyces cerevisiae enzymology, Xeroderma Pigmentosum genetics, DNA Repair, DNA-Binding Proteins, Endodeoxyribonucleases, Endonucleases metabolism, Saccharomyces cerevisiae Proteins, Xeroderma Pigmentosum enzymology
- Abstract
Humans with a defect in the XPG protein suffer from xeroderma pigmentosum (XP) resulting from an inability to perform DNA nucleotide excision repair properly. Here we show that XPG makes a structure-specific endonucleolytic incision in a synthetic DNA substrate containing a duplex region and single-stranded arms. One strand of the duplex is cleaved at the border with single-stranded DNA. A cut with the same polarity is also made in a bubble structure, at the 3' side of the centrally unpaired region. Normal cell extracts introduce a nick 3' to a platinum-DNA lesion, but an XP-G cell extract is defective in making this incision. These data show that XPG has a direct role in making one of the incisions required to excise a damaged oligonucleotide, by cleaving 3' to DNA damage during nucleotide excision repair.
- Published
- 1994
- Full Text
- View/download PDF
43. Resolution of recombination intermediates by a mammalian activity functionally analogous to Escherichia coli RuvC resolvase.
- Author
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Hyde H, Davies AA, Benson FE, and West SC
- Subjects
- Animals, Base Sequence, CHO Cells, Cattle, Chromatography, Affinity, Chromatography, Ion Exchange, Cricetinae, DNA, Viral isolation & purification, DNA, Viral metabolism, Escherichia coli enzymology, Molecular Sequence Data, Nucleotidyltransferases isolation & purification, Oligodeoxyribonucleotides chemical synthesis, Oligodeoxyribonucleotides chemistry, Substrate Specificity, Transposases, Bacterial Proteins metabolism, Endodeoxyribonucleases, Escherichia coli genetics, Escherichia coli metabolism, Escherichia coli Proteins, Nucleotidyltransferases metabolism, Oligodeoxyribonucleotides metabolism, Recombination, Genetic, Thymus Gland metabolism
- Abstract
A mammalian endonuclease that resolves Holliday junctions has been partially purified from extracts of calf thymus and Chinese hamster ovary cells. The activity acts upon (i) synthetic Holliday junctions and (ii) recombination intermediates made by the Escherichia coli RecA protein and appears to be functionally analogous to the E. coli RuvC protein. Cleavage occurs by the introduction of symmetrically related nicks in strands of like polarity to produce nicked duplex DNA products. The nicks can be repaired by DNA ligase. The resolvase is specific for Holliday junctions and does not act upon Y junctions, G/A mismatches, or heterologous loops. The substrate specificity is therefore similar to that of E. coli RuvC protein and contrasts with the broad range specificity of other junction resolvases such as T4 endonuclease VII. The mammalian resolvase activity has been observed at normal levels in extracts prepared from a series of DNA repair-defective cells. These include the x-ray or UV-sensitive hamster lines xrs-5, xrs-6, and Chinese hamster ovary 43-3B (defective in ERCC-1), and murine cells that are severely immunodeficient and defective in both V(D)J rejoining and DNA repair.
- Published
- 1994
44. Tyrosine phosphorylation of alpha tubulin in human T lymphocytes.
- Author
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Ley SC, Verbi W, Pappin DJ, Druker B, Davies AA, and Crumpton MJ
- Subjects
- Amino Acid Sequence, Electrophoresis, Gel, Two-Dimensional, Humans, Molecular Sequence Data, Phosphotyrosine, Precipitin Tests, Tumor Cells, Cultured, Tyrosine analysis, Microtubules chemistry, Phosphoproteins chemistry, T-Lymphocytes chemistry, Tubulin chemistry, Tyrosine analogs & derivatives
- Abstract
N-terminal sequencing of the 55- and 50-kDa polypeptides affinity purified on a phosphotyrosine monoclonal antibody column from activated Jurkat T cells identified alpha and beta tubulin. Two-dimensional gel analysis indicated that alpha tubulin was directly phosphorylated on tyrosine. beta Tubulin was not detectably tyrosine phosphorylated but was precipitated by anti-phosphotyrosine (PTyr) antibody by virtue of its association with the alpha subunit as a heterodimer. Phosphotyrosyl alpha tubulin was not incorporated into intact microtubules and was all in the unpolymerized soluble fraction. These results suggest that tyrosine phosphorylation of alpha tubulin may inhibit the ability of this subunit to polymerize into microtubules. Stimulation of Jurkat T cells via T cell receptor increased the amount of tubulin precipitated by the anti-PTyr antibody. These data raise the possibility that the polymerization of tubulin heterodimers may be regulated by phosphorylation on tyrosine during T cell activation.
- Published
- 1994
- Full Text
- View/download PDF
45. A growth-dependent post-translational modification of annexin VI.
- Author
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Moss SE, Jacob SM, Davies AA, and Crumpton MJ
- Subjects
- 3T3 Cells, Animals, Annexin A6 biosynthesis, Annexin A6 genetics, Cell Line, Growth Substances pharmacology, Humans, Lymphocytes, Mice, Mitotic Index, Phosphorylation, Phosphoserine analysis, Phosphothreonine analysis, Annexin A6 metabolism, Protein Biosynthesis
- Abstract
Annexin VI (p68, 67-kDa calelectrin) is a member of a family of Ca2+/phospholipid-binding proteins, that includes p35 (annexin I) and p36 (annexin II), the major cellular substrates for phosphorylation by the epidermal growth factor receptor and pp60v-src tyrosine kinase activities, respectively. We report here that like annexins I and II, annexin VI is phosphorylated in vivo, but that in contrast, annexin VI phosphorylation is associated with cell growth. In both Swiss 3T3 fibroblasts and human T-lymphoblasts the pattern of phosphorylation followed an almost identical profile. In particular, annexin VI was not phosphorylated in quiescent cells, but was phosphorylated on serine and to a lesser extent threonine, several hours following cell stimulation. Furthermore, annexin VI also incorporated phosphate in a growth-dependent manner, in a form other than a phosphoamino-acid. The phosphate was visualised following acid hydrolysis of immunoprecipitated annexin VI, as part of a complex having high mobility on 2-D thin-layer electrophoresis. The identity of this complex is not known. The results suggest that a post-translational modification other than direct protein phosphorylation may influence the activity of annexin VI and provide evidence linking cell growth with regulation of annexin VI function.
- Published
- 1992
- Full Text
- View/download PDF
46. CD5 is phosphorylated on tyrosine after stimulation of the T-cell antigen receptor complex.
- Author
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Davies AA, Ley SC, and Crumpton MJ
- Subjects
- CD3 Complex, CD5 Antigens, Humans, In Vitro Techniques, Phosphorylation, Phosphotyrosine, Signal Transduction, Time Factors, Tumor Cells, Cultured, Tyrosine analogs & derivatives, Tyrosine metabolism, Antigens, CD metabolism, Antigens, Differentiation, T-Lymphocyte metabolism, Lymphocyte Activation, Receptors, Antigen, T-Cell metabolism, T-Lymphocytes metabolism
- Abstract
When T cells are activated by the T-cell antigen receptor, a number of cellular proteins are phosphorylated on tyrosine. We investigated whether any of these proteins were present on the surface of activated T cells. Using the human leukemic T-cell line Jurkat and normal peripheral blood lymphocytes, we identified a 67-kDa cell surface glycoprotein in anti-phosphotyrosine immunoprecipitates, after treatment of the cells with CD3 antibody. When cell lysates were depleted of CD5 by sequential immunoprecipitation, the 67-kDa phosphotyrosyl polypeptide was no longer precipitated by the phosphotyrosine antibody. Western blot analysis of anti-phosphotyrosine precipitates confirmed that this glycoprotein was CD5. It was possible that CD5 was present in the anti-phosphotyrosine immunoprecipitates due to its physical association with phosphotyrosyl proteins rather than being directly tyrosine-phosphorylated itself. However, Western blot analysis of anti-CD5 immunoprecipitates with phosphotyrosine antibody and phosphoamino acid analysis demonstrated that CD5 was indeed phosphorylated on tyrosine after stimulation of the cells with CD3 antibody and was concomitantly phosphorylated on serine and threonine. Tyrosine phosphorylation of CD5 was maximal 2 min after CD3 stimulation and returned to baseline levels by 60 min. CD5 is expressed on the cell surface of all mature T cells and a small proportion of B lymphocytes and has recently been identified as the ligand for CD72, a receptor present on the surface of all B cells. The present data suggest that tyrosine phosphorylation may be involved in B-cell-T-cell communication.
- Published
- 1992
- Full Text
- View/download PDF
47. The T cell receptor/CD3 complex and CD2 stimulate the tyrosine phosphorylation of indistinguishable patterns of polypeptides in the human T leukemic cell line Jurkat.
- Author
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Ley SC, Davies AA, Druker B, and Crumpton MJ
- Subjects
- Antibodies, Monoclonal pharmacology, CD2 Antigens, CD3 Complex, Cell Line, Electrophoresis, Polyacrylamide Gel, Humans, Immunoblotting, In Vitro Techniques, Phosphorylation, Signal Transduction immunology, Antigens, Differentiation, T-Lymphocyte physiology, Leukemia, T-Cell immunology, Receptors, Antigen, T-Cell immunology, Receptors, Antigen, T-Cell physiology, Receptors, Immunologic physiology, Tyrosine metabolism
- Abstract
Stimulation of the T cell receptor (TcR)/CD3 complex of Jurkat T cells with a monoclonal antibody to the CD3 epsilon chain induced the tyrosine phosphorylation of multiple polypeptides, ranging in size from 21 to 155 kDa. The protein tyrosine phosphorylation was characterized by its rapidity and its transient nature, returning to baseline levels by 60 min. Protein tyrosine kinase activity was also induced when the Jurkat T cells were stimulated with a mitogenic pair of antibodies directed against CD2. Comparison of the polypeptides which were phosphorylated on tyrosine in response to stimulation of the two receptors, by either one- or two-dimensional analysis, failed to reveal any differences. These data suggest that the TcR/CD3 complex and CD2 activated the same tyrosine kinase or kinases. A model is proposed in which CD2 functions as a signal amplifier in physiological responses to antigen/major histocompatibility complex without changing the qualitative nature of the signal generated via the TcR/CD3 complex.
- Published
- 1991
- Full Text
- View/download PDF
48. The human T3 gamma chain is phosphorylated at serine 126 in response to T lymphocyte activation.
- Author
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Davies AA, Cantrell DA, Hexham JM, Parker PJ, Rothbard J, and Crumpton MJ
- Subjects
- Amino Acid Sequence, Antigens, Differentiation, T-Lymphocyte, Enzyme Activation drug effects, Ethers pharmacology, Humans, Ionomycin, Peptide Fragments metabolism, Phorbol 12,13-Dibutyrate, Phorbol Esters pharmacology, Phytohemagglutinins pharmacology, Protein Kinase C metabolism, T-Lymphocytes metabolism, Trypsin, Antigens, Surface, Lymphocyte Activation drug effects, Phosphoserine metabolism, Serine analogs & derivatives, T-Lymphocytes immunology
- Abstract
The gamma subunit of the human T lymphocyte T3 antigen is rapidly phosphorylated on serine residues in vivo during the initiation of T cell activation by a polyclonal mitogen (Phaseolus vulgaris phytohemagglutinin), an activator of protein kinase C (phorbol 12,13-dibutyrate), and an elevator of intracellular calcium (ionomycin). The sites of phosphorylation were identified by comparing tryptic peptide analyses of T3 gamma chains labeled in vivo with various synthetic peptides, corresponding to portions of the cytoplasmic domain of the gamma chain that had been labeled in vitro using purified protein kinase C. Two sites, serines 123 and 126, were phosphorylated in response to ionomycin, whereas a single site, serine 126, was phosphorylated when T lymphocytes were stimulated by P. vulgaris phytohemagglutinin or when protein kinase C was directly activated by phorbol 12,13-dibutyrate. Immune activation of T cells via the protein kinase C pathway thus induces phosphorylation of a single site on the T3 gamma chain, namely serine 126.
- Published
- 1987
49. A new mobile dental clinic.
- Author
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Davies AA
- Subjects
- Dental Equipment, England, Naval Medicine, Dentistry methods, Mobile Health Units
- Published
- 1978
50. Characterization of distinct tyrosine-specific protein kinases in B and T lymphocytes.
- Author
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Earp HS, Austin KS, Gillespie GY, Buessow SC, Davies AA, and Parker PJ
- Subjects
- Cell Line, Chromatography, High Pressure Liquid, Endopeptidases metabolism, Humans, Molecular Weight, Protein-Tyrosine Kinases, Tosyllysine Chloromethyl Ketone pharmacology, B-Lymphocytes enzymology, Protein Kinases blood, Serine Endopeptidases, T-Lymphocytes enzymology
- Abstract
Lymphocyte membrane fractions from both normal and neoplastic sources exhibit tyrosine-specific protein kinase activity. The molecular weights of the endogenous substrates phosphorylated on tyrosine residues differ in B and T cells. To further characterize membrane tyrosine phosphorylation in the two major classes of lymphocytes, the tryptic phosphopeptides of their endogenous substrates were compared and the sensitivity of the kinases to inhibition by N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) was determined. The two major B cell substrates (61,000 and 55,000 daltons, p61 and p55) were gel purified after phosphorylation and exhaustively digested with trypsin. Separation by reverse phase high pressure liquid chromatography demonstrated that these two substrates had two identical phosphotyrosine containing tryptic phosphopeptides. p61 had an additional phosphotyrosine site. Parallel analysis of the two T cell substrates (64,000 and 58,000 daltons, p64 and p58) showed that they also contained two phosphotyrosine sites that were identical. However, the tryptic phosphopeptides from the B and T cell substrate pairs were clearly distinct suggesting that they arise from different gene products. When B and T cell membrane fractions were preincubated with TLCK (21 degrees C, 30 min) a dose-dependent decrease in p64 and p58 phosphorylation resulted. p61 and p55 phosphorylation was not affected at concentrations up to 10 mM TLCK. Tyrosine-specific kinase activity was also assessed by measuring phosphorylation of a tyrosine containing synthetic peptide. The kinase activity of T cell plasma membrane fractions was inhibited by TLCK; the B cell activity was unaffected. The results suggest that membrane fractions from normal and some neoplastic B and T cells have at least two different tyrosine-specific kinases.
- Published
- 1985
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