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Aim: This retrospective study aimed to assess the efficacy of prophylactic antibiotics in preventing ascending cholangitis following Kasai portoenterostomy (KPE). Data from 72 patients treated across four tertiary centres in Israel from 2008 to 2018 were analysed., Methods: Clinical and laboratory data were collected from biliary atresia (BA) diagnosis until liver transplantation (LT) or study completion., Results: Median age at KPE was 58.5 days. Successful KPE was achieved in 23 (32%) patients. Ascending cholangitis occurred in 6/23 (26%) successful KPE cases and 15/45 (33%) unsuccessful cases. Primary antibiotic prophylaxis (49% of patients) was associated with earlier onset of cholangitis (median 77 vs 239 days, p = 0.016). During follow-up, 39% underwent LT, with a 5-year survival with native liver (SNL) of 54%., Conclusion: Prophylactic antibiotics did not reduce cholangitis rates post-KPE in our cohort. Further research is essential to optimise management strategies for infants with BA., (© 2024 The Author(s). Acta Paediatrica published by John Wiley & Sons Ltd on behalf of Foundation Acta Paediatrica.)

Objective: To describe for intervertebral spondylodiscitis (IS) its clinical characteristics, treatment approaches with intravenous (IV) antibiotics, and clinical implications of changes in treatment approach., Study Design: This retrospective study included all children aged 0-18 years diagnosed with imaging-confirmed thoracic and lumbar IS from 2000 to 2022 at a tertiary pediatric hospital. Patients with longer IV treatment regimen were compared with those with a shorter clinically directed IV to oral regimen., Results: In all, 124 cases were included with median age 14.9 months (IQR, 12.7-19.4 months) at diagnosis. Irritability and pain while changing diapers were common symptoms (52.4% and 49.2%, respectively). Elevated erythrocyte sedimentation rate (ESR) was the most common laboratory finding (95%; median, 50 mm/h [IQR 34-64 mm/h]). Elevated erythrocyte sedimentation rate was found in higher proportions (95%) compared with elevated C-reactive protein (76%; median, 1.8 mg/dL; P < .001). Since implementing the shorter clinically directed IV treatment duration for patients with thoracic and lumbar IS, hospitalization duration was decreased from a median of 12 to 8 days (P = .008) and IV treatment duration by a median of 14 to 8 days (P < .001). Only 1 patient (1.6%) in the clinically directed treatment group required rehospitalization owing to failure of therapy. Conversely, 9 of 124 children in the cohort suffered from IV treatment-related complications; all had been treated IV for prolonged periods., Conclusions: Early transition to oral treatment in pediatric spondylodiscitis seems to be appropriate clinically and shortens hospital stay and IV treatment duration without major negative clinical impact., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: Immune Checkpoint Inhibitor (ICI) regimens are approved for first-line treatment of metastatic nononcogene-driven NSCLC. Guidelines do not differentiate which patients with PD-L1 ≥ 50% should receive ICI monotherapy. The clinically validated PROphet NSCLC plasma proteomic-based test is designed to inform this therapeutic decision., Methods: One hundred oncologists were presented with 3 "virtual" metastatic NSCLC cases with PD-L1 scores and asked to recommend an approved first-line regimen. They then watched an online educational webinar on the PROphetNSCLC test. Postwebinar, the same cases were represented with the addition of a PROphet result, and oncologists again recommended a first-line regimen. Responses were compared to assess the impact on first-line treatment selection., Results: Treatment recommendation changed in 39.6% of PROphet-tested cases, with 93% of physicians changing at least 1 case. In the PD-L1 ≥ 50% group, 89% of physicians changed their recommendation, followed by 77%, in PD-L1 < 1%, and 36% in PD-L1 1% to 49%. ​In the PD-L1 ≥ 50%, PROphet POSITIVE group, the recommendation for ICI monotherapy increased from 60% to 89%. ​For the PD-L1 ≥ 50%, PROphet NEGATIVE group, the recommendation for monotherapy dropped from 60% to 9%. In the PD-L1 < 1%, PROphet NEGATIVE group, 35% of patients were spared toxicity from ICI compared to 11% in PROphet untested cases., Conclusion: Adding PROphet to PD-L1 expression impacted therapeutic decision making in first-line NSCLC. PROphet identifies those predicted to have an overall survival benefit from ICI monotherapy versus combination versus chemotherapy, improving the probability of efficacy and reducing toxicity for some patients., Competing Interests: Disclosure DRG receives institutional research grants from Amgen, AstraZeneca, Roche-Genentech, and Merck and consultant and/or advisory board fees from AstraZeneca, Roche-Genentech, Guardant Health, IO Biotech, Oncocyte, Lilly, Merck, and Novartis. He is the Chief Medical Officer for the International Society of Liquid Biopsy. JS receives consultant and/or advisory board fees from AstraZeneca, Jazz, Janssen, Cardinal Health, Cancer ExpertNow, Daiichi Sankyo, Pfizer, and Sanofi. ES receives consultant and/or advisory board fees from AstraZeneca, Regeneron, Sanofi, Bristol Myers Squibb, Abbvie, Janssen, OncoHost, Amgen, Boehringer-Ingelheim, Genentech, G1 Therapeutics, Jazz Pharmaceuticals, Merck, Mirati, Pfizer, Takeda, Sobi, Coherus, Eli Lilly, EMD Serono, and Novartis. MH, YB, CL, IS, and YE, are employees of OncoHost. KM reports consulting fees from OncoHost, Foundation Medicine, Oncocyte, and Aclaris Therapeutics. ARB reports consulting fees from OncoHost., (Copyright © 2024 OncoHost. Published by Elsevier Inc. All rights reserved.)

Purpose: Current guidelines for the management of metastatic non-small cell lung cancer (NSCLC) without driver mutations recommend checkpoint immunotherapy with PD-1/PD-L1 inhibitors, either alone or in combination with chemotherapy. This approach fails to account for individual patient variability and host immune factors and often results in less-than-ideal outcomes. To address the limitations of the current guidelines, we developed and subsequently blindly validated a machine learning algorithm using pretreatment plasma proteomic profiles for personalized treatment decisions., Patients and Methods: We conducted a multicenter observational trial (ClinicalTrials.gov identifier: NCT04056247) of patients undergoing PD-1/PD-L1 inhibitor-based therapy (n = 540) and an additional patient cohort receiving chemotherapy (n = 85) who consented to pretreatment plasma and clinical data collection. Plasma proteome profiling was performed using SomaScan Assay v4.1., Results: Our test demonstrates a strong association between model output and clinical benefit (CB) from PD-1/PD-L1 inhibitor-based treatments, evidenced by high concordance between predicted and observed CB ( R 2 = 0.98, P < .001). The test categorizes patients as either PROphet-positive or PROphet-negative and further stratifies patient outcomes beyond PD-L1 expression levels. The test successfully differentiates between PROphet-negative patients exhibiting high tumor PD-L1 levels (≥50%) who have enhanced overall survival when treated with a combination of immunotherapy and chemotherapy compared with immunotherapy alone (hazard ratio [HR], 0.23 [95% CI, 0.1 to 0.51], P = .0003). By contrast, PROphet-positive patients show comparable outcomes when treated with immunotherapy alone or in combination with chemotherapy (HR, 0.78 [95% CI, 0.42 to 1.44], P = .424)., Conclusion: Plasma proteome-based testing of individual patients, in combination with standard PD-L1 testing, distinguishes patient subsets with distinct differences in outcomes from PD-1/PD-L1 inhibitor-based therapies. These data suggest that this approach can improve the precision of first-line treatment for metastatic NSCLC.

Introduction: Immune checkpoint inhibitors have made a paradigm shift in the treatment of non-small cell lung cancer (NSCLC). However, clinical response varies widely and robust predictive biomarkers for patient stratification are lacking. Here, we characterize early on-treatment proteomic changes in blood plasma to gain a better understanding of treatment response and resistance., Methods: Pre-treatment (T0) and on-treatment (T1) plasma samples were collected from 225 NSCLC patients receiving PD-1/PD-L1 inhibitor-based regimens. Plasma was profiled using aptamer-based technology to quantify approximately 7000 plasma proteins per sample. Proteins displaying significant fold changes (T1:T0) were analyzed further to identify associations with clinical outcomes using clinical benefit and overall survival as endpoints. Bioinformatic analyses of upregulated proteins were performed to determine potential cell origins and enriched biological processes., Results: The levels of 142 proteins were significantly increased in the plasma of NSCLC patients following ICI-based treatments. Soluble PD-1 exhibited the highest increase, with a positive correlation to tumor PD-L1 status, and, in the ICI monotherapy dataset, an association with improved overall survival. Bioinformatic analysis of the ICI monotherapy dataset revealed a set of 30 upregulated proteins that formed a single, highly interconnected network, including CD8A connected to ten other proteins, suggestive of T cell activation during ICI treatment. Notably, the T cell-related network was detected regardless of clinical benefit. Lastly, circulating proteins of alveolar origin were identified as potential biomarkers of limited clinical benefit, possibly due to a link with cellular stress and lung damage., Conclusions: Our study provides insights into the biological processes activated during ICI-based therapy, highlighting the potential of plasma proteomics to identify mechanisms of therapy resistance and biomarkers for outcome., Competing Interests: EJ, GL, BY, YE, IS, ND, MH, CL, YB, MY are employed by Oncohost. RL, AD, YS are consultants of Oncohost. NR and AAm are employed by Asklepios Kliniken GmbH and Asklepios Fachkliniken Muenchen. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from OncoHost. The funder had the following involvement in the study design, collection, analysis, interpretation of data, the writing of this article and the decision to submit it for publication., (Copyright © 2024 Bar, Leibowitz, Reinmuth, Ammendola, Jacob, Moskovitz, Levy-Barda, Lotem, Katsenelson, Agbarya, Abu-Amna, Gottfried, Harkovsky, Wolf, Tepper, Loewenthal, Yellin, Brody, Dahan, Yanko, Lahav, Harel, Raveh Shoval, Elon, Sela, Dicker and Shaked.)

Mitochondria are cellular organelles critical for numerous cellular processes and harboring their own circular mitochondrial DNA (mtDNA). Most mtDNA associated disorders (either deletions, mutations, or depletion) lead to multisystemic disease, often severe at a young age, with no disease-modifying therapies. Mitochondria have a capacity to enter eukaryotic cells and to be transported between cells. We describe a method of ex vivo augmentation of hematopoietic stem and progenitor cells (HSPCs) with normal exogenous mitochondria, termed mitochondrial augmentation therapy (MAT). Here, we show that MAT is feasible and dose dependent, and improves mitochondrial content and oxygen consumption of healthy and diseased HSPCs. Ex vivo mitochondrial augmentation of HSPCs from a patient with a mtDNA disorder leads to superior human engraftment in a non-conditioned NSGS mouse model. Using a syngeneic mouse model of accumulating mitochondrial dysfunction (Polg), we show durable engraftment in non-conditioned animals, with in vivo transfer of mitochondria to recipient hematopoietic cells. Taken together, this study supports MAT as a potential disease-modifying therapy for mtDNA disorders., (© 2021. The Author(s).)

Existing cancer benchmark data sets for human sequencing data use germline variants, synthetic methods, or expensive validations, none of which are satisfactory for providing a large collection of true somatic variation across a whole genome. Here we propose a data set, Lineage derived Somatic Truth (LinST), of short somatic mutations in the HT115 colon cancer cell-line, that are validated using a known cell lineage that includes thousands of mutations and a high confidence region covering 2.7 gigabases per sample.

Splicing and alternative splicing of pre-mRNA are key sources in the formation of diversity in the human proteome. These processes have a central role in the regulation of the gene expression pathway. Yet, how spliceosomes are assembled on a multi-intronic pre-mRNA is at present not well understood. To study the spliceosomes assembled in vivo on transcripts with variable number of introns, we examined a series of three related transcripts derived from the β-globin gene, where two transcript types contained increasing number of introns, while one had only an exon. Each transcript had multiple MS2 sequence repeats that can be bound by the MS2 coat protein. Using our protocol for isolation of endogenous spliceosomes under native conditions from cell nuclei, we show that all three transcripts are found in supraspliceosomes - 21 MDa dynamic complexes, sedimenting at 200S in glycerol gradients, and composed of four native spliceosomes connected by the transcript. Affinity purification of complexes assembled on the transcript with most introns (termed E6), using the MS2 tag, confirmed the assembly of E6 in supraspliceosomes with components such as Sm proteins and PSF. Furthermore, splicing inhibition by spliceostatin A did not inhibit the assembly of supraspliceosomes on the E6 transcript, yet increased the percentage of E6 pre-mRNA supraspliceosomes. These findings were corroborated in intact cells, using RNA FISH to detect the MS2-tagged E6 mRNA, together with GFP-tagged splicing factors, showing the assembly of splicing factors SRSF2, U1-70K, and PRP8 onto the E6 transcripts under normal conditions and also when splicing was inhibited. This study shows that different transcripts with different number of introns, or lacking an intron, are assembled in supraspliceosomes even when splicing is inhibited. This assembly starts at the site of transcription and can continue during the life of the transcript in the nucleoplasm. This study further confirms the dynamic and universal nature of supraspliceosomes that package RNA polymerase II transcribed pre-mRNAs into complexes composed of four native spliceosomes connected by the transcript, independent of their length, number of introns, or splicing state., (Copyright © 2020 Sebbag-Sznajder, Brody, Hochberg-Laufer, Shav-Tal, Sperling and Sperling.)

Background: United Nations (UN) personnel address a diverse range of political, social, and cultural crises throughout the world. Compared with other occupations routinely exposed to traumatic stress, there remains a paucity of research on mental health disorders and access to mental healthcare in this population. To fill this gap, personnel from UN agencies were surveyed for mental health disorders and mental healthcare utilization., Methods: UN personnel ( N = 17 363) from 11 UN entities completed online measures of generalized anxiety disorder (GAD), major depressive disorder (MDD), posttraumatic stress disorder (PTSD), trauma exposure, mental healthcare usage, and socio-demographic information., Results: Exposure to one or more traumatic events was reported by 36.2% of survey responders. Additionally, 17.9% screened positive for GAD, 22.8% for MDD, and 19.9% for PTSD. Employing multivariable logistic regressions, low job satisfaction, younger age (<35 years of age), greater length of employment, and trauma exposure on or off-duty was significantly associated with all the three disorders. Among individuals screening positive for a mental health disorder, 2.05% sought mental health treatment within and 10.01% outside the UN in the past year., Conclusions: UN personnel appear to be at high risk for trauma exposure and screening positive for a mental health disorder, yet a small percentage screening positive for mental health disorders sought treatment. Despite the mental health gaps observed in this study, additional research is needed, as these data reflect a large sample of convenience and it cannot be determined if the findings are representative of the UN., (© The Author(s) 2020.)

Gene expression dynamics can be measured in single living cells. Using a detectable transcriptionally active gene in living cells, we previously found that an mRNA undergoing several splicing events was retained at this gene after transcription until completion of mRNA processing. To determine the reason for this delay in release and whether mRNA retention on the gene might depend on splicing factor availability, we modulated the levels of splicing factors in the nucleus. Increasing the abundance of the diffusing fraction of splicing factors by their overexpression or by Clk1 kinase overexpression to disassemble nuclear speckles, led to a reduction in splicing factor residence times on the active gene, and the retained mRNA was rapidly released from the gene. Other treatments such as overexpression of a mutant inactive Clk1, the downregulation of MALAT1 lncRNA or of the Son protein, or the overexpression of the splicing factor import factor TNPO3, did not affect the dynamics of mRNA release from the gene. We found that the faster release of the mRNA from the gene mediated by increased availability of splicing factors, was dependent on the RS domain of the splicing factors and its phosphorylation state. We propose that the relative abundancies of splicing factors in the nucleoplasm can affect their availability for the splicing events taking place, and regulate the kinetics of mRNA release from the gene after processing., Competing Interests: The authors have declared that no competing interests exist.

Hepatitis C virus (HCV) infection is the leading cause of chronic hepatitis, which often results in liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC). HCV possesses an RNA genome and its replication is confined to the cytoplasm. Yet, infection with HCV leads to global changes in gene expression, and chromosomal instability (CIN) in the host cell. The mechanisms by which the cytoplasmic virus affects these nuclear processes are elusive. Here, we show that HCV modulates the function of the Structural Maintenance of Chromosome (SMC) protein complex, cohesin, which tethers remote regions of chromatin. We demonstrate that infection of hepatoma cells with HCV leads to up regulation of the expression of the RAD21 cohesin subunit and changes cohesin residency on the chromatin. These changes regulate the expression of genes associated with virus-induced pathways. Furthermore, siRNA downregulation of viral-induced RAD21 reduces HCV infection. During mitosis, HCV infection induces hypercondensation of chromosomes and the appearance of multi-centrosomes. We provide evidence that the underlying mechanism involves the viral NS3/4 protease and the cohesin regulator, WAPL. Altogether, our results provide the first evidence that HCV induces changes in gene expression and chromosome structure of infected cells by modulating cohesin., (© The Author(s) 2019. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: Wikipedia is one of the most consulted health resources in the world. Since the public is using health information from Wikipedia to make health care decisions, improving the quality of that health information is in the public interest. The open editable content design of Wikipedia and quality control processes in place provide an opportunity to add high-value, evidence-based information and take an active role in improving the health care information infrastructure., Objective: The aim of this project was to enhance Wikipedia health pages using high-quality, current research findings and track the persistence of those edits and number of page views after the changes to assess the reach of this initiative., Methods: We conducted Wikipedia Editathons with 3 different cohorts of Physical Therapy (PT) students to add high-quality health information to existing Wikipedia pages. Students synthesized best evidence information and updated and/or corrected existing Wikipedia entries on specific health pages. To evaluate the impact of these contributions, we examined two factors: (1) response to our contributions from the Wikipedia editing community, including number and type of subsequent edits as well as persistence of the student contributions and (2) number of page views by the public from the time of the page edits., Results: A total of 98 PT students in 3 different cohorts engaged in Editathons, editing 24 health pages. Of the 24 edits, 22 persisted at the end of the observation period (from time of entry to May 31, 2018) and received nearly 8 million page views. Each health page had an average of 354,724 page views., Conclusions: The Wikipedia Editathon is an effective way to continuously enhance the quality of health information available on Wikipedia. It is also an excellent way of bridging health technology with best-evidence medical facts and disseminating accurate, useful information to the public., (©Shira Schecter Weiner, Jill Horbacewicz, Lane Rasberry, Yocheved Bensinger-Brody. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 18.03.2019.)

Mutation data reveal the dynamic equilibrium between DNA damage and repair processes in cells and are indispensable to the understanding of age-related diseases, tumor evolution, and the acquisition of drug resistance. However, available genome-wide methods have a limited ability to resolve rare somatic variants and the relationships between these variants. Here, we present lineage sequencing, a new genome sequencing approach that enables somatic event reconstruction by providing quality somatic mutation call sets with resolution as high as the single-cell level in subject lineages. Lineage sequencing entails sampling single cells from a population and sequencing subclonal sample sets derived from these cells such that knowledge of relationships among the cells can be used to jointly call variants across the sample set. This approach integrates data from multiple sequence libraries to support each variant and precisely assigns mutations to lineage segments. We applied lineage sequencing to a human colon cancer cell line with a DNA polymerase epsilon ( POLE ) proofreading deficiency (HT115) and a human retinal epithelial cell line immortalized by constitutive telomerase expression (RPE1). Cells were cultured under continuous observation to link observed single-cell phenotypes with single-cell mutation data. The high sensitivity, specificity, and resolution of the data provide a unique opportunity for quantitative analysis of variation in mutation rate, spectrum, and correlations among variants. Our data show that mutations arrive with nonuniform probability across sublineages and that DNA lesion dynamics may cause strong correlations between certain mutations., (© 2018 Brody et al.; Published by Cold Spring Harbor Laboratory Press.)

Microsatellites (MSs) are tracts of variable-length repeats of short DNA motifs that exhibit high rates of mutation in the form of insertions or deletions (indels) of the repeated motif. Despite their prevalence, the contribution of somatic MS indels to cancer has been largely unexplored, owing to difficulties in detecting them in short-read sequencing data. Here we present two tools: MSMuTect, for accurate detection of somatic MS indels, and MSMutSig, for identification of genes containing MS indels at a higher frequency than expected by chance. Applying MSMuTect to whole-exome data from 6,747 human tumors representing 20 tumor types, we identified >1,000 previously undescribed MS indels in cancer genes. Additionally, we demonstrate that the number and pattern of MS indels can accurately distinguish microsatellite-stable tumors from tumors with microsatellite instability, thus potentially improving classification of clinically relevant subgroups. Finally, we identified seven MS indel driver hotspots: four in known cancer genes (ACVR2A, RNF43, JAK1, and MSH3) and three in genes not previously implicated as cancer drivers (ESRP1, PRDM2, and DOCK3).

The transcriptional kinetics of RNA polymerase II, the enzyme responsible for mRNA transcription in the nucleoplasm, can be modulated by a variety of factors. It is therefore important to establish experimental systems that will enable the readout of transcription kinetics of specific genes as they occur in real time within individual cells. This can be performed by implementing fluorescent tagging of the mRNA under live-cell conditions. This chapter describes how to generate fluorescently tagged genes and mRNA, and how a photobleaching approach can produce information on mRNA transcription kinetics., (Copyright © 2017 Elsevier Inc. All rights reserved.)

RNA processing by the splicing machinery removes intronic sequences from pre-mRNA to generate mature mRNA transcripts. Many splicing events occur co-transcriptionally when the pre-mRNA is still associated with the transcription machinery. This mechanism raises questions regarding the number of spliceosomes associated with the pre-mRNA at a given time. In this protocol, we present a quantitative FISH approach that measures the ratio of intensities between two different spliceosomal components associated on a nascent mRNA, and compares to the number of introns in the mRNA, thereby calculating the number of spliceosome complexes assembled with each transcript.

Splicing can occur co-transcriptionally. What happens when the splicing reaction lags after the completed transcriptional process? We found that elongation rates are independent of ongoing splicing on the examined genes and suggest that when transcription has completed but splicing has not, the splicing machinery is retained at the site of transcription, independently of the polymerase.

The transcriptional activity of RNA polymerase II (Pol II) is a dynamic process and therefore measuring the kinetics of the transcriptional process in vivo is of importance. Pol II kinetics have been measured using biochemical or molecular methods. In recent years, with the development of new visualization methods, it has become possible to follow transcription as it occurs in real time in single living cells. Herein we describe how to perform analysis of Pol II elongation kinetics on a specific gene in living cells. Using a cell line in which a specific gene locus (DNA), its mRNA product, and the final protein product can be fluorescently labeled and visualized in vivo, it is possible to detect the actual transcription of mRNAs on the gene of interest. The mRNA is fluorescently tagged using the MS2 system for tagging mRNAs in vivo, where the 3'UTR of the mRNA transcripts contain 24 MS2 stem-loop repeats, which provide highly specific binding sites for the YFP-MS2 coat protein that labels the mRNA as it is transcribed. To monitor the kinetics of transcription we use the Fluorescence Recovery After Photobleaching (FRAP) method. By photobleaching the YFP-MS2-tagged nascent transcripts at the site of transcription and then following the recovery of this signal over time, we obtain the synthesis rate of the newly made mRNAs. In other words, YFP-MS2 fluorescence recovery reflects the generation of new MS2 stem-loops in the nascent transcripts and their binding by fluorescent free YFP-MS2 molecules entering from the surrounding nucleoplasm. The FRAP recovery curves are then analyzed using mathematical mechanistic models formalized by a series of differential equations, in order to retrieve the kinetic time parameters of transcription.

RNA processing events that take place on the transcribed pre-mRNA include capping, splicing, editing, 3' processing, and polyadenylation. Most of these processes occur co-transcriptionally while the RNA polymerase II (Pol II) enzyme is engaged in transcriptional elongation. How Pol II elongation rates are influenced by splicing is not well understood. We generated a family of inducible gene constructs containing increasing numbers of introns and exons, which were stably integrated in human cells to serve as actively transcribing gene loci. By monitoring the association of the transcription and splicing machineries on these genes in vivo, we showed that only U1 snRNP localized to the intronless gene, consistent with a splicing-independent role for U1 snRNP in transcription. In contrast, all snRNPs accumulated on intron-containing genes, and increasing the number of introns increased the amount of spliceosome components recruited. This indicates that nascent RNA can assemble multiple spliceosomes simultaneously. Kinetic measurements of Pol II elongation in vivo, Pol II ChIP, as well as use of Spliceostatin and Meayamycin splicing inhibitors showed that polymerase elongation rates were uncoupled from ongoing splicing. This study shows that transcription elongation kinetics proceed independently of splicing at the model genes studied here. Surprisingly, retention of polyadenylated mRNA was detected at the transcription site after transcription termination. This suggests that the polymerase is released from chromatin prior to the completion of splicing, and the pre-mRNA is post-transcriptionally processed while still tethered to chromatin near the gene end., Competing Interests: The authors have declared that no competing interests exist.

Precursor messenger RNA (pre-mRNA) splicing is catalyzed by the spliceosome, a large ribonucleoprotein (RNP) complex composed of five small nuclear RNP particles (snRNPs) and additional proteins. Using live cell imaging of GFP-tagged snRNP components expressed at endogenous levels, we examined how the spliceosome assembles in vivo. A comprehensive analysis of snRNP dynamics in the cell nucleus enabled us to determine snRNP diffusion throughout the nucleoplasm as well as the interaction rates of individual snRNPs with pre-mRNA. Core components of the spliceosome, U2 and U5 snRNPs, associated with pre-mRNA for 15-30 s, indicating that splicing is accomplished within this time period. Additionally, binding of U1 and U4/U6 snRNPs with pre-mRNA occurred within seconds, indicating that the interaction of individual snRNPs with pre-mRNA is distinct. These results are consistent with the predictions of the step-wise model of spliceosome assembly and provide an estimate on the rate of splicing in human cells.

The flow of genetic information in eukaryotic cells occurs through the nucleocytoplasmic translocation of mRNAs. Knowledge of in vivo messenger RNA export kinetics remains poor in comparison with that of protein transport. We have established a mammalian system that allowed the real-time visualization and quantification of large single mRNA-protein complexes (mRNPs) during export. The in vivo dynamics of bulk mRNP transport and export, from transcription to the nuclear pore complex (NPC), occurred within a 5-40 minute time frame, with no NPC pile-up. mRNP export was rapid (about 0.5 s) and kinetically faster than nucleoplasmic diffusion. Export inhibition demonstrated that mRNA-NPC interactions were independent of ongoing export. Nucleoplasmic transport dynamics of intron-containing and intronless mRNAs were similar, yet an intron did increase export efficiency. Here we provide visualization and analysis at the single mRNP level of the various steps in nuclear gene expression and the inter-chromatin tracks through which mRNPs diffuse, and demonstrate the kinetics of mRNP-NPC interactions and translocation.

Nuclear transcribed genes produce mRNA transcripts destined to travel from the site of transcription to the cytoplasm for protein translation. Certain transcripts can be further localized to specific cytoplasmic regions. We examined the life cycle of a transcribed beta-actin mRNA throughout gene expression and localization, in a cell system that allows the in vivo detection of the gene locus, the transcribed mRNAs and the cytoplasmic beta-actin protein that integrates into the actin cytoskeleton. Quantification showed that RNA polymerase II elongation progressed at a rate of 3.3 kb/minute and that transactivator binding to the promoter was transient (40 seconds), and demonstrated the unique spatial structure of the coding and non-coding regions of the integrated gene within the transcription site. The rates of gene induction were measured during interphase and after mitosis, demonstrating that daughter cells were not synchronized in respect to transcription initiation of the studied gene. Comparison of the spatial and temporal kinetics of nucleoplasmic and cytoplasmic mRNA transport showed that the beta-actin-localization response initiates from the existing cytoplasmic mRNA pool and not from the newly synthesized transcripts arising after gene induction. It was also demonstrated that mechanisms of random movement were predominant in mediating the efficient translocation of mRNA in the eukaryotic cell.

Exported mRNAs are targeted for translation or can undergo degradation by several decay mechanisms. The 5'-->3' degradation machinery localizes to cytoplasmic P bodies (PBs). We followed the dynamic properties of PBs in vivo and investigated the mechanism by which PBs scan the cytoplasm. Using proteins of the decapping machinery, we asked whether PBs actively scan the cytoplasm or whether a diffusion-based mechanism is sufficient. Live-cell imaging showed that PBs were anchored mainly to microtubules. Quantitative single-particle tracking demonstrated that most PBs exhibited spatially confined motion dependent on microtubule motion, whereas stationary PB pairs were identified at the centrosome. Some PBs translocated in long-range movements on microtubules. PB mobility was compared with mitochondria, endoplasmic reticulum, peroxisomes, SMN bodies, and stress granules, and diffusion coefficients were calculated. Disruption of the microtubule network caused a significant reduction in PB mobility together with an induction of PB assembly. However, FRAP measurements showed that the dynamic flux of assembled PB components was not affected by such treatments. FRAP analysis showed that the decapping enzyme Dcp2 is a nondynamic PB core protein, whereas Dcp1 proteins continuously exchanged with the cytoplasm. This study reveals the mechanism of PB transport, and it demonstrates how PB assembly and disassembly integrate with the presence of an intact cytoskeleton.

The mechanism underlying the important role of protein kinase Cdelta (PKCdelta) in the apoptotic effect of etoposide in glioma cells is incompletely understood. Here, we examined the role of PKCdelta in the activation of Erk1/2 by etoposide. We found that etoposide induced persistent activation of Erk1/2 and nuclear translocation of phospho-Erk1/2. MEK1 inhibitors decreased the apoptotic effect of etoposide, whereas inhibitors of p38 and JNK did not. The activation of Erk1/2 by etoposide was downstream of PKCdelta since the phosphorylation of Erk1/2 was inhibited by a PKCdelta-KD mutant and PKCdelta small interfering RNA. We recently reported that phosphorylation of PKCdelta on tyrosines 64 and 187 was essential for the apoptotic effect of etoposide. Using PKCdeltatyrosine mutants, we found that the phosphorylation of PKCdeltaon these tyrosine residues, but not on tyrosine 155, was also essential for the activation of Erk1/2 by etoposide. In contrast, nuclear translocation of PKCdelta was independent of its tyrosine phosphorylation and not necessary for the phosphorylation of Erk1/2. Etoposide induced down-regulation of kinase phosphatase-1 (MKP-1), which correlated with persistent phosphorylation of Erk1/2 and was dependent on the tyrosine phosphorylation of PKCdelta. Moreover, silencing of MKP-1 increased the phosphorylation of Erk1/2 and the apoptotic effect of etoposide. Etoposide induced polyubiquitylation and degradation of MKP-1 that was dependent on PKCdelta and on its tyrosine phosphorylation. These results indicate that distinct phosphorylation of PKCdeltaon tyrosines 64 and 187 specifically activates the Erk1/2 pathway by the down-regulation of MKP-1, resulting in the persistent phosphorylation of Erk1/2 and cell apoptosis.

We imaged transcription in living cells using a locus-specific reporter system, which allowed precise, single-cell kinetic measurements of promoter binding, initiation and elongation. Photobleaching of fluorescent RNA polymerase II revealed several kinetically distinct populations of the enzyme interacting with a specific gene. Photobleaching and photoactivation of fluorescent MS2 proteins used to label nascent messenger RNAs provided sensitive elongation measurements. A mechanistic kinetic model that fits our data was validated using specific inhibitors. Polymerases elongated at 4.3 kilobases min(-1), much faster than previously documented, and entered a paused state for unexpectedly long times. Transcription onset was inefficient, with only 1% of polymerase-gene interactions leading to completion of an mRNA. Our systems approach, quantifying both polymerase and mRNA kinetics on a defined DNA template in vivo with high temporal resolution, opens new avenues for studying regulation of transcriptional processes in vivo.

The doublecortin-like (DCX) domains serve as protein-interaction platforms. DCX tandem domains appear in the product of the X-linked doublecortin (DCX) gene, in retinitis pigmentosa-1 (RP1), as well as in other gene products. Mutations in the human DCX gene are associated with abnormal neuronal migration, epilepsy, and mental retardation; mutations in RP1 are associated with a form of inherited blindness, while DCDC2 has been associated with dyslectic reading disabilities. Motivated by the possible importance of this gene family, a thorough analysis to detect all family members in the mouse was conducted. The DCX-repeat gene superfamily is composed of eleven paralogs, and we cloned the DCX domains from nine different genes. Our study questioned which functions attributed to the DCX domain, are conserved among the different members. Our results suggest that the proteins with the DCX-domain have conserved and unique roles in microtubule regulation and signal transduction. All the tested proteins stimulated microtubule assembly in vitro. Proteins with tandem repeats stabilized the microtubule cytoskeleton in transfected cells, while those with single repeats localized to actin-rich subcellular structures, or the nucleus. All tested proteins interacted with components of the JNK/MAP-kinase pathway, while only a subset interacted with Neurabin 2, and a nonoverlapping group demonstrated actin association. The sub-specialization of some members due to confined intracellular localization, and protein interactions may explain the success of this superfamily.

Although many empirical studies have documented the range and severity of problems caused by psychopaths, considerably less attention has focused on understanding its origins. Efforts to treat this potentially dangerous population have been equally frustrating, as psychotherapeutic approaches have almost always proven ineffectual. Because of the limited understanding of the psychological and interpersonal dynamics underlying psychopathy, the authors sought to assess the extent to which object relations theory could inform our understanding of psychopathy. In addition to eliciting background information, 74 men sentenced to probation following a criminal conviction were assessed using the Psychopathy Checklist: Screening Version, a clinician-rated measure of psychopathy, and were administered the BORI, a self-report measure of object relations. Results showed significant correlations between object relations dimensions, psychopathy scores, and childhood environment data. Furthermore, object relations scores added to the prediction of psychopathy even after demographic and behavioral variables were considered, suggesting that object relations deficits comprise a significant component of psychopathy. Results suggest that psychopaths harbor profound underlying psychosocial damage including intense anxiety, anger, bitterness, and resentment. Implications for interventions and future research are discussed.