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Sulfenyl dipyrroles feature two pyrroles linked via a sulfenyl bridge. The synthesis of sulfenyl dipyrroles has typically involved [SCl.sub.2] as the sulfur source. However, [SCl.sub.2] is no longer readily available within North America and Europe. Herein we report a new synthesis of sulfenyl dipyrroles using [SOCl.sub.2] as the sulfur source and reductant. Although five new sulfenyl dipyrroles were synthesized and isolated via this route, functional group tolerance proved limited. A potential mechanism for the reaction, involving reduction of a sulfinyl moiety by [SOCl.sub.2], is briefly explored. Key words: sulfur, pyrrole, organic synthesis, in-situ reduction of sulfinyl dipyrroles. Les sulfenyldipyrroles sont constituees de deux pyrroles relies par un pont sulfenyle. Dans la synthese des sulfenyldipyrroles, le [SCl.sub.2] est habituellement employe comme source de soufre. Or, le [SCl.sub.2] n'est plus facilement accessible en Amerique du Nord et en Europe. Dans cet article, nous presentons une nouvelle synthese des sulfenyldipyrroles qui fait intervenir le [SOCl.sub.2] comme source de soufre et comme agent reducteur. Bien que nous soyons parvenus a synthetiser et a isoler cinq nouveaux sulfenyldipyrroles par cette methode, la tolerance des groupes fonctionnels s'est revelee limitee. Nous avons explore un mecanisme de reaction possible, qui impliquerait la reduction d'une fraction sulfinyle par le [SOCl.sub.2]. [Traduit par la Redaction] Mots-cles : soufre, pyrrole, synthese organique, reduction in situ des sulfinyldipyrroles., Introduction The sulfenyl dipyrrolic motif, featuring two pyrroles linked via a sulfenyl bridge (1, V = S, Fig.1), has been known since the 1930s. (1) The most common application of [...]

Polymerase [delta] is essential for eukaryotic genome duplication and synthesizes DNA at both the leading and lagging strands. The polymerase [delta] complex is a heterotetramer comprising the catalytic subunit POLD1 and the accessory subunits POLD2, POLD3, and POLD4. Beyond DNA replication, the polymerase [delta] complex has emerged as a central element in genome maintenance. The essentiality of polymerase [delta] has constrained the generation of polymerase [delta]-knockout cell lines or model organisms and, therefore, the understanding of the complexity of its activity and the function of its accessory subunits. To our knowledge, no germline biallelic mutations affecting this complex have been reported in humans. In patients from 2 independent pedigrees, we have identified what we believe to be a novel syndrome with reduced functionality of the polymerase [delta] complex caused by germline biallelic mutations in POLD1 or POLD2 as the underlying etiology of a previously unknown autosomal-recessive syndrome that combines replicative stress, neurodevelopmental abnormalities, and immunodeficiency. Patients' cells showed impaired cell-cycle progression and replication-associated DNA lesions that were reversible upon overexpression of polymerase [delta]. The mutations affected the stability and interactions within the polymerase [delta] complex or its intrinsic polymerase activity. We believe our discovery of human polymerase [delta] deficiency identifies the central role of this complex in the prevention of replication-related DNA lesions, with particular relevance to adaptive immunity., Introduction Eukaryotic genome duplication relies on 3 B-family DNA polymerases: polymerase [alpha], polymerase [epsilon], and polymerase [delta] (1). Polymerase [alpha] is known to have primase activity (2), whereas polymerase [epsilon] [...]

The synthesis of symmetric [alpha]-free meso-H-dipyrrin hydrobromides from 5-H-2-formyl pyrroles was investigated. The self-condensation produces regioisomeric dipyrrins through adoption of two mechanistic pathways. The key difference between the two pathways lies in which position of the pyrrole directs nucleophilic attack. Through a systematic study involving various substituted and (or) isotopically labelled 5-H-2-formyl pyrroles, we herein provide evidence to suggest that not only do two mechanistic pathways exist, but the steric bulk of the substituent adjacent to the 5-unsubstituted position influences which pathway dominates. Key words: dipyrrins, pyrroles, steric effects, condensation, synthesis. Nous avons etudie la synthese de bromhydrates de meso-H-dipyrrine symetriques non substituees a la position [ALPHA] a partir de 5-H-2-formylpyrroles. Ceux-ci subissent une autocondensation pour former des dipyrrines regio-isomeriques par deux voies mecanistiques differentes. La principale difference entre ces deux voies reside dans la position du pyrrole qui dirige l'attaque nucleophile. Au moyen d'une etude systematique faisant appel a une serie de 5-H-2-formylpyrroles substitues et/ou marques d'un isotope, nous faisons la demonstration non seulement qu'il existe deux voies mecanistiques, mais que l'encombrement sterique du substituant adjacent a la position 5 non substituee a une incidence sur la voie privilegiee. [Traduit par la Redaction] Mots-cles : dipyrrines, pyrroles, effets steriques, condensation, synthese., Introduction Although historically used as a building block for porphyrins, (1) in recent years the dipyrrinato unit (2-6) (Fig. 1) has come to be appreciated as a useful chromophore by [...]

* Once obscure, Zika virus (ZIKV) has attracted significant medical and scientific attention in the past year because of large outbreaks associated with the recent introduction of this virus into the Western hemisphere. In particular, the occurrence of severe congenital infections and cases of Guillain-Barre syndrome has placed this virus squarely in the eyes of clinical and anatomic pathologists. This review article provides a basic introduction to ZIKV, its genetics, its structural characteristics, and its biology. A multidisciplinary effort will be essential to establish clinicopathologic correlations of the basic virology of ZIKV in order to advance development of diagnostics, therapeutics, and vaccines. (Arch Pathol Lab Med. 2017;141:33-42; doi: 10.5858/arpa.2016-0409-RA), First identified in 1947 in rhesus macaques in the Zika forest near Kampala, Uganda, (1) Zika virus (ZIKV) received little attention in the medical literature through the 20th century. Few [...]

Abstract: An indole ring system is considered as a versatile scaffold in the pharmaceutical field. In this article, comparative QSAR modeling (2D-QSAR, 3D-QSAR; kNN-MFA and CoMSIA) was performed on some [...]

The origin of mutations is central to understanding evolution and of key relevance to health. Variation occurs non-randomly across the genome, and mechanisms for this remain to be defined. Here we report that the 5' ends of Okazaki fragments have significantly increased levels of nucleotide substitution, indicating a replicative origin for such mutations. Using a novel method, emRiboSeq, we map the genome-wide contribution of polymerases, and show that despite Okazaki fragment processing, DNA synthesized by error-prone polymerase-[alpha] (Pol-[alpha]) is retained in vivo, comprising approximately 1.5% of the mature genome. We propose that DNA-binding proteins that rapidly re-associate post-replication act as partial barriers to Pol-[delta]-mediated displacement of Pol-[alpha]-synthesized DNA, resulting in incorporation of such Pol-[alpha] tracts and increased mutation rates at specific sites. We observe a mutational cost to chromatin and regulatory protein binding, resulting in mutation hotspots at regulatory elements, with signatures of this process detectable in both yeast and humans. The emRiboSeq sequencing method is used to track polymerase activity genome-wide in vivo; despite Okazaki fragment processing, DNA synthesized by error-prone polymerase-[alpha] (Pol-[alpha]) is retained in vivo and comprises ~1.5% of the genome, establishing Pol-[alpha] as an important source of genomic variability and providing a mechanism for site-specific variation in nucleotide substitution rates. Replication-linked genome variation The mechanisms that underpin non-random distribution of mutations across the genome remain to be defined. Here Andrew Jackson and colleagues report that the 5' ends of Okazaki fragments -- short fragments of DNA synthesized on the lagging strand of DNA during replication -- have increased levels of nucleotide substitution. With the help of a newly developed method tracking polymerase activity known as emRiboSeq, they show that despite Okazaki fragment processing, DNA synthesized by error-prone polymerase-[alpha] (Pol-[alpha]) is retained in vivo, and comprises about 1.5% of the genome. These findings establish establishing Pol-[alpha] as an important source of genomic variability, and provide a mechanism for site-specific variation in nucleotide substitution rates. Mutation hotspots at regulatory elements are therefore a mutational cost of chromatin and regulatory protein binding., Author(s): Martin A. M. Reijns [sup.1] , Harriet Kemp [sup.2] , James Ding [sup.1] , Sophie Marion de Procé [sup.2] , Andrew P. Jackson [sup.1] , Martin S. Taylor [sup.2] [...]

The origin of mutations is central to understanding evolution and of key relevance to health. Variation occurs non-randomly across the genome, and mechanisms for this remain to be defined. Here we report that the 5' ends of Okazaki fragments have significantly increased levels of nucleotide substitution, indicating a replicative origin for such mutations. Using a novel method, emRiboSeq, we map the genome-wide contribution of polymerases, and show that despite Okazaki fragment processing, DNA synthesized by error-prone polymerase- α (Pol-α) is retained in vivo, comprising approximately 1.5% of the mature genome. We propose that DNA-binding proteins that rapidly re-associate post-replication act as partial barriers to Pol-δ-mediated displacement of Pol-α-synthesized DNA, resulting in incorporation of such Pol-α tracts and increased mutation rates at specific sites. We observe a mutational cost to chromatin and regulatory protein binding, resulting in mutation hotspots at regulatory elements, with signatures of this process detectable in both yeast and humans., Mutations occur despite the exquisite fidelity of DNA replication, efficient proofreading and mismatch repair (1), resulting in heritable disease and providing the raw material for evolution. Genome variation is non-uniform [...]

Medulloblastomas are the most common malignant brain tumours in children (1). Identifying and understanding the genetic events that drive these tumours is critical for the development of more effective diagnostic, [...]

Once obscure, Zika virus (ZIKV) has attracted significant medical and scientific attention in the past year because of large outbreaks associated with the recent introduction of this virus into the Western hemisphere. In particular, the occurrence of severe congenital infections and cases of Guillain-Barre syndrome has placed this virus squarely in the eyes of clinical and anatomic pathologists. This review article provides a basic introduction to ZIKV, its genetics, its structural characteristics, and its biology. A multidisciplinary effort will be essential to establish clinico-pathologic correlations of the basic virology of ZIKV in order to advance development of diagnostics, therapeutics, and vaccines. doi: 10.5858/arpa.2016-0409-RA, First identified in 1947 in rhesus macaques in the Zika forest near Kampala, Uganda, (1) Zika virus (ZIKV) received little attention in the medical literature through the 20th century. Few [...]

Background The catalytically active 66-kDa subunit of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) consists of DNA polymerase, connection, and ribonuclease H (RNase H) domains. Almost all known RT inhibitor resistance mutations identified to date map to the polymerase domain of the enzyme. However, the connection and RNase H domains are not routinely analysed in clinical samples and none of the genotyping assays available for patient management sequence the entire RT coding region. The British Columbia Centre for Excellence in HIV/AIDS (the Centre) genotypes clinical isolates up to codon 400 in RT, and our retrospective statistical analyses of the Centre's database have identified an N3481 mutation in the RT connection domain in treatment-experienced individuals. The objective of this multidisciplinary study was to establish the in vivo relevance of this mutation and its role in drug resistance. Methods and Findings The prevalence of N3481 in clinical isolates, the time taken for it to emerge under selective drug pressure, and its association with changes in viral load, specific drug treatment, and known drug resistance mutations was analysed from genotypes, viral loads, and treatment histories from the Centre's database. N3481 increased in prevalence from below 1% in 368 treatmentnaive individuals to 12.1% in 1,009 treatment-experienced patients (p = 7.7 x 10-12). N3481 appeared early in therapy and was highly associated with thymidine analogue mutations (TAMS) M41 L and T215Y/F (p < 0.001), the lamivudine resistance mutations M1 84V/1 (p < 0.001), and non-nucleoside RTI (NNRTI) resistance mutations K1 03N and Y181C/I (p < 0.001). The association with TAMS and NNRTI resistance mutations was consistent with the selection of N3481 in patients treated with regimens that included both zidovudine and nevirapine (odds ratio 2.62, 95% confidence interval 1.43-4.81). The appearance of N3481 was associated with a significant increase in viral load (p < 0.001), which was as large as the viral load increases observed for any of the TAMS. However, this analysis did not account for the simultaneous selection of other RT or protease inhibitor resistance mutations on viral load. To delineate the role of this mutation in RT inhibitor resistance, N3481 was introduced into HIV-1 molecular clones containing different genetic backbones. N3481 decreased zidovudine susceptibility 2-to 4-fold in the context of wildtype HIV-1 or when combined with TAMS. N3481 also decreased susceptibility to nevirapine (7.4fold) and efavirenz (2.5-fold) and significantly potentiated resistance to these drugs when combined with K103N. Biochemical analyses of recombinant RT containing N3481 provide supporting evidence for the role of this mutation in zidovudine and NNRTI resistance and give some insight into the molecular mechanism of resistance. Conclusions This study provides the first in vivo evidence that treatment with RT inhibitors can select a mutation (i.e., N3481) outside the polymerase domain of the HIV-1 RT that confers dual-class resistance. Its emergence, which can happen early during therapy, may significantly impact on a patient's response to antiretroviral therapies containing zidovudine and nevirapine. This study also provides compelling evidence for investigating the role of other mutations in the connection and RNase H domains in virological failure., Introduction The advent of highly active antiretroviral therapy has dramatically improved the clinical status of many HIVinfected patients. However, one of the major contributing factors to virological failure during highly [...]

Abstract: Its toroidal structure allows the proliferating cell nuclear antigen (PCNA) to wrap around and move along the DNA fiber, thereby dramatically increasing the processivity of DNA polymerization. PCNA is [...]

Author(s): Victor Serebrov [1]; Anna Marie Pyle (corresponding author) [1, 2] The NS3 helicase is essential for cytoplasmic RNA replication by the hepatitis C virus [1, 2, 3, 4], and [...]

Key Words translesion polymerase, somatic hypermutation, untargeted mutagenesis, nonhomologous end joining, polymerase recruitment Abstract Cells have high-fidelity polymerases whose task is to accurately replicate the genome, and low-fidelity polymerases with [...]

Introduction: Human immunodeficiency virus (HIV) type‐1 non‐nucleoside and nucleoside reverse transcriptase inhibitors (NNRTIs) are key drugs of highly active antiretroviral therapy (HAART) in the clinical management of acquired immune deficiency syndrome (AIDS)/HIV infection. Discussion: First‐generation NNRTIs, nevirapine (NVP), delavirdine (DLV) and efavirenz (EFV) are drugs with a low genetic barrier and poor resistance profile, which has led to the development of new generations of NNRTIs. Second‐generation NNRTIs, etravirine (ETR) and rilpivirine (RPV) have been approved by the Food and Drug Administration and European Union, and the next generation of drugs is currently being clinically developed. This review describes recent clinical data, pharmacokinetics, metabolism, pharmacodynamics, safety and tolerability of commercialized NNRTIs, including the effects of sex, race and age differences on pharmacokinetics and safety. Moreover, it summarizes the characteristics of next‐generation NNRTIs: lersivirine, GSK 2248761, RDEA806, BILR 355 BS, calanolide A, MK‐4965, MK‐1439 and MK‐6186. Conclusions: This review presents a wide description of NNRTIs, providing useful information for researchers interested in this field, both in clinical use and in research., Introduction Infections with the human immunodeficiency virus (HIV) are typically treated with drug combinations consisting of at least three different antiretroviral drugs. Essential components of this highly active antiretroviral therapy [...]

Introduction: Human immunodeficiency virus (HIV) type-1 non-nucleoside and nucleoside reverse transcriptase inhibitors (NNRTIs) are key drugs of highly active antiretroviral therapy (HAART) in the clinical management of acquired immune deficiency syndrome (AIDS)/HIV infection. Discussion: First-generation NNRTIs, nevirapine (NVP), delavirdine (DLV) and efavirenz (EFV) are drugs with a low genetic barrier and poor resistance profile, which has led to the development of new generations of NNRTIs. Second-generation NNRTIs, etravirine (ETR) and rilpivirine (RPV) have been approved by the Food and Drug Administration and European Union, and the next generation of drugs is currently being clinically developed. This review describes recent clinical data, pharmacokinetics, metabolism, pharmacodynamics, safety and tolerability of commercialized NNRTIs, including the effects of sex, race and age differences on pharmacokinetics and safety. Moreover, it summarizes the characteristics of next-generation NNRTIs: lersivirine, GSK 2248761, RDEA806, BILR 355 BS, calanolide A, MK-4965, MK-1439 and MK-6186. Conclusions: This review presents a wide description of NNRTIs, providing useful information for researchers interested in this field, both in clinical use and in research. Keywords: human immunodeficiency virus; non-nucleoside reverse transcriptase inhibitors; nevirapine; delavirdine; efavirenz; etravirine; rilpivirine; next-generation non-nucleoside reverse transcriptase inhibitors., Introduction Infections with the human immunodeficiency virus (HIV) are typically treated with drug combinations consisting of at least three different antiretroviral drugs. Essential components of this highly active antiretroviral therapy [...]

Author(s): Giovanni Maga (corresponding author) [1, 4]; Giuseppe Villani [2]; Emmanuele Crespan [1]; Ursula Wimmer [4]; Elena Ferrari [4]; Barbara Bertocci [3]; Ulrich Hübscher [4] Specialized DNA polymerases (DNA pols) [...]

Author(s): Courtney Prochnow [1, 2]; Ronda Bransteitter [1, 2]; Michael G. Klein [1]; Myron F. Goodman [1]; Xiaojiang S. Chen (corresponding author) [1] APOBEC-2 (APO2) belongs to the family of [...]

Integrase (IN)mediates the covalent insertion of the retroviral genome into its host chromosomal DNA. This enzymatic activity can be reconstituted in vitro with short DNA oligonucleotides, which mimic a single [...]

During the first half of the twentieth century, biochemists pondered the identity of genetic material with great wonderment. How can biological material replicate itself? This question was answered, in principle, [...]