The effect of some polymorphisms in vitamin D receptor gene in menopausal women with osteoporosis

Introduction: Vitamin D receptor gene is one of candidate genes related to osteoporosis expansion. The association of ApaI, TaqI, and BsmI polymorphisms in vitamin D receptor gene with bone metabolism and density has been already demonstrated. Aim: This study was conducted to investigate the association between the ApaI, TaqI and BsmI polymorphisms and bone density. This study was descriptive-analytical study. Centers for bone density measurement in southwestern Iran. Materials and Methods: In this descriptive-analytical study, 200 participants aged 45- and above 45-year-old women referring the centers of bone density measurement participated. The bone density of femoral neck and lumbar vertebrae was measured using dual-energy X-ray absorptiometry method. Based on t-score, the participants were assigned into patients (n=130) and healthy individuals (n=70). Different genotypes of ApaI (AA/Aa/aa), TaqI (TT/Tt/tt), and BsmI (BB/Bb/bb) were determined by PCR-RFLP. The data on bone density and PCR-RFLP were analysed by chi-square and ANOVA. Also, triad combination of the genotypes was statistically analysed. For each genotype combination, chi-square was run between the patients and control group and p-value was calculated. Results: No significant association was seen between ApaI polymorphism and bone density (p>0.05). TaqI and BsmI polymorphisms had a significant association with femoral neck’s bone density (p0.05). Patients with homozygous dominant TT genotype had the least bone density in femoral neck compared to other genotypes. Lumbar vertebrae’s bone density was similar in three TaqI genotypes. The patients with homozygous recessive bb genotype had the least bone density in femoral neck and lumbar vertebrae compared to other genotypes. Conclusion: TaqI and BsmI polymorphisms could be desirable markers in diagnosis of women at risk of osteoporosis in the studied region in Iran. Therefore, these women will receive suitable medical treatment at proper tim

Calcitonin receptor AluI (rs1801197) and TaqI calcitonin genes polymorphism in 45-and over 45-year-old women and their association with bone density

Purpose: Calcitonin receptor gene has also a polymorphism which is associated with bone mass density. This study evaluates the association between calcitonin receptor AluI (rs1801197) and Taq1 calcitonin genes polymorphism with bone density rate. Methods: In this descriptive-analytical study in 2013 in southwestern Iran, 200 blood samples, per the Cochran sample size formula, were taken from women aged 45 and older. DNA was extracted from the samples using the phenol- chloroform method and the genomic fragments in question were proliferated using the polymerase chain reaction (PCR) method. Results: The genotypic distribution of polymorphism AluI for TT, TC, and CC genotypes in control group was 31.4%, 38.6%, and 30% and in patients 25.4%, 55.4%, and 19.2%, respectively. There was no significant difference in polymorphism AluI between patients and control group and no significant association was found between this gene and bone density rate (P > 0.05). All patients and the individuals in the control group exhibited tt genotype for TaqI calcitonin gene and no significant association was found between these participants and osteoporosis. Conclusion: There was no association between two polymorphisms and osteoporosis, and between polymorphism of these two genes and osteoporosis development rate in the participants. © 2016 Morteza Dehghan, Razieh Pourahmad-Jaktaji, and Zarghampoor Farzaneh

Investigation of mutations in exons 19-23 MYH7 gene in hypertrophic cardiomyopathy patients using PCR-SSCP/HA technique in Chaharmahal va Bakhtiari province

زمینه و هدف: کاردیومایوپاتی هایپرتروفی (HCM) رایج ترین نوع از بیماری های قلبی است که 2/0 درصد از جمعیت جهان را تحت تأثیر قرار داده و همچنین رایج ترین علت مرگ قلبی ناگهانی در جوانان زیر 35 سال است. حدود 35 درصد موارد بیماری مربوط به اگزون های 24- 8 از ژن MYH7 است. هدف این مطالعه بررسی احتمال حضور جهش های مربوط به ژن MYH7 در اگزون های 23-19 در بیماران HCM استان چهارمحال و بختیاری بود. روش بررسی: در این مطالعه تجربی 30 بیمار مبتلا به HCM به روش نمونه گیری آسان از بین مراجعین به کلینیک قلب دانشگاه علوم پزشکی شهرکرد انتخاب شدند. در این بیماران DNAبه روش استاندارد فنل-کلروفرم استخراج شد. اگزون های مورد نظر با استفاده از روش PCR تکثیر و با روش SSCP به صورت تک رشته تبدیل شد و همراه نمونه های دو رشته ای روی ژل پلی آکریل آمید الکتروفورز گردید. سپس باندهای مشکوک تعیین توالی گردید و نتایج با استفاده از نرم افزار Chromas تجزیه و تحلیل شدند. یافته ها: در اگزون های 20، 21 و 23 تغییری مشاهده نشد، اما در اگزون های 19 و 22 دو جهش R719W و R870H یافت شد که به ترتیب در دو و یک نفر از بیماران وجود داشتند. نتیجه گیری: از آنجا که تغییرات در اگزون های 19 و 22 باعث تغییر اسید آمینه ای در میوزین بتا می شود، جهش‌های ژن MYH7 در این اگزون ها، احتمالاً سهم به سزایی در بیماران HCM این استان دارند. به هر صورت، لازم است برای نتیجه گیری بهتر، بیماران بیشتری مورد مطالعه قرار گیرند

Cellular location and activity of Escherichia coli RecG proteins shed light on the function of its structurally unresolved C-terminus

RecG is a DNA translocase encoded by most species of bacteria. The Escherichia coli protein targets branched DNA substrates and drives the unwinding and rewinding of DNA strands. Its ability to remodel replication forks and to genetically interact with PriA protein have led to the idea that it plays an important role in securing faithful genome duplication. Here we report that RecG co-localises with sites of DNA replication and identify conserved arginine and tryptophan residues near its C-terminus that are needed for this localisation. We establish that the extreme C-terminus, which is not resolved in the crystal structure, is vital for DNA unwinding but not for DNA binding. Substituting an alanine for a highly conserved tyrosine near the very end results in a substantial reduction in the ability to unwind replication fork and Holliday junction structures but has no effect on substrate affinity. Deleting or substituting the terminal alanine causes an even greater reduction in unwinding activity, which is somewhat surprising as this residue is not uniformly present in closely related RecG proteins. More significantly, the extreme C-terminal mutations have little effect on localisation. Mutations that do prevent localisation result in only a slight reduction in the capacity for DNA repair. © 2014 The Author(s)

Pathological replication in cells lacking RecG DNA translocase

Little is known about what happens when forks meet to complete DNA replication in any organism. In this study we present data suggesting that the collision of replication forks is a potential threat to genomic stability. We demonstrate that Escherichia coli cells lacking RecG helicase suffer major defects in chromosome replication following UV irradiation, and that this is associated with high levels of DNA synthesis initiated independently of the initiator protein DnaA. This UV-induced stable DNA replication is dependent on PriA helicase and continues long after UV-induced lesions have been excised. We suggest UV irradiation triggers the assembly of new replication forks, leading to multiple fork collisions outside the terminus area. Such collisions may generate branched DNAs that serve to establish further new forks, resulting in uncontrolled DNA amplification. We propose that RecG reduces the likelihood of this pathological cascade being set in motion by reducing initiation of replication at D- and R-loops, and other structures generated as a result of fork collisions. Our results shed light on why replication initiation in bacteria is limited to a single origin and why termination is carefully orchestrated to a single event within a restricted area each cell cycle

Replication fork collisions cause pathological chromosomal amplification in cells lacking RecG DNA translocase

Duplication and transmission of chromosomes require precise control of chromosome replication and segregation. Here we present evidence that RecG is a major factor influencing these processes in bacteria. We show that the extensive DnaA-independent stable DNA replication observed without RecG can lead to replication of any area of the chromosome. This replication is further elevated following irradiation with UV light and appears to be perpetuated by secondary events that continue long after the elimination of UV lesions. The resulting pathological cascade is associated with an increased number of replication forks traversing the chromosome, sometimes with extensive regional amplification of the chromosome, and with the accumulation of highly branched DNA intermediates containing few Holliday junctions. We propose that the cascade is triggered by replication fork collisions that generate 3′ single-strand DNA flaps, providing sites for PriA to initiate re-replication of the DNA and thus to generate linear duplexes that provoke recombination, allowing priming of even further replication. Our results shed light on why termination of replication in bacteria is normally limited to a single encounter of two forks and carefully orchestrated within a restricted area, and explain how a system of multiple forks and random termination can operate in eukaryotes

RecG interacts directly with SSB: implications for stalled replication fork regression

RecG and RuvAB are proposed to act at stalled DNA replication forks to facilitate replication restart. To define the roles of these proteins in fork regression, we used a combination of assays to determine whether RecG, RuvAB or both are capable of acting at a stalled fork. The results show that RecG binds to the C-terminus of single-stranded DNA binding protein (SSB) forming a stoichiometric complex of 2 RecG monomers per SSB tetramer. This binding occurs in solution and to SSB protein bound to single stranded DNA (ssDNA). The result of this binding is stabilization of the interaction of RecG with ssDNA. In contrast, RuvAB does not bind to SSB. Side-by-side analysis of the catalytic efficiency of the ATPase activity of each enzyme revealed that (−)scDNA and ssDNA are potent stimulators of the ATPase activity of RecG but not for RuvAB, whereas relaxed circular DNA is a poor cofactor for RecG but an excellent one for RuvAB. Collectively, these data suggest that the timing of repair protein access to the DNA at stalled forks is determined by the nature of the DNA available at the fork. We propose that RecG acts first, with RuvAB acting either after RecG or in a separate pathway following protein-independent fork regression

RecG directs DNA synthesis during double-strand break repair

Homologous recombination provides a mechanism of DNA double-strand break repair (DSBR) that requires an intact, homologous template for DNA synthesis. When DNA synthesis associated with DSBR is convergent, the broken DNA strands are replaced and repair is accurate. However, if divergent DNA synthesis is established, over-replication of flanking DNA may occur with deleterious consequences. The RecG protein of Escherichia coli is a helicase and translocase that can re-model 3-way and 4-way DNA structures such as replication forks and Holliday junctions. However, the primary role of RecG in live cells has remained elusive. Here we show that, in the absence of RecG, attempted DSBR is accompanied by divergent DNA replication at the site of an induced chromosomal DNA double-strand break. Furthermore, DNA double-stand ends are generated in a recG mutant at sites known to block replication forks. These double-strand ends, also trigger DSBR and the divergent DNA replication characteristic of this mutant, which can explain over-replication of the terminus region of the chromosome. The loss of DNA associated with unwinding joint molecules previously observed in the absence of RuvAB and RecG, is suppressed by a helicase deficient PriA mutation (priA300), arguing that the action of RecG ensures that PriA is bound correctly on D-loops to direct DNA replication rather than to unwind joint molecules. This has led us to put forward a revised model of homologous recombination in which the re-modelling of branched intermediates by RecG plays a fundamental role in directing DNA synthesis and thus maintaining genomic stability