The 9-1-1 checkpoint clamp coordinates resection at DNA double strand breaks

DNA-end resection, the generation of single-stranded DNA at DNA double strand break (DSB) ends, is critical for controlling the many cellular responses to breaks. Here we show that the conserved DNA damage checkpoint sliding clamp (the 9-1-1 complex) plays two opposing roles coordinating DSB resection in budding yeast. We show that the major effect of 9-1-1 is to inhibit resection by promoting the recruitment of Rad953BP1 near DSBs. However, 9-1-1 also stimulates resection by Exo1- and Dna2-Sgs1-dependent nuclease/helicase activities, and this can be observed in the absence of Rad953BP1. Our new data resolve the controversy in the literature about the effect of the 9-1-1 complex on DSB resection. Interestingly, the inhibitory role of 9-1-1 on resection is not observed near uncapped telomeres because less Rad953BP1 is recruited near uncapped telomeres. Thus, 9-1-1 both stimulates and inhibits resection and the effects of 9-1-1 are modulated by different regions of the genome. Our experiments illustrate the central role of the 9-1-1 checkpoint sliding clamp in the DNA damage response network that coordinates the response to broken DNA ends. Our results have implications in all eukaryotic cells

The 9-1-1 checkpoint clamp stimulates DNA resection by Dna2-Sgs1 and Exo1

Single-stranded DNA (ssDNA) at DNA ends is an important regulator of the DNA damage response. Resection, the generation of ssDNA, affects DNA damage checkpoint activation, DNA repair pathway choice, ssDNA-associated mutation and replication fork stability. In eukaryotes, extensive DNA resection requires the nuclease Exo1 and nuclease/helicase pair: Dna2 and Sgs1^(BLM). How Exo1 and Dna2-Sgs1^(BLM) coordinate during resection remains poorly understood. The DNA damage checkpoint clamp (the 9-1-1 complex) has been reported to play an important role in stimulating resection but the exact mechanism remains unclear. Here we show that the human 9-1-1 complex enhances the cleavage of DNA by both DNA2 and EXO1 in vitro, showing that the resection-stimulatory role of the 9-1-1 complex is direct. We also show that in Saccharomyces cerevisiae, the 9-1-1 complex promotes both Dna2-Sgs1 and Exo1-dependent resection in response to uncapped telomeres. Our results suggest that the 9-1-1 complex facilitates resection by recruiting both Dna2-Sgs1 and Exo1 to sites of resection. This activity of the 9-1-1 complex in supporting resection is strongly inhibited by the checkpoint adaptor Rad9^(53BP1). Our results provide important mechanistic insights into how DNA resection is regulated by checkpoint proteins and have implications for genome stability in eukaryotes

Systematic analysis of the DNA damage response network in telomere defective budding yeast

Functional telomeres are critically important to eukaryotic genetic stability. Scores of proteins and pathways are known to affect telomere function. Here, we report a series of related genome-wide genetic interaction screens performed on budding yeast cells with acute or chronic telomere defects. Genetic interactions were examined in cells defective in Cdc13 and Stn1, affecting two components of CST, a single stranded DNA (ssDNA) binding complex that binds telomeric DNA. For comparison, genetic interactions were also examined in cells with defects in Rfa3, affecting the major ssDNA binding protein, RPA, which has overlapping functions with CST at telomeres. In more complex experiments, genetic interactions were measured in cells lacking EXO1 or RAD9, affecting different aspects of the DNA damage response, and containing a cdc13-1 induced telomere defect. Comparing fitness profiles across these data sets helps build a picture of the specific responses to different types of dysfunctional telomeres. The experiments show that each context reveals different genetic interactions, consistent with the idea that each genetic defect causes distinct molecular defects. To help others engage with the large volumes of data, the data are made available via two interactive web-based tools: Profilyzer and DIXY. One particularly striking genetic interaction observed was that the chk1∆ mutation improved fitness of cdc13-1 exo1∆ cells more than other checkpoint mutations (ddc1∆, rad9∆, rad17∆, and rad24∆), whereas, in cdc13-1 cells, the effects of all checkpoint mutations were similar. We show that this can be explained by Chk1 stimulating resection—a new function for Chk1 in the eukaryotic DNA damage response network

EXPERIENCE OF PSYCHIATRY TEACHING AT MEDICAL SCHOOL INFLUENCES CROATIAN MEDICAL STUDENTS’ ATTITUDES TOWARDS CHOOSING PSYCHIATRY AS A CAREER

Background: Reports indicate that the number of students interested in choosing psychiatry as their future profession is constantly decreasing in the last decades. Our aim was to determine the proportion of medical students intending to pursue a career in psychiatry and to define undergraduate education-related factors influencing that choice. Subjects and methods: We report the preliminary findings of a cross sectional quantitative survey of final year Croatian medical students as part of the International Survey Of Student Career Choice In Psychiatry (ISOSCCIP). We surveyed medical students attending their final year at Zagreb School of Medicine in the academic year 2009/2010, using a structured questionnaire examining demographics, students\u27 preferences on future career choice and their evaluations of undergraduate psychiatry teaching. Results: The overall student evaluation of the compulsory psychiatry curriculum was “average”. Significantly higher ratings were reported by students who felt more involved in the teaching of the subject. The possibility of psychiatry as a career choice correlated significantly with better evaluation grades of psychiatry lectures. Furthermore, poor evaluation grades predicted a higher likelihood that medical students completely ruled out choosing a career in psychiatry. Conclusion: This is the first survey of this kind in Croatia. Student ratings of medical school psychiatric education and perceived involvement in teaching appears to influence the likelihood of a stated career in psychiatry. Addressing these issues may increase the number of students motivated to pursue psychiatry as their future career choice

EXPERIENCE OF PSYCHIATRY TEACHING AT MEDICAL SCHOOL INFLUENCES CROATIAN MEDICAL STUDENTS’ ATTITUDES TOWARDS CHOOSING PSYCHIATRY AS A CAREER

Background: Reports indicate that the number of students interested in choosing psychiatry as their future profession is constantly decreasing in the last decades. Our aim was to determine the proportion of medical students intending to pursue a career in psychiatry and to define undergraduate education-related factors influencing that choice. Subjects and methods: We report the preliminary findings of a cross sectional quantitative survey of final year Croatian medical students as part of the International Survey Of Student Career Choice In Psychiatry (ISOSCCIP). We surveyed medical students attending their final year at Zagreb School of Medicine in the academic year 2009/2010, using a structured questionnaire examining demographics, students\u27 preferences on future career choice and their evaluations of undergraduate psychiatry teaching. Results: The overall student evaluation of the compulsory psychiatry curriculum was “average”. Significantly higher ratings were reported by students who felt more involved in the teaching of the subject. The possibility of psychiatry as a career choice correlated significantly with better evaluation grades of psychiatry lectures. Furthermore, poor evaluation grades predicted a higher likelihood that medical students completely ruled out choosing a career in psychiatry. Conclusion: This is the first survey of this kind in Croatia. Student ratings of medical school psychiatric education and perceived involvement in teaching appears to influence the likelihood of a stated career in psychiatry. Addressing these issues may increase the number of students motivated to pursue psychiatry as their future career choice

Genetic association of the tachykinin receptor 1 TACR1 gene in bipolar disorder, attention deficit hyperactivity disorder, and the alcohol dependence syndrome

Single nucleotide polymorphisms (SNPs) in the tachykinin receptor 1 gene (TACR1) are nominally associated with bipolar affective disorder (BPAD) in a genome-wide association study and in several case-control samples of BPAD, alcohol dependence syndrome (ADS) and attention-deficit hyperactivity disorder (ADHD). Eighteen TACR1 SNPs were associated with BPAD in a sample (506 subjects) from University College London (UCL1), the most significant being rs3771829, previously associated with ADHD. To further elucidate the role of TACR1 in affective disorders, rs3771829 was genotyped in a second BPAD sample of 593 subjects (UCL2), in 997 subjects with ADS, and a subsample of 143 individuals diagnosed with BPAD and comorbid alcohol dependence (BPALC). rs3771829 was associated with BPAD (UCL1 and UCL2 combined: P = 2.0 × 10(-3) ), ADS (P = 2.0 × 10(-3) ) and BPALC (P = 6.0 × 10(-4) ) compared with controls screened for the absence of mental illness and alcohol dependence. DNA sequencing in selected cases of BPAD and ADHD who had inherited TACR1-susceptibility haplotypes identified 19 SNPs in the promoter region, 5' UTR, exons, intron/exon junctions and 3' UTR of TACR1 that could increase vulnerability to BPAD, ADS, ADHD, and BPALC. Alternative splicing of TACR1 excludes intron 4 and exon 5, giving rise to two variants of the neurokinin 1 receptor (NK1R) that differ in binding affinity of substance P by 10-fold. A mutation in intron four, rs1106854, was associated with BPAD, although a regulatory role for rs1106854 is unclear. The association with TACR1 and BPAD, ADS, and ADHD suggests a shared molecular pathophysiology between these affective disorders. © 2014 The Authors. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics Published by Wiley Periodicals

Choice of antipsychotic treatment by European psychiatry trainees: are decisions based on evidence?

Background: Little is known about the factors influencing treatment choice in psychosis, the majority of this work being conducted with specialists (consultant) in psychiatry. We sought to examine trainees' choices of treatment for psychosis if they had to prescribe it for themselves, their patients, and factors influencing decision-making. Methods: Cross-sectional, semi-structured questionnaire-based study. Results: Of the 726 respondents (response rate = 66%), the majority chose second-generation antipsychotics (SGAs) if they had to prescribe it for themselves (n = 530, 93%) or for their patients (n = 546, 94%). The main factor influencing choice was perceived efficacy, 84.8% (n = 475) of trainees stating this was the most important factor for the patient, and 77.8% (n = 404) stating this was the most important factor for their own treatment. Trainees with knowledge of trials questioning use of SGAs (CATIE, CUtLASS, TEOSS) were more likely to choose second-generation antipsychotics than those without knowledge of these trials (chi(2) = 3.943; p = 0.047; O.R. = 2.11; 95% C.I. = 1.0-4.48). Regarding psychotherapy, cognitive behavioural therapy (CBT) was the most popular choice for self (33.1%; n = 240) and patient (30.9%; n = 224). Trainees were significantly more likely to prefer some form of psychotherapy for themselves rather than patients (chi(2) = 9.98; p < 0,002; O.R. = 1.54; 95% CIs = 1.18-2.0). Conclusions: Trainees are more likely to choose second-generation antipsychotic medication for patients and themselves. Despite being aware of evidence that suggests otherwise, they predominantly base these choices on perceived efficacy

The 9-1-1 checkpoint clamp coordinates resection at DNA double strand breaks

DNA-end resection, the generation of single-stranded DNA at DNA double strand break (DSB) ends, is critical for controlling the many cellular re-sponses to breaks. Here we show that the conserved DNA damage checkpoint sliding clamp (the 9-1-1 complex) plays two opposing roles coordinating DSB resection in budding yeast. We show that the major effect of 9-1-1 is to inhibit resection by promoting the recruitment of Rad953BP1 near DSBs. However, 9-1-1 also stimulates resection by Exo1- and Dna2-Sgs1-dependent nuclease/helicase activities, and this can be observed in the absence of Rad953BP1. Our new data resolve the controversy in the literature about the effect of the 9-1-1 complex on DSB resection. In-terestingly, the inhibitory role of 9-1-1 on resection is not observed near uncapped telomeres because less Rad953BP1 is recruited near uncapped telomeres. Thus, 9-1-1 both stimulates and inhibits resection and the effects of 9-1-1 are modulated by different re-gions of the genome. Our experiments illustrate the central role of the 9-1-1 checkpoint sliding clamp in the DNA damage response network that coordinates the response to broken DNA ends. Our results have implications in all eukaryotic cells