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Summary: Precise double-strand break (DSB) repair is a paramount for genome stability. Homologous recombination (HR) repairs DSBs when cyclin-dependent kinase (CDK) activity is high, which correlates with the availability of the sister chromatid as a template. However, anaphase and telophase are paradoxical scenarios since high CDK favors HR despite sister chromatids being no longer aligned. To identify factors specifically involved in DSB repair in late mitosis, we have undertaken comparative proteomics in Saccharomyces cerevisiae and found that meiotic sister chromatid 1 (Msc1), a poorly characterized nuclear envelope protein, is significantly enriched upon both random and guided DSBs. We further show that Δmsc1 is more sensitive to DSBs in late mitosis, and has a delayed repair of DBSs, as indicated by increased Rad53 hyperphosphorylation, a higher presence of RPA foci, fewer Rad52 repair factories, and slower HR completion. We propose that Msc1 favors the later stages of HR and the timely completion of DSB repair before cytokinesis.

The morphology of the nucleus is roughly spherical in most eukaryotic cells. However, this organelle shape needs to change as the cell travels through narrow intercellular spaces during cell migration and during cell division in organisms that undergo closed mitosis, i.e., without dismantling the nuclear envelope, such as yeast. In addition, the nuclear morphology is often modified under stress and in pathological conditions, being a hallmark of cancer and senescent cells. Thus, understanding nuclear morphological dynamics is of uttermost importance, as pathways and proteins involved in nuclear shaping can be targeted in anticancer, antiaging, and antifungal therapies. Here, we review how and why the nuclear shape changes during mitotic blocks in yeast, introducing novel data that associate these changes with both the nucleolus and the vacuole. Altogether, these findings suggest a close relationship between the nucleolar domain of the nucleus and the autophagic organelle, which we also discuss here. Encouragingly, recent evidence in tumor cell lines has linked aberrant nuclear morphology to defects in lysosomal function.

Abstract The key role of Topoisomerase II (Top2) is the removal of topological intertwines between sister chromatids. In yeast, inactivation of Top2 brings about distinct cell cycle responses. In the case of the conditional top2-5 allele, interphase and mitosis progress on schedule but cells suffer from a chromosome segregation catastrophe. We here show that top2-5 chromosomes fail to enter a Pulsed-Field Gel Electrophoresis (PFGE) in the first cell cycle, a behavior traditionally linked to the presence of replication and recombination intermediates. We distinguished two classes of affected chromosomes: the rDNA-bearing chromosome XII, which fails to enter a PFGE at the beginning of S-phase, and all the other chromosomes, which fail at a postreplicative stage. In synchronously cycling cells, this late PFGE retention is observed in anaphase; however, we demonstrate that this behavior is independent of cytokinesis, stabilization of anaphase bridges, spindle pulling forces and, probably, anaphase onset. Strikingly, once the PFGE retention has occurred it becomes refractory to Top2 re-activation. DNA combing, two-dimensional electrophoresis, genetic analyses, and GFP-tagged DNA damage markers suggest that neither recombination intermediates nor unfinished replication account for the postreplicative PFGE shift, which is further supported by the fact that the shift does not trigger the G2/M checkpoint. We propose that the absence of Top2 activity leads to a general chromosome structural/topological change in mitosis.

The mechanism regulating DNA repair in late anaphase or telophase is not yet clear. Here authors reveal that DNA double strand breaks in telophase causes a partial reversal of sister chromosome segregation which could create an opportunity of using the sister for repair in telophase.

Topoisomerase II (Top2) is an essential protein that resolves DNA catenations. When Top2 is inactivated, mitotic catastrophe results from massive entanglement of chromosomes. Top2 is also the target of many first-line anticancer drugs, the so-called Top2 poisons. Often, tumors become resistant to these drugs by acquiring hypomorphic mutations in the genes encoding Top2. Here, we have compared the cell cycle and nuclear segregation of two coisogenic Saccharomyces cerevisiae strains carrying top2 thermosensitive alleles that differ in their resistance to Top2 poisons: the broadly-used poison-sensitive top2-4 and the poison-resistant top2-5. Furthermore, we have performed genome-scale synthetic genetic array (SGA) analyses for both alleles under permissive conditions, chronic sublethal Top2 downregulation, and acute, yet transient, Top2 inactivation. We find that slowing down mitotic progression, especially at the time of execution of the mitotic exit network (MEN), protects against Top2 deficiency. In all conditions, genetic protection was stronger in top2-5; this correlated with cell biology experiments in this mutant, whereby we observed destabilization of both chromatin and ultrafine anaphase bridges by execution of MEN and cytokinesis. Interestingly, whereas transient inactivation of the critical MEN driver Cdc15 partly suppressed top2-5 lethality, this was not the case when earlier steps within anaphase were disrupted; i.e., top2-5 cdc14-1. We discuss the basis of this difference and suggest that accelerated progression through mitosis may be a therapeutic strategy to hypersensitize cancer cells carrying hypomorphic mutations in TOP2.

DNA repair in late mitosis sets paradoxical scenarios. Cyclin-dependent kinase (CDK) activity is high, which favors homologous recombination (HR), despite a sister chromatid is not physically close to recombine with. We have found that DNA double-strand breaks partially revert chromosome segregation to find an intact template and repair through HR.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Synopsis Background Direct myocardial cell protection in patients with unstable angina or evolving myocardial infarction (MI) could prevent cell necrosis or reduce its extent, and minimize the risk of MI and death associated with percutaneous coronary interventions (PCIs) and coronary artery bypass surgery. The myocardial NHE plays a critical role in mediating the progression of ischemia to necrosis by promoting intracellular accumulation of sodium and calcium in exchange for hydrogen. Blockage of the system in various experimental models of ischemia and reperfusion had a strong antinecrotic effect. The present paper describes a trial that was intended to investigate the potential clinical benefit of cariporide, a potent and selective inhibitor of the NHE, in a large spectrum of at-risk patients. Trial design The GUARDIAN trial was a multicenter, double-blind, randomized, four-arm trial that compared three cariporide dosages with placebo in patients with unstable angina and non-ST-segment elevation myocardial infarction (UA/NSTEMI) and in patients undergoing a high-risk PCI or coronary artery bypass surgery. A total of 11 590 patients with one of the three possible entry diagnoses were enroled in 23 countries. The trial was designed as a combined phase 2/phase 3 study. The primary objective was to evaluate the efficacy of cariporide in reducing all-cause mortality and/or MI across the various entry populations 36 days after randomization. Three different doses of cariporide were compared with placebo. Secondary end-points were death or non-fatal MI at 10 days and 6 months, and cardiac events related to left ventricular dysfunction. The extent of MI was also assessed by peak elevation in creatinine kinase (CK)-MB and a ratio of peak elevation to normal values. The sample size was driven by a total event rate of 1200 patients experiencing a primary end-point, powered to detect a 25% risk reduction in any of the three treatment groups compared with placebo at a significance level of 0.02, accounting for the three pair wise comparisons.

Noncompliance with adult instruction is a common problem exhibited by individuals diagnosed with intellectual and developmental disabilities. The high-probability (high-p) request sequence was designed to increase compliance with low-probability (low-p) instructions by rapidly presenting high-p instructions immediately prior to the targeted low-p instruction. This study evaluated the use of three different levels of the high-p request sequence (i.e., one instruction, three instructions, and six instructions) to increase the compliance of five children who were diagnosed with autism spectrum disorder (ASD). Results indicated that all three levels of the high-p request sequence were often successful in increasing compliance with low-p instructions; however, when given the opportunity to choose, participants and caregivers (i.e., mothers and therapists) tended to prefer the high-p request sequence with three instructions.

Procedural arrangements of differential reinforcement of alternative behavior without extinction often involve presenting the same reinforcers for problem behavior and appropriate behavior, which is typically ineffective at reducing problem behavior and increasing an alternative response. However, manipulating reinforcement dimensions such that the contingencies favor the alternative response may improve treatment outcomes when using differential reinforcement of alternative behavior without extinction by increasing appropriate behavior and reducing problem behavior. We conducted this translational study with 32 college students completing a button-pressing task on a computer program in which they could engage in analogs to problem behavior and appropriate behavior. The effects of manipulating magnitude, immediacy, quality, and a combination of all three dimensions for the alternative response were evaluated. Overall, all dimension manipulations reduced the analog to problem behavior, with the largest reductions observed during the quality probe and the probe with all dimensions combined. These results support the notion that differential reinforcement of alternative behavior without extinction can be an effective form of treatment.

Behavioral assessment allows a clinician to identify environmental events that are contributing to challenging behavior to inform effective treatment. Recent developments in behavioral assessment and treatment have been devoted to creating practical procedures that can be conducted by clinicians in socially relevant settings. However, the extent to which these procedural modifications affect treatment outcomes has yet to be fully explored. We conducted a consecutive case series with 13 individuals admitted to an outpatient program to address their challenging behavior. The patients experienced a behavioral package conducted in three phases (practical functional assessment [PFA], behavioral treatment, extension). Results demonstrated near elimination of challenging behavior for all patients after extending the treatment to include denials to reinforcement and instructions to complete other tasks.

Functional communication training, an intervention for challenging behavior rooted in principles of applied behavior analysis, has copious empirical support dating back to the mid-1980s for autistic individuals. Recently, there has been a concerted effort to thin reinforcement delivery during functional communication training using contingency-based delays that, in turn, are designed to enhance practicality and feasibility while not compromising on efficacy. In this synthesis, we meta-analyzed the literature using log response ratio effect sizes to investigate (a) combined and across type effectiveness of contingency-based delays and (b) moderating variables that might impact intervention outcomes. Findings showed that contingency-based delays were effective for autistic individuals (log response ratio = -2.17; 95% CI = (-2.76, -1.58)) and most effective when the contingency incorporated positive reinforcement (log response ratio = -2.30; 95% CI = (-2.83, -1.78)). In addition, delay procedures that included differential reinforcement of alternative behavior were overall more effective (log response ratio = -2.13; 95% CI = (-2.72, -1.55)) than those that involved differential reinforcement of other behavior (log response ratio = -1.24; 95% CI = (-3.84, 1.37)). Noteworthy moderating variables found to impact contingency-based delay efficacy included the intervention dosage and the topography of behavior. We discuss these findings and highlight directions where additional empirical research is warranted to improve our understanding about contingency-based delays for autistic individuals.

Jessel et al. ("Behavior Analysis & Practice," 13(1), 205-216, 2020a) conducted a review of the functional analysis literature between the years 1965 and 2016. The authors found an increasing trend in analyses replicating the components of Iwata et al. ("Journal of Applied Behavior Analysis," 27, 197-209, 1982/1994a) and determined that those components have come to represent a standard format. Since the inception of the standard, other functional analysis formats (e.g., brief, latency-based, trial-based) have been developed to improve analysis efficiency and control, with most retaining fundamental components of the standard and some omitting all (e.g., interview-informed, synthesized contingency analysis; IISCA). We conducted a review of functional analyses in this two-part evaluation to determine the levels of efficiency and control afforded by functional analysis variations and formats.

While much existing work on digital storytelling with young people has focused prominently upon presenting their own personal narratives and viewpoints, relatively little attention has been given to learning that could arise from digital adaptations by young children of existing and well-known stories. This article reports work exploring learning activities through a case study involving three pupils (aged 8, 10 and 12) and their teachers engaged over a 6-month period in digitally retelling a fairy tale from a printed storybook. In addition to considering the role of the printed text and the learning opportunities arising from its digital retelling, discussion focuses on how the findings cohere with more recently developing theoretical perspectives on learning that in addition to the social take into account the role of the material.