The role of cohesion fatigue in chromosome instability

描述（由申请人提供）：染色体不稳定性（CIN）是包括癌症、出生缺陷和不孕症在内的几种人类健康问题的重要组成部分。Gorbsky实验室发现了一种新的CIN来源，称为内聚疲劳。内聚疲劳是细胞中姐妹染色单体在中期延迟分离的进行性异步分离。本项目的总体目标是绘制内聚疲劳的下游后果，染色单体交出内聚的机制，以及调节细胞对内聚疲劳敏感性的上游途径。在目标1中，将使用单细胞水平和群体水平的先进显微镜来跟踪由内聚疲劳引起的染色体异常。内聚疲劳有可能同时产生两种类型的总染色体畸变，这两种类型的总染色体畸变通常发生在肿瘤发生期间，即全染色体数目的变化（非整倍性）和大片段染色体复制、缺失和易位。此外，内聚疲劳极有可能导致微核的形成，这被认为是大量DNA损伤的位点。目的2将通过实验确定内聚疲劳过程中内聚蛋白释放的机制，这些实验锁定了内聚蛋白复合物的各个关节。此外，定量质谱法将用于分析在内聚疲劳期间在其翻译后修饰中被去除或改变的内聚蛋白组分。目标3将绘制调节内聚疲劳敏感性的上游途径，集中于可能加剧CIN的转化细胞中的缺陷。转化的细胞通常表现出细胞周期调节因子的缺陷，而凝聚基因是人类肿瘤中最常见的突变基因之一。因此，转化的细胞可能对内聚疲劳高度敏感。这一目标将测试细胞周期调节因子的改变如何诱导中期延迟，以及这些延迟如何与纺锤体微管动力学和染色体凝聚力中的转化相关缺陷协同作用，以促进凝聚力疲劳。目的4将内聚疲劳的分析扩展到芽殖酵母，以检查内聚疲劳调节因子在有丝分裂中的保守性，并测试有关内聚疲劳如何导致减数分裂期间同源染色体之间的内聚过早丧失的具体假设。最近的证据表明，染色体凝聚力的衰减是母体年龄效应的一个因素，因此老年妇女的卵母细胞显示出非整倍体的发生率大大增加。在哺乳动物配子中，内聚疲劳可能是减数分裂非整倍体的一个重要原因，导致出生缺陷和不育。

DESCRIPTION (provided by applicant): Chromosome instability (CIN) is an important component in several human health problems including cancer, birth defects, and infertility. The Gorbsky lab discovered a new source of CIN that was termed cohesion fatigue. Cohesion fatigue is the progressive, asynchronous separation of sister chromatids in cells delayed at metaphase. The overall goals of this project are to map the downstream consequences of cohesion fatigue, the mechanisms by which chromatids surrender cohesion, and the upstream pathways that modulate the cell sensitivity to cohesion fatigue. In Aim 1, advanced microscopy at both the single cell level and population level will be used to track the chromosome abnormalities that arise from cohesion fatigue. Cohesion fatigue has the potential to simultaneously generate the two types of gross chromosome aberrations that often arise during oncogenesis, changes in whole chromosome number (aneuploidy) and large segmental chromosome duplications, deletions, and translocations. In addition, cohesion fatigue is highly likely to lead to the formation of micronuclei, which have been implicated as sites of massive DNA damage. Aim 2 will determine the mechanisms of cohesin release during cohesion fatigue through experiments that lock individual joints of the cohesin protein complex. In addition, quantitative mass spectrometry will be used to analyze cohesin components that are removed or altered in their post-translational modifications during cohesion fatigue. Aim 3 will map the upstream pathways that regulate sensitivity to cohesion fatigue, concentrating on defects in transformed cells that may exacerbate CIN. Transformed cells often exhibit defects in cell cycle regulators, and cohesion genes are among the most often mutated in human tumors. Thus, transformed cells may be highly susceptible to cohesion fatigue. This aim will test how alterations of cell cycle regulators induce metaphase delays and how these delays synergize with transformation-associated defects in spindle microtubule dynamics and chromosome cohesion to promote cohesion fatigue. Aim 4 extends the analysis of cohesion fatigue to budding yeast to examine the conservation of cohesion fatigue regulators in mitosis and to test specific hypotheses about how cohesion fatigue contributes to premature loss of cohesion between homologous chromosomes during meiosis. Recent evidence implicates decay in chromosome cohesion as a contributor to the maternal age effect, whereby the oocytes of older women show a greatly increased incidence of aneuploidy. In mammalian gametes, cohesion fatigue may be an important causative factor in meiotic aneuploidy, contributing to birth defects and infertility.