Chromosome instability resulting from double-strand breaks near telomeres

端粒附近双链断裂导致染色体不稳定

• 批准号: 7073078
• 负责人: John P. Murnane
• 金额: $ 26.45万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-06 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7073078
• 关键词: chromosomes; human; proteins; siblings; telomere; chromosomes; human; proteins; siblings; telomere

DESCRIPTION (provided by applicant): Exposure of mammalian cells to ionizing radiation is known to induce chromosome instability (CIN), which can promote the rapid accumulation of genetic changes leading to cancer. We have demonstrated that DSBs occurring near the ends of chromosomes, called telomeres, can promote CIN by causing sister chromatid fusions that initiate breakage/fusion/bridge (B/F/B) cycles. B/F/B cycles occur when fused sister chromatids break during anaphase as their centromeres are pulled in opposite directions. Because breakage does not occur at the site effusion, one daughter cell acquires a chromosome with an inverted repeat at its end, while the other has a chromosome with a terminal deletion. This cycle is then repeated in subsequent cell cycles, resulting in further gene amplification and large terminal deletions. B/F/B cycles continue until the chromosome acquires a new telomere, which we have shown can occur by multiple mechanisms. One of the most common mechanisms is nonreciprocal translocation, which results in the transfer of instability to the chromosome donating the translocation due to the loss of its telomere. As a result, a single DSB near a telomere can result in the instability in multiple chromosomes. This proposal has two specific aims. In the first specific aim, we will address the hypothesis that sister chromatid fusions resulting from DBSs near telomeres result from a deficiency in nonhomologous end joining (NHEJ) near telomeres, as has been demonstrated in yeast. For these studies, we will create an assay system using isogenic cell lines to compare the efficiency of NHEJ at DSBs occurring at various distances from a telomere. We will also use this assay system to address differences in the repair proteins involved in NHEJ and sister chromatid fusion, which has been proposed to involve microhomology-mediated homologous recombinational repair. In the second specific aim, we will address the hypothesis that the p53 and Rb proteins involved in replicative senescence are important in preventing CIN due to DSB-induced telomere loss. In addition, we will establish a genetic screen using green fluorescent protein to monitor the duration of B/F/B cycles to identify additional proteins that can prevent B/F/B cycles. These studies are important in that they will provide new insights into mechanisms of chromosome instability in cancer and lead to new approaches for the development of therapies for preventing CIN in cancer cells.

描述（由申请人提供）：已知哺乳动物细胞暴露于电离辐射中会诱导染色体不稳定性（CIN），这可以促进导致癌症的遗传变化的快速积累。我们已经证明，发生在称为端粒的染色体末端附近的DSB可以通过引起姐妹染色单体融合来促进CIN，从而启动破裂/融合/桥（B/F/B）循环。当融合的姐妹染色单体在后期中断裂时，B/f/b周期会发生，因为它们的中心粒朝相反的方向拉动。由于现场积液不会发生断裂，因此一个子细胞在其末端重复倒入染色体，而另一个则具有带有末端缺失的染色体。然后在随后的细胞周期中重复该循环，从而导致进一步的基因扩增和大末端缺失。 B/F/B周期一直持续到染色体获得新的端粒为止，我们已经证明，可以通过多种机制发生这种端粒。最常见的机制之一是非邻次易位，这导致由于其端粒的损失而导致不稳定性向染色体捐赠的染色体。结果，端粒附近的单个DSB会导致多个染色体的不稳定性。该提议有两个具体的目标。在第一个具体目的中，我们将解决以下假设：端粒附近DBS产生的姐妹染色单体融合是由端粒附近的非同源末端连接（NHEJ）缺乏引起的，正如酵母中所证明的那样。在这些研究中，我们将使用等源性细胞系创建一个测定系统，以比较在远离端粒的不同距离发生的DSB的NHEJ效率。我们还将使用该测定系统来解决NHEJ和姐妹染色单体融合中涉及的修复蛋白的差异，该蛋白质融合了姐妹融合，该蛋白质融合均涉及微学介导的同源重组修复。在第二个特定目的中，我们将解决以下假设：由于DSB诱导的端粒损失，参与复制衰老的p53和Rb蛋白对于预防CIN很重要。此外，我们将使用绿色荧光蛋白来建立一个遗传筛选，以监测B/F/B循环的持续时间，以鉴定可以防止B/F/B周期的其他蛋白质。这些研究很重要，因为它们将为癌症中染色体不稳定性机制提供新的见解，并为开发用于预防癌细胞中CIN的疗法的新方法。