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: 7623945
• 负责人: John P. Murnane
• 金额: $ 23.97万
• 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/7623945
• 关键词: Address; Affect; Anaphase; Appearance; Biological Assay; Cell Aging; Cell Cycle; Cell Cycle Regulation; Cell Cycle Regulation Pathway; Cell Line; Cells; Centromere; Chromosomal Instability; Chromosomes; Clinical Protocols; Clone Cells; Complex; DNA Repair; DNA Sequence Rearrangement; DNA repair protein; Double Strand Break Repair; Event; Fibroblasts; Gene Amplification; Genes; Genetic Screening; Green Fluorescent Proteins; Human; Ionizing radiation; Knock-out; Lead; Malignant Neoplasms; Mammalian Cell; Mediating; Monitor; Mus; Mutation; Pathway interactions; Process; Proteins; Radiation Induced DNA Damage; Research Personnel; Retinoblastoma Protein; Sister Chromatid; Site; Small Interfering RNA; Structure; System; TP53 gene; Telomerase; Yeasts; cancer cell; daughter cell; effusion; endonuclease; insight; interstitial; novel; novel strategies; prevent; protein function; recombinational repair; repaired; response; senescence; telomere; therapy development

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会诱导染色体不稳定（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，发生在染色体末端（称为端粒）附近的dsb可以通过引起姐妹染色单体融合来促进CIN，从而启动断裂/融合/桥接（B/F/B）循环。当融合的姐妹染色单体在后期分裂时，它们的着丝粒被拉向相反的方向，就会发生B/F/B循环。由于在渗出部位不发生断裂，一个子细胞得到一条末端有反向重复的染色体，而另一个子细胞得到一条末端有缺失的染色体。这个循环在随后的细胞周期中重复，导致进一步的基因扩增和大量的末端缺失。B/F/B循环继续进行，直到染色体获得新的端粒，我们已经证明这可以通过多种机制发生。最常见的机制之一是非互反易位，由于端粒的丢失，导致不稳定性转移到提供易位的染色体上。因此，端粒附近的单个DSB可能导致多个染色体的不稳定性。这项建议有两个具体目的。在第一个具体目标中，我们将解决由端粒附近的DBSs引起的姐妹染色单体融合是由于端粒附近的非同源末端连接（NHEJ）缺陷造成的，正如在酵母中所证明的那样。对于这些研究，我们将创建一个使用等基因细胞系的检测系统，以比较NHEJ在距离端粒不同距离的dsb上的效率。我们还将使用该分析系统来解决涉及NHEJ和姐妹染色单体融合的修复蛋白的差异，这涉及微同源介导的同源重组修复。在第二个特定目标中，我们将解决p53和Rb蛋白参与复制性衰老在预防由dsb诱导的端粒丢失引起的CIN中起重要作用的假设。此外，我们将利用绿色荧光蛋白建立基因筛选来监测B/F/B周期的持续时间，以确定可以阻止B/F/B周期的其他蛋白。这些研究具有重要意义，因为它们将为癌症染色体不稳定的机制提供新的见解，并为开发预防癌细胞中CIN的治疗方法提供新的途径。