Chromosome breakage, pairing and replication: impacts on cell fate and function

项目摘要 本提案描述了三个主要领域的调查，以了解组织如何 细胞核中的染色体以及它们分化为异染色质和常染色质的影响 果蝇的染色体断裂与修复、染色体配对和染色体复制 黑猩猩。在第一部分中，双着丝粒染色体是在雄性生殖系中产生的，在那里它们通常 断裂，将一端断裂的染色体传递给每个子细胞。结构上截然不同的影响 着丝粒和着丝粒组蛋白CenpA的数量对这些染色体的命运将进行检查。 将进行实验，以了解染色体断裂的细胞如何选择自己的命运，修复 或者死亡，以及他们如何在不同的修复模式之间做出选择。这些选择显然与 人类健康。当细胞存活，但不能修复损伤时，它可能会癌变。修复模式可以 确定配子传递的是正常的基因组，还是有缺陷或其他结构变异的基因组 或者突变。一种特殊的修复模式，断裂诱导复制，已知在酵母中具有突变性，并且 与人类的染色体变化有关。通过BIR修复的染色体将被检查以 确定在高等真核生物种系中产生的突变的类型和频率。 在这项工作的第二部分，将研究有丝分裂染色体配对的机制。 在识别促进或抑制配对的基因方面取得了重大进展，但同源性如何 染色体区域相互寻找以启动配对仍然是一个谜。这项工作将测试各种型号的 通过研究重排内部和重排之间的位点特异性重组频率来启动配对 染色体。这项工作也与人类健康有关，因为减数分裂配对的失败可能导致配子 染色体非整倍体。一些癌细胞也表现出不适当的同源配对，这意味着 这些染色体和细胞状态之间可能存在联系。 在拟议工作的第三部分，将研究异染色质中DNA复制的时机。 将测试编码影响异染色质的蛋白质的基因突变，以确定它们对 复制计时。适当地维持异染色质对于基因组的稳定是重要的，并破坏其 正常的复制模式可能会导致基因表达发生变化，从而影响细胞功能和健康。

Project Summary This proposal describes investigations in three main areas to understand how the organization of chromosomes in the nucleus, and their differentiation into heterochromatin and euchromatin, impacts chromosome breakage and repair, chromosome pairing, and chromosome replication in Drosophila melanogaster. In the first part, dicentric chromosomes are generated in the male germline, where they typically break, delivering a chromosome with a broken end to each daughter cell. The influence of structurally distinct centromeres and the amount of centromeric histone CenpA on the fate of these chromosomes will be examined. Experiments will be undertaken to understand how cells with a broken chromosome choose their fate, to repair or to die, and how they choose between different modes of repair. These choices have obvious relevance for human health. When a cell lives, but fails to repair damage, it may become cancerous. The mode of repair can determine whether gametes transmit a normal genome, or a genome with deficiencies or other structural variants or mutations. One particular mode of repair, Break Induced Replication, is known to be mutagenic in yeast, and has been implicated in chromosome change in humans. Chromosomes repaired by BIR will be examined to determine the types and frequencies of mutations produced in the germline of a higher eukaryote. In the second part of this work, the mechanism of mitotic chromosome pairing will be examined. Significant progress has been made in identifying genes that promote or inhibit pairing, but how homologous regions of chromosomes find each other to initiate pairing is still a mystery. This work will test various models for the initiation of pairing by studying the frequency of site-specific recombination within and between rearranged chromosomes. This work also has human health relevance, since failures of meiotic pairing can lead to gametes with chromosomal aneuploidy. Some cancer cells also show inappropriate homologous pairing, implying a possible connection between these chromosome and cellular states. In the third part of the proposed work, the timing of DNA replication in heterochromatin will be examined. Mutations in genes that encode proteins that affect heterochromatin will be tested to determine their effects on replication timing. Proper maintenance of heterochromatin is important for genome stability, and disruption of its normal pattern of replication can lead to altered gene expression, with impacts on cellular function and health.