Chromatin Degradation During Apoptosis

描述（由申请人提供）：染色体DNA的断裂是细胞凋亡的关键步骤，它可以阻止细胞转录和复制其基因，从而促进细胞杀伤过程。这个过程中的缺陷会导致各种病理状况，包括自身免疫性疾病和癌症。我们已经确定了10个凋亡核酸酶和几个非核酸酶因子参与调节和执行秀丽隐杆线虫的凋亡染色体断裂。它们以序列和CED-3 caspase依赖的方式促进染色体的逐步断裂和降解。这一过程是由一种新的ced -3介导的dicer核糖核酸酶（RNase）转化为脱氧核糖核酸酶（DNase）启动的，后者在染色体上进行第一次切割。与此同时，线粒体核酸酶CPS-6及其激活剂WAH-1从线粒体中释放并转移到细胞核中，在那里它们与其他细胞死亡核酸酶相互作用并合作，以扭转最初的切割

DESCRIPTION (provided by applicant): Fragmentation of chromosomal DNA is a critical step in apoptosis that prevents a cell from transcribing and replicating its genes and thus facilitates the cell killing process. Defects in this process can cause various pathological conditions, including autoimmune disorders and cancer. We have identified ten apoptotic nucleases and several non-nuclease factors involved in regulating and executing apoptotic chromosome fragmentation in C. elegans. They act in a sequential and CED-3 caspase-dependent manner to promote stepwise fragmentation and degradation of chromosomes. The process is initiated by a novel CED-3-mediated conversion of the dicer ribonuclease (RNase) into a deoxyribonuclease (DNase), which makes the first cuts on chromosomes. In parallel, a mitochondrial nuclease CPS-6 and its activator WAH-1 are released from mitochondria and translocated to the nucleus, where they interact and cooperate with other cell death nucleases to turn the initial cuts by dicer into double-strand DNA breaks, leading to fragmentation and degradation of chromosomes. In this proposed work, we will carry out molecular genetic, biochemical, cell biological, and structural analyses to understand these two critical events of apoptotic DNA degradation. In Aim 1, we will investigate the molecular and structural basis underlying CED-3-mediated conversion of the dicer RNase into a DNase. In Aim 2, we will dissect the new signaling pathway that controls cytosolic calcium increase and release of the mitochondrial apoptogeneic factors during apoptosis. In Aim 3, we will perform molecular genetic and functional characterization of two new genes, cps-13 and cps-14, that regulate and coordinate two key cell death execution events, chromosome fragmentation and phosphatidylserine (PS) externalization. These studies should reveal the novel mechanism that controls the specificity and function switch of the dicer nuclease and new signaling mechanisms and players that control the release of the mitochondrial apoptogenic factors.