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.
Fragmentation of chromosomal DNA is a critical step in apoptosis, a cell suicide process that could go awry to cause multiple human diseases. Defects in apoptotic chromosome fragmentation can cause various pathological conditions, including autoimmune disorders and cancer. C. elegans is an excellent animal model for studying basic mechanisms of apoptosis and apoptotic chromosome fragmentation. This proposal seeks to understand the mechanisms that regulate activation of apoptotic nucleases and release of apoptosis factors from mitochondria through important signaling pathways. The studies may identify new genes, pathways, and mechanisms that regulate and execute apoptosis, leading to identification of new therapeutic targets or ideas to treat human disease such as Alzheimer's disease, autoimmune disorders, and cancer that are caused by abnormal apoptosis or DNA degradation.
|Burke, Russell T; Marcus, Joshua M; Orth, James D (2017) Inhibition of exportin-1 function results in rapid cell cycle-associated DNA damage in cancer cells. Oncotarget 8:39460-39475|
|Wang, Yang; Zhang, Yi; Chen, Lianwan et al. (2016) Kinetics and specificity of paternal mitochondrial elimination in Caenorhabditis elegans. Nat Commun 7:12569|
|Conradt, Barbara; Wu, Yi-Chun; Xue, Ding (2016) Programmed Cell Death During Caenorhabditis elegans Development. Genetics 203:1533-62|
|Jain, Saumya; Wheeler, Joshua R; Walters, Robert W et al. (2016) ATPase-Modulated Stress Granules Contain a Diverse Proteome and Substructure. Cell 164:487-98|
|Wheeler, Joshua R; Matheny, Tyler; Jain, Saumya et al. (2016) Distinct stages in stress granule assembly and disassembly. Elife 5:|
|Zhou, Qinghua; Li, Haimin; Li, Hanzeng et al. (2016) Mitochondrial endonuclease G mediates breakdown of paternal mitochondria upon fertilization. Science 353:394-9|
|Zhao, Pei; Zhang, Zhe; Lv, Xiaoying et al. (2016) One-step homozygosity in precise gene editing by an improved CRISPR/Cas9 system. Cell Res 26:633-6|
|Lin, Jason L J; Nakagawa, Akihisa; Skeen-Gaar, Riley et al. (2016) Oxidative Stress Impairs Cell Death by Repressing the Nuclease Activity of Mitochondrial Endonuclease G. Cell Rep 16:279-287|
|Lee, Jason E; Westrate, Laura M; Wu, Haoxi et al. (2016) Multiple dynamin family members collaborate to drive mitochondrial division. Nature 540:139-143|
|Sullivan, Kelly D; Nakagawa, Akihisa; Xue, Ding et al. (2015) Human ACAP2 is a homolog of C. elegans CNT-1 that promotes apoptosis in cancer cells. Cell Cycle 14:1771-8|
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