Proteasomal regulation of proliferation in the C. elegans germ line

点击翻译按钮获取中文摘要

Stem cells are essential for proper development and tissue homeostasis in multicellular organisms. They are able to fulfill these functions due, in part, to their unique ability to produce both self-renewing and differentiating daughter cells. Differentiating daughter cells form the desired tissue, while self-renewing daughter cells retain their stem cell character and maintain the stem cell population. The overall program in my lab is to understand how stem cell behaviour is controlled. We use the C. elegans germ line as a model, which maintains a stem cell population in the distal end of each gonad arm, allowing the worm to produce thousands of gametes throughout its life. The combined expression of certain proteins (proliferation-promoting proteins) provides stem cells with their identity and ability to self-renew; therefore, characterization of these proteins will provide significant insight into stem cell behaviour and function. We identified proteasomal degradation as a key mechanism in controlling the accumulation of proliferation-promoting proteins. The goal of the research described in this proposal is to characterize how proteasomal degradation contributes to the regulation of stem cell self-renewal. We have already conducted an RNAi screen and identified five substrate recognition subunits (SRSs) of E3-ubiquitin ligases that participate in controlling stem cell self-renewal. We will first characterize how one of these SRSs, RFP-1, controls the accumulation of the MRG-1 chromodomain protein, which we identified as a promoter of stem cell proliferation. Our genetic analysis has also demonstrated that RFP-1 cannot be the only SRS that targets MRG-1 for degradation. Therefore, we will identify these other SRSs and determine how they coordinate their activity with RFP-1. We will then perform genetic analyses of the other four SRSs that we identified in our initial RNAi screen to identify what aspect of stem cell function could be controlled by each of them. Next, we will identify and characterize the protein targets of each SRS, and confirm that protein degradation contributes to their pattern of accumulation. Finally, we will conduct a genetic screen as an independent approach to identify proliferation-promoting proteins. Identification of these proteins, and gaining an understanding of how their activity is controlled by protein degradation, will provide significant insights into how stem cell behaviour is controlled.**