Mechanism of Polycomb Group (PcG) Gene Silencing

描述（由申请人提供）：拟议研究的目标是更好地理解Polycomb Group （PcG）蛋白介导基因沉默的机制。从人类健康的角度来看，这项工作意义重大，因为它有可能阐明PcG蛋白参与癌症和干细胞生物学的机制。根据目前的pcg介导的基因沉默模型，通过Polycomb蛋白（Pc）和甲基H3赖氨酸27之间的特异性相互作用，EZH2复合物对组蛋白H3的甲基化可以招募PRC-1复合物。虽然PC和甲基化肽之间的特定相互作用已被证明，但与甲基K27在生理相关背景下的相互作用尚未被证明。为了测试该模型，具体目标1是解决PC在核小体背景下与甲基H3 K27特异性相互作用的可能性。在PcG沉默的第二步，同样根据目前的模型，募集的PRC-1复合体使H2A泛素化导致转录抑制。具体目的2是通过建立依赖于H2A泛素化的体外沉默系统来测试该模型。

DESCRIPTION (provided by applicant): The goal of the proposed research is to better understand the mechanism(s) by which the Polycomb Group (PcG) of proteins mediate gene silencing. This work is significant from a human health perspective because it has the potential to illuminate the mechanism of how PcG proteins participate in cancer and stem cell biology. According to current models of PcG-mediated gene silencing, the methylation of histone H3 by the EZH2 complex serves to recruit the PRC-1 complex as a result of specific interactions between the Polycomb protein (Pc) and methyl H3 lysine 27. While a specific interaction between PC and methylated peptides has been shown, an interaction with methyl K27 in a physiologically relevant context has not been demonstrated. To test the model, specific aim 1 is to address the possibility that PC interacts specifically with methyl H3 K27 in the context of nucleosomes. In the second step of PcG silencing, again according to current models, the ubiquitylation of H2A by the recruited PRC-1 complex leads to the inhibition of transcription. Specific aim 2 is to test this model by establishing an in vitro silencing system that depends on H2A ubiquitylation.