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了解Polycomb Group（PcG）蛋白介导基因沉默的机制。从人类健康的角度来看，这项工作具有重要意义，因为它有可能阐明PcG蛋白如何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，由于Polycomb蛋白（Pc）和甲基H3赖氨酸27之间的特异性相互作用，EZH 2复合物对组蛋白H3的甲基化起到募集PRC-1复合物的作用。虽然PC和甲基化肽之间的特异性相互作用已被证明，与甲基K27在生理相关的背景下的相互作用尚未得到证实。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沉默的第二步中，再次根据目前的模型，通过募集的PRC-1复合物对H2 A的泛素化导致转录的抑制。具体目标2是通过建立依赖于H2 A遍在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.