Mechanism of Polycomb Group (PcG) Gene Silencing

描述(申请人提供)：拟议研究的目标是更好地了解蛋白质多梳基(PcG)介导基因沉默的机制(S)。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蛋白如何参与癌症和干细胞生物学的机制。根据目前PcG介导的基因沉默模型，EZH2复合体对组蛋白H3的甲基化作用是聚梳蛋白(Pc)与甲基H3赖氨酸27特异性相互作用的结果。虽然已经显示了PC和甲基化多肽之间的特定相互作用，但在生理相关的背景下还没有证明与甲基K27之间的相互作用。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H3K27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，招募的PRC-1复合体泛素化H2A导致转录抑制。具体目标2是通过建立依赖于H2A泛素化的体外沉默系统来测试这一模型。

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.