一种新型PRC1变体在不同细胞类型中的结合动态与功能研究

Polycomb group (PcG) proteins are a family of conserved epigenetic regulators with important function for development and cell differentiation. PcG proteins mainly form two types of Polycomb Repressive Complexes (PRCs), named PRC1 and PRC2 - which may collaborate to regulate transcription by mediating histone modification and chromatin compacting. In mammals, the orthologous duplication of core PRC1 components results in the formation of dozens of different variant PRC1 - which may have different biological roles. The study of variant PRC1 is an important focus of Polycomb field, however, variants of PRC1 is rarely reported in Drosophila so far. Our previous study indicated that there may exist a novel type of variant PRC1 in Drosophila which is characterized by the presence of Ph yet lacking of Psc – as far as we know such Psc-absent PRC1 has not been reported in Drosophila or mammals yet. However, it is still unclear about the exact component, binding dynamics and regulatory function of this variant PRC1. Here we propose to using Drosophila S2 and BG3 cells as model, by applying epigenomic centered strategy, to identify other possible components of this variant PRC1, compare its binding dynamics between S2 and BG3 cells, and investigate its function for transcription regulation and role in different cell types. Given the vital roles of PRC1 for epigenetic regulation and the rarity of Drosophila PRC1 variants identified so far, we expect this study will improve the understanding about the complexity, regulatory mechanism and function of drosophila PRC1, and give new insight about the study of mammalian PRC1.

多梳蛋白是一类保守的在发育和细胞分化中起重要功能的表观调控因子。多梳蛋白主要形成两类抑制性复合体（PRC1和PRC2），通过介导组蛋白修饰和染色质结构来调控转录。哺乳动物PRC1由于一些核心蛋白的同源复制可形成数十种变体，且不同变体的功能也有差异。然而目前对果蝇PRC1变体了解很少。我们近期的研究表明果蝇中可能存在一种新型PRC1变体，其特征为具有Ph而缺失Psc – 据我们所知Psc缺失的变体在果蝇和哺乳动物中均未曾报道。但是此变体的具体性质和功能尚不清楚。本项目拟以果蝇S2细胞与BG3细胞为模式，应用以表观组学为核心的手段，鉴定此变体的其它组分，研究其结合位点动态，并通过与基因表达的比较和对靶基因的分析，阐明其转录调控功能和在不同细胞类型中的作用。预期本研究将改善人们对果蝇PRC1的复杂性、调控机理及功能的理解，也会为哺乳动物的相关研究提供新思路。

多梳蛋白主要形成两类抑制性复合体（PRC1/2），通过介导组蛋白修饰和染色质结构来调控转录。虽然Ph和Psc均为果蝇PRC1的核心组分，它们的结合分布存在明显差异。并且，即使Psc(+)Ph(-)位点可能与dRAF复合体相关，之前并没有关于Psc缺失的PRC1变体的报道，因此关于Ph(+)Psc(-)位点的形成机制、性质与功能尚有待研究。本项目以果蝇S2与Kc167细胞为模式，应用以表观组学为核心的手段，针对Ph与Psc的差异结合开展研究。我们应用ChIP-seq技术获得了多种PcG/TrxG相关蛋白以及组蛋白修饰的基因组分布，鉴定了数千个Ph/Psc差异结合位点，明确了相关位点在基因组分布、PcG/TrxG蛋白结合、染色质可及性等方面的特征。并且，Ph与Psc的结合分别与Spps和Pho紧密相关，表明它们的定位机制可能存在差异。有趣的事，Ph与Psc的差异结合在H3K27me3域之外更为明显，并且其在细胞间的结合差异同TrxG、H3K27ac以及染色质可及性显著相关。预期本研究将改善人们对果蝇PRC1复合体的组成与功能的复杂性的理解，并且为哺乳动物的相关研究提供新思路。