含组蛋白变体H3.3核小体组装和去组装的分子机制及其在表观遗传记忆调控中的功能研究

To respond effectively to developmental and enviromental changes, the cells in organisms can “remember” the transcriptional or silencing statuses of genes. The memory can be short memory across mitosis or transgenerational long memory passing through meiosis. The epigenetic memory is one of the critical questions in programming and reprogramming of the cell. The conservative histone H3 variant H3.3 plays important roles in epigenetic memory. Recently, we found that the amino acid residues 87 and 90 in the core domain of Arabidopsis H3.3 guide its deposition to chromatin when the genes are activated, while the amino acid residues 31 and 41 in the N-terminal tail of H3.3 guide its depletion from chromatin when the genes are silenced. Based on our previous important findings, in this project, we plan to identify the key chaperones for the assembly of H3.3 into the nucleosomes and disassembly of H3.3 from the nucleosomes, then define the molecular mechanisms for the regulation of these processes, and address the molecular bases for the regulation of H3.3-mediated epigenetic memory.

为维持生物体个体正常发育和对环境的有效应答，细胞内一些基因的转录或沉默能在细胞分裂前后被“记住”，这可以是通过有丝分裂的短期记忆，也可是通过减数分裂的跨代长期记忆。这种表观遗传记忆是细胞编程和重编程的核心问题之一。生物体内非常保守的组蛋白H3变体H3.3在表观遗传记忆中起到重要的作用。最近我们发现当基因激活时，拟南芥H3.3核心区中的87和90位两个氨基酸介导H3.3加载到具转录活性的染色质上，而当基因沉默时，H3.3氨基端的31和41位氨基酸介导H3.3从核小体上解离。本项目拟以模式植物拟南芥为材料，在前期重要结果基础上，通过鉴定出组蛋白变体H3.3组装入核小体和从核小体上卸载过程中涉及的关键分子伴侣，从而明确含组蛋白变体H3.3的核小体组装和去组装调控的分子机制，进而回答H3.3介导的表观遗传记忆调控的分子基础。

本项目以植物拟南芥为材料，用遗传学、生物化学等交叉手段研究植物组蛋白3变种H3.3整合入染色质和从染色质上解离的分子机制。发表SCI文章五篇，按计划完成。获得了一些重要成果：鉴定出了组蛋白H3.3卸载因子AtFKBP53，该类卸载因子在动植物中都未见报道。还鉴定出了组蛋白H3.3加载因子AtHirA以及AtDEK。发现拟南芥组蛋白H3.3的第31位和第41位氨基酸残基存在着磷酸化修饰。发现转化有H3-K36M的转基因植株，由于异常结合甲基化酶SDG8，导致植物发育异常的原因。设计了一种用于检测活体细胞核内蛋白-蛋白相互作用和核体组装的新方法-核仁牵拉系统。本项目培养博士后出站二人。另还有二名硕博连读研究生毕业并获得三好学生和国家奖学金。