piRNA生成加工通路中重要蛋白质及复合体的结构功能研究

Transposons colonize large parts of animal genome. They are also called Jumping Genes. They can move around, generate mutations and cause genomic instability. Recent studies showed that PIWI-interacting RNAs (piRNAs) have a conserved role in silencing transposons especially in germ cells, because genetic information is transmitted from parental cells to the daughter cells. piRNAs, which are generally 24-32 nucleotides in length. They specifically associate to PIWI proteins and form piRISC complex to silence transposon at both transcriptional and post-transcriptional level. Loss of functions of PIWI or piRNA can cause genome instability and male infertility. To understand the molecular mechanism of piRNA induced transposon silencing, necessitates an improved understanding of protein-protein and protein-RNA interactions in piRNA biogenesis pathway. Although more and more proteins are discovered in this pathway, our knowledge of the exact functions of these proteins remains unclear. Many questions remain to be answered. How RDC complex defines the dual-strand piRNA clusters? Why precursor piRNAs are not spliced? Why some piRNA processing enzymes are mitochondria outer membrane proteins? How is piRNA loaded into the PIWI family proteins?.In this proposal, we propose to study the structure and functions of several protein-protein or protein-RNA complex in piRNA biogenesis pathway, aiming to address the molecular mechanisms of these protein-protein or protein-RNA complex functioning in piRNA biogenesis and transposon silencing.

转座子元件是人类基因组的最大组成成分。转座子又被称为“跳跃基因”，它可以从基因组的一个位置“跳跃”到另一个位置。转座子移动的特性对基因组的完整性和稳定性造成巨大的危险，特别在生殖细胞中，由于其担负着遗传信息由亲代传递给子代的重要任务，转座子的表达需要被严格地调控。因此有机体进化出一种类似于RNAi方式的免疫反应来沉默转座子元件。piRNA是一类在动物生殖谱系细胞中专一性表达的小分子非编码RNA，与PIWI蛋白结合后，通过沉默转座子，保证生殖细胞基因组的稳定性，在配子形成（精子和卵子发生）过程中发挥重要作用，Piwi蛋白和piRNA的缺失或失调会引起不育。本项目将运用各种分子生物学，结构生物学，质谱和Cryo-EM等诸多科学技术，深入研究piRNA生成加工途径中几个重要蛋白-RNA复合物的结构和功能，阐明这些复合物对于果蝇或小鼠生殖细胞的piRNA生成加工及沉默转座子的分子机制。

piRNA是一类生殖细胞特异的小非编码RNA，具有沉默转座子、维持基因组稳定性等功能。piRNA的生成和加工与miRNA或siRNA不同，不依赖于Dicer。piRNA前体主要从标记有H3K9me3的piRNA簇转录产生，并在细胞质中被进一步加工形成成熟的piRNA，在转录水平和转录后水平沉默转座子。在本项目中，我们以几个piRNA生成途径中的关键蛋白复合体为主要研究对象，解析了Rhino-Deadlock复合物、Papi-Piwi复合物结构、Panx-dNxf2复合物结构并揭示这些蛋白复合体在piRNA的生成及其沉默转座子的作用机制。项目执行期间作为（共同）通讯作者在Nature Cell Biology、EMBO Rep、PNAS等期刊发表SCI论文8篇。