piRNA介导的转录沉默的结构与分子机制研究

Transposon accounts for more than 40% of the human genome. Transposons are called jumping genes. They move around and insert into the genome in a variety of ways to cause genome instability. They propagate in their host's germ lines, while the host must in turn try to suppress these parasites. How to silence transposons is extremely challenging While the host develops a "innate immunity" system to distinguish this diversity elements from the protein-coding genes and to selectively silence the former. PIWI-interacting RNAs (piRNAs) are a distinct class of small non-coding RNAs that form the piRNA-induced silencing complex (piRISC) in the germ line of many animal species. The piRISC protects the genome integrity by silencing transposable elements at both transcriptional and post-transcriptional level. However, the molecular mechanism underlying the piRNA mediated transcriptional silencing remains largely unknown. Here, we plan to use a combination of genetic, biochemical, and cellular approaches, to provides the structural and functional insights into the key protein complexes in piRNA mediated transcriptional silencing. This will help to elucidate the molecular mechanisms by which piRNA mediate transcriptional silencing contributes to genomic stability in germ cells as well as diagnosis and treatment of sperm health and male infertility.

转座子占人类基因组的40％以上。它由被称为跳跃基因，从基因组的一个位置移动到另一个位置，并以各种方式插入基因组，导致基因组不稳定。它们在宿主的生殖系统中扩增，而宿主必须反过来抑制转座子的表达。如何沉默转座子是极具挑战性的任务。生物体发展了一套"先天免疫"系统来区分转座子元件与蛋白质编码基因，并选择性沉默前者。PIWI相互作用RNA（piRNA）是一类小非编码RNA。它们与PIWI家族蛋白结合形成piRNA诱导的沉默复合物（piRISC）。piRISC能够在转录和转录后水平沉默转座元件来保护基因组的完整性。然而，对于piRNA介导的转录沉默的分子机制的认知依然十分有限。本项目将运用分子生物学，结构生物学等方法，深入研究piRNA介导的转录沉默中的这些蛋白及其复合体的结构与功能。这将有助于我们阐明piRNA介导的转录沉默对于维持生殖细胞基因组稳定性的分子机制乃至于精子健康和男性不育的诊治。

PIWI相互作用RNA(piRNA)是在生殖系统中特异性表达的小非编码RNA。piRNA与PIWI家族蛋白结合形成piRNA诱导的沉默复合物(piRISC)，在转录和转录后水平沉默转座子以保持基因组完整性。在这个项目中，我们证明Panoramix与dNxf2及其辅助因子dNxt1(p15)一起抑制转座子表达。dNxf2是一种转座子RNA结合蛋白，对于动物生育力和Panoramix介导的转录水平沉默至关重要。此外，我们发现Pandas复合物在Panx介导的转录沉默中起作用，该复合物拮抗了典型的RNA输出机制并将转座子限制在核周。我们的发现对理解RNA代谢如何调节异染色质形成具有广泛的意义。在项目实施过程中，本人作为（共同）通讯作者在Nature Cell Biology、JGG、JBC等期刊发表SCI论文5篇。