核斑小体控制mRNA出核与降解命运不可逆性的功能和机制研究

To ensure efficient and accurate gene expression, the export and degradation of nascent mRNAs need to be controlled. Nuclear speckles are the subnuclear structures, which are widely existed in eukaryotic cells. However, the knowledge of them is still limited. Our recent studies reported that, after transcription, the nascent mRNAs are rapidly sorted to assemble export-competent mRNPs in nuclear speckles or be degraded in nucleoplasm before them passing through nuclear speckles. Up to date, it is unknown why the fate of the sorted mRNAs is irreversible. Our preliminary results showed that the aberrant mRNAs, which should be degraded in nucleus efficiently, prefer to be exported rather than be degraded while the nuclear speckles are disrupted. These results indicated the potential critical function of nuclear speckles in control of the mRNAs for being exported or degraded in nucleus. In this proposal, we plan to combine the biochemical, molecular biological, cell biological and bioinformatical methods to uncover the innovated function and mechanism of nuclear speckles in maintaining the irreversible fate of the sorted mRNAs in export or degradation. Together, this study will significantly advance our understanding for nuclear speckles and provide an important regulation model of the transforming of genetic information.

为确保遗传信息的精准传递，新生转录本的出核和降解需要受到严格的控制。核斑小体是一种高等真核细胞中普遍存在的细胞亚核结构，目前对其功能的了解还十分有限。我们近期研究发现，新生转录本在产生后被快速分选：它们或进入核斑小体中招募出核因子、获得出核能力，或在核质中被快速降解。细胞如何保证这些分选进入出核或降解通路的RNA，按照既定命运出核或降解，至今还不清楚。我们的前期结果表明，当核斑小体被破坏时，原本在核内需要被快速清除的出核异常mRNA不仅未被降解，反而被转运出核，提示核斑小体在控制mRNA降解和出核的命运中发挥重要作用。本项目计划综合运用生物化学、分子生物学、细胞生物学与生物信息学等技术方法，系统研究核斑小体在控制mRNA出核或降解命运不可逆性中的功能，并阐明其发挥功能的分子机制。研究所得结果将拓展我们对于核斑小体功能的认识，并为理解遗传信息的精准传递提供重要调控模式。

核斑小体是一 种哺乳动物细胞中普遍存在的高度动态亚核结构，虽然被发现至今已有七十年历史，但对其功能的认识还仅限于剪接因子的贮存位点，对于其在控制mRNA出核或降解命运方面的功能认识还十分粗线。我们通过APEX2介导的邻位标记技术系统性地鉴定了核斑小体内的蛋白质组；利用高通量RNAi筛选系统，鉴定了显著影响核斑小体形态的蛋白；在此基础上，进一步研究显示RNA进出核斑小体可以确保其形态的维持，进而保证正常RNA的出核，异常RNA被降解。这项研究不仅加深了我们对无膜亚核结构的认识，并为深入理解遗传信息的精准传递核相关疾病发生奠定了理论基础。