线粒体基因组来源的长非编码RNA通过与p53蛋白的相互作用调控细胞核基因的表达

There is a crosstalk between nucleus and mitochondria, which is established by the coordinated regulation between nuclear and mitochondrial genomes. In addition to miRNA and protein factors, specific nuclear-derived lncRNAs have also been implicated in the regulation of mitochondrial network. However, whether the mitochondrial genome encodes functional lncRNAs, as well as whether the mitochondrial lncRNAs operate in the regulation of nuclear genes, remains to be elucidated. Most of the characterized lncRNAs achieve their biological functions by controlling gene expression, and their interaction with protein is a well-established action mode. With a RNA-SELEX procedure, we have isolated a p53-binding lncRNA, which is encoded by the mitochondrial genome and referred to as mtlncRNA. An interaction between mtlncRNA and p53 inhibits formation of the p53 tetramer, resulting in the loss of its DNA binding activity and repression of p53 targets that include p21. Moreover, mtlncRNA can influence the cell cycle transition from G1 to S phase. These preliminary results prompt the current project to further decode the role of mtlncRNA in controlling nuclear genes. Furthermore, we will determine the regulatory effects of mtlncRNA on cell cycle and apoptosis in the case of H2O2-induced oxidative stress.

细胞核基因组和线粒体基因组之间存在着严密的相互调控关系。除了蛋白质和miRNA，新近研究显示核基因来源的lncRNA也能够调节线粒体功能。然而，线粒体基因组是否能够转录产生功能性lncRNA，这些lncRNA是否能够逆向调控核基因的表达却不得而知。lncRNA通过与蛋白质的相互作用调控基因表达是其发挥生物学功能的重要途径。我们在前期研究中利用自主建立的RNA-SELEX技术筛选到一条与p53蛋白结合、且由线粒体基因组转录的lncRNA，mtlncRNA。初步研究显示mtlncRNA通过抑制p53的四聚化使p53丧失与靶基因启动子结合的能力，从而抑制p21等靶基因的转录，并影响细胞周期的G1/S转换。基于现有基础，本项目将深入研究mtlncRNA对核基因表达的逆向调控和调控机制；并将以细胞周期及细胞凋亡调控为切入点，探讨mtlncRNA在H2O2诱导的氧化应激中的意义。

当前尚不清楚线粒体lncRNA是否能够逆向调控核基因表达。我们发现一条线粒体lncRNA，mtlncRNA1，能够结合p53蛋白，通过抑制p53四聚化使其丧失转录因子活性，从而抑制p21等p53靶基因；mtlncRNA1能够影响细胞周期的G1/S转换，并能增强A549细胞的恶性化表征；并且，mtlncRNA1的功能效应和效应机制具有显著的p53依赖性；mtlncRNA1在肺癌等多种肿瘤组织中高表达，且与肺癌患者的预后密切相关。在项目实施过程中，我们还发现线粒体编码一条mtlncRNA1的反义转录本，mtlncRNA1-AS；mtlncRNA1-AS能够与mtlncRNA1形成双链RNA，可能对mtlncRNA1起到负调节作用。本项目为一2年期面上项目，我们希望在后续工作中进一步研究mtlncRNA1-AS对mtlncRNA1的调节作用，对mtlncRNA1-AS/mtlncRNA1/p53这一调控轴做深入解析。.此外，我们不仅阐释了eRNA作为ncRNA调控基因表达的功能，还揭示了lncRNA OCC-1能够通过阻碍细胞周期的G0/G1和G1/S转换抑制结直肠癌细胞生长。OCC-1通过增强RNA结合蛋白HuR与E3泛素连接酶b-TrCP1的相互作用，促进HuR蛋白的泛素化和水解，从而降低HuR下游靶mRNA分子的胞内水平。该研究表明，lncRNA能够通过介导重要RNA结合蛋白的翻译后修饰，实现对大量mRNA分子的转录后调控，从而构建一个严密的调控网络。.我们还研究了PYCARD-AS1对促凋亡基因PYCARD的表达调控：PYCARD-AS1同时分布于细胞核和细胞质；在细胞核中，PYCARD-AS能够将表观修饰酶DNMT1和G9a招募至PYCARD的启动子区，以顺式作用的形式调控PYCARD；在细胞质中，PYCARD-AS1能够与PYCARD mRNA形成RNA双链，从而通过形成的双链结构以反式作用的方式阻止核糖体在PYCARD mRNA上的装配，抑制PYCARD翻译。我们的研究提示不同亚细胞定位的lncRNA可能具有不同的生物学功能。.目前，本项目已发表2篇SCI论文(Genom. Proteom. Bioinf., IF=6.615; Nucleic Acids Res., IF=11.561)，1篇投稿至PLoS Genet.(Minor Revision)。