BRF1在RNA聚合酶I指导的基因转录中的作用及其作用机制

How mammalian genes are transcribed is a fundamental question in the research field of molecular biology. Uncovering the regulatory mechanism of gene transcription has profound significance for understanding the molecular basis of life activity. TFII-related factor 1(BRF1) is required for the gene transcription by RNA polymerase III ; abnormal expression of BRF1 leads to cell transformation. Our initial study revealed that BRF1 acts as a nucleolar protein and modulates RNA polymerase I (pol I) transcription in 293T cells. However, what extent does BRF1 act as nucleolar protein? What role does BRF1 play in RNA pol I transcription? How does BRF1 regualte RNA pol I transcription and what biological function has this regulation? Whether BRF1 regulates the expression of other genes or not? These questions have yet to be elucidated. This project aims to investigate and address these issues. The results from the project will not only broaden the insight of the basic mechanism of gene transcription, but also deepen the knowledge of the mechanism that abnormal expression of BRF1 causes tumorigenesis. The results will also provide a theoretical basis for the precaution and therapy of cancer in clinic.

哺乳动物的基因如何转录是分子生物学研究领域中需要解答的最基本问题。揭开基因转录的调节机制对于明白生命活动的分子基础具有重要意义。TFIIB-related factor 1 (BRF1)是RNA 聚合酶III (pol III)基因正常转录所必需的因子；BRF1非正常表达导致细胞转化。我们的初步研究表明，BRF1在293T细胞中充当核仁蛋白并调节RNA聚合酶I的转录。然而，BRF1在多大范围内充当核仁蛋白？BRF1在RNA聚合酶I转录中起什么作用？ BRF1如何调RNA节聚合酶I的转录？以及这种调节具有什么生物功能？BRF1是否也调节其它基因的表达？这些问题仍有待于阐明。本项目针对这些问题进行深入研究和解答。本项目的研究结果将不仅拓宽对基因转录的基本机制的认识，而且加深了解BRF1非正常表达导致肿瘤发生的分子机制。这些结果也为临床上防治癌症奠定理论基础。

RNA聚合酶 Ⅰ and Ⅲ (Pol Ⅰ and Pol Ⅲ)产物占真核细胞至少８５％以上总ＲＮＡ的量，在核糖体生物合成和翻译中起重要调节作用。但是，Pol Ⅰ and Pol Ⅲ　如何协同调节这些过程还不清楚。ＴＦＩＩＢ相关的因子１（BRF１）最早被发现作为ＴＦＩＩＩＢ的亚基参与调节ＲＮＡ聚合酶ＩＩＩ基因转录。在这项研究中，BRF１能被定位到ＳａＯＳ２和ＨｅＬａ　细胞的核仁中，提示BRF１是一个核仁蛋白可能是Ｐｏｌ　Ｉ　基因转录所需要的。的确，我们改变BRF１的表达影响ＰｏｌＩ基因转录和细胞增殖。利用肿瘤细胞的移植裸鼠实验表明，敲低BRF１抑制肿瘤的生长。免疫荧光和免疫印迹分析表明BRF１与ＰｏｌＩ转录器械因子发生互作。染色质免疫沉淀实验表明，BRF１能够结合到ｒＤＮＡ启动子上，改变BRF１的表达影响ＴＢＰ的蛋白水平以及Ｐｏｌ　Ｉ　转录机械组成份在ｒＤＮＡ上的招募。这项研究发现了BRF１　在ＰＯｌ　Ｉ基因转录中的新功能，为Ｐｏｌ　Ｉ　和ＰＯｌ　ＩＩＩ基因转录提供了直接连接，为了解两者的转录产物协同调节核糖体和蛋白质的生物合成提供新视角。