Protein interactions and initiation by RNA polymerase I

描述(申请人提供)：如果我们要了解正常和异常的生长过程，如伤口愈合和肿瘤形成，了解编码45S核糖体前RNA的基因的转录机制是必不可少的。核糖体生物发生，因此核糖体RNA基因的表达，与细胞生长速度相协调，并对各种信号做出反应，这取决于所研究的细胞类型。我们研究的长期目标是确定核糖体RNA基因(RDNA)转录调控的机制(S)。准确高效的rDNA转录至少需要两个反式作用因子：SL-1和UBF。SL-1是转录所必需的，而UBF激活转录。最近的研究表明，rDNA转录有几种调控方式。其一是对RNA聚合酶I启动转录能力的调节。目前尚不清楚有多少因素控制polI启动转录的能力。其中两个因素Rrn3/TIF-IA和TFIC被认为是相同的因素。我们证明了它们是两个不同的因素。酵母Rrn3基因是细胞存活所必需的，在哺乳动物细胞中的实验证明，哺乳动物的Rrn3对核糖体基因转录是必不可少的。然而，关于Rrn3在转录中的作用存在相当大的争议，例如，它是否需要将PolI招募到rDNA启动子？此外，我们的数据显示了酵母和哺乳动物细胞中调节Rrn3功能的机制之间的根本差异。我们的两个目标集中在确定Rrn3在rDNA转录中的作用和调节Rrn3活性的机制(S)。我们的第三个目标集中在PAF53的作用上，这是第二个聚合酶相关因子。一些证据表明，PAF53是调节rDNA转录的装置的重要组成部分。PAF53抗体阻断rDNA转录，RNA聚合酶I与PAF53的结合与rDNA转录速率相关。例如，当NIH 3T3细胞在血清饥饿时，PAF53水平降低，但不是核心RNA聚合酶I水平降低，而血清饥饿导致3T6细胞中PAF53与RNA聚合酶I的解离。然而，PAF53在rDNA转录中的作用尚不清楚。

DESCRIPTION (provided by applicant): Understanding the mechanism of transcription of the genes that code for 45S pre-ribosomal RNA is essential if we are to understand both normal and abnormal growth processes, e.g. wound healing and neoplasia. Ribosome biogenesis, and therefore the expression of the ribosomal RNA genes, is coordinated with the rate of cell growth, and responds to a variety of signals, depending upon the cell type studied. The long-term objective of our research is to determine the mechanism(s) by which ribosomal RNA gene (rDNA) transcription is regulated. At least two trans-acting factors are required for accurate and efficient rDNA transcription, SL-1, and UBF. SL-1 is required for transcription while UBF activates transcription. Recent studies demonstrate that there are several ways in which rDNA transcription is regulated. One is the regulation of the ability of RNA polymerase I to initiate transcription. It has not been clear how many factors control the ability of pol I to initiate transcription. Two of the factors, Rrn3/TIF-IA and TFIC were believed to be the same factor. We demonstrated that they are two different factors. The yeast Rrn3 gene is essential for cell viability, and experiments in mammalian cells demonstrate that mammalian Rrn3 is essential for ribosomal gene transcription. However, there is considerable controversy concerning the role of Rrn3 in transcription, e.g. is it required for the recruitment of pol I to the rDNA promoter? Moreover, our data demonstrate fundamental differences between the mechanisms that regulate Rrn3 function in yeast and mammalian cells. Two of our goals focus on the determination of the role of Rrn3 in rDNA transcription and the mechanism(s) that regulate Rrn3 activity. Our third aim focuses on the role of PAF53, a second polymerase associated factor. Several lines of evidence suggest that PAF53 is an important component of the apparatus that regulates rDNA transcription. Antibodies to PAF53 block rDNA transcription, and the association of RNA polymerase I with PAF53 correlates with the rate of rDNA transcription. For example, PAF53 levels, but not core RNA polymerase I levels are reduced when NIH 3T3 cells are serum starved, while serum starvation causes the dissociation of PAF53 from RNA polymerase I in 3T6 cells. However, the role of PAF53 in rDNA transcription is yet to be defined.