Protein interactions and initiation by RNA polymerase I

描述（由申请人提供）：如果我们要了解正常和异常生长过程，例如伤口愈合和肿瘤形成，则必须了解编码45 S前核糖体RNA的基因的转录机制。核糖体生物发生，因此核糖体RNA基因的表达，与细胞生长的速率相协调，并响应于各种信号，这取决于所研究的细胞类型。本研究的长期目标是确定核糖体RNA基因（rDNA）转录调控的机制。准确和有效的rDNA转录需要至少两个反式作用因子，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，有几种方式，其中rDNA转录的调控。一个是调节RNA聚合酶I启动转录的能力。目前尚不清楚有多少因素控制pol I启动转录的能力。其中两个因子，Rm 3/TIF-IA和TFIC被认为是相同的因子。我们证明了它们是两个不同的因素。酵母Rrn 3基因对于细胞活力是必需的，并且在哺乳动物细胞中的实验证明哺乳动物Rrn 3对于核糖体基因转录是必需的。然而，关于Rrn 3在转录中的作用存在相当大的争议，例如，它是否需要将pol I募集到rDNA启动子中？此外，我们的数据表明，在酵母和哺乳动物细胞中调节Rrn 3功能的机制之间存在根本差异。我们的两个目标集中在确定Rrn 3在rDNA转录中的作用和调节Rrn 3活性的机制。我们的第三个目标集中在PAF 53的作用，第二聚合酶相关因子。一些证据表明，PAF 53是调节rDNA转录的装置的重要组成部分。PAF 53的抗体阻断rDNA转录，并且RNA聚合酶I与PAF 53的缔合与rDNA转录的速率相关。例如，当NIH 3 T3细胞血清饥饿时，PAF 53水平降低，而不是核心RNA聚合酶I水平降低，而血清饥饿导致3 T6细胞中PAF 53与RNA聚合酶I解离。然而，PAF 53在rDNA转录中的作用尚未确定。

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.