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的生长过程，例如伤口愈合和肿瘤形成，了解编码45S前核糖体RNA的基因的转录机制是必不可少的。核糖体的生物发生，以及核糖体RNA基因的表达，是与细胞生长速率相协调的，并根据所研究的细胞类型对各种信号作出反应。我们研究的长期目标是确定核糖体RNA基因（rDNA）转录受到调控的机制。准确和有效的rDNA转录至少需要两个反式作用因子，SL-1和UBF。转录需要SL-1，而UBF激活转录。最近的研究表明，调控rDNA转录有几种方式。一个是对RNA聚合酶I启动转录能力的调控。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rn3/ tfi - 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。酵母的Rrn3基因对细胞活力至关重要，哺乳动物细胞的实验表明，哺乳动物的Rrn3基因对核糖体基因转录至关重要。然而，关于rn3在转录中的作用存在相当大的争议，例如，是否需要它来招募pol I到rDNA启动子？此外，我们的数据表明，酵母和哺乳动物细胞中调控rn3功能的机制存在根本差异。我们的两个目标集中在确定rn3在rDNA转录中的作用和调节rn3活性的机制。我们的第三个目标是关注第二种聚合酶相关因子PAF53的作用。多项证据表明，PAF53是调控rDNA转录装置的重要组成部分。PAF53抗体阻断rDNA转录，RNA聚合酶I与PAF53的关联与rDNA转录率相关。例如，当NIH 3T3细胞处于血清饥饿状态时，PAF53水平降低，而核心RNA聚合酶I水平不降低，而血清饥饿导致3T6细胞中PAF53与RNA聚合酶I分离。然而，PAF53在rDNA转录中的作用尚未明确。

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.