Control of RNA polymerase I transcription initiation and elongation

描述（由申请人提供）：癌细胞的不受控制的生长不可避免地伴随着RNA聚合酶I活性和核糖体合成的失调。因此，通过RNA聚合酶I控制核糖体RNA转录的机制与细胞转化和肿瘤细胞生长的研究直接相关。该项目的总体目标是表征控制RNA聚合酶I转录起始和延伸的分子机制。对这些调控过程的详细了解将为未来靶向核糖体合成以控制癌细胞生长的治疗策略奠定基础。 RNA聚合酶I的转录起始受生长条件的调节。然而，负责这一调节的机制是复杂的，而且没有完全界定。核心因子是基础RNA聚合酶I转录机制的重要成员，但以前未被确定为核糖体合成调控的靶点。该建议的第一个目标是确定负责调节核心因子活性和丰度的分子机制。 以前的研究，旨在表征RNA聚合酶I转录的控制几乎完全集中在转录的起始步骤。最近，研究表明Spt4p和Spt5p与RNA聚合酶I相互作用，影响转录延伸和体内核糖体RNA加工。本提案的第二个目的是确定Spt4p和Spt5p控制RNA聚合酶I转录延伸的分子机制，并将这种活性与核糖体RNA的加工联系起来。 最近的数据表明，核糖体RNA的加工与RNA聚合酶I的转录延伸偶联。此外，RNA聚合酶I延伸最近被鉴定为调节核糖体合成速率的靶点。然而，很少有影响RNA聚合酶I转录延伸的因素已被确定。因此，需要鉴定和表征控制该酶活性的因素。为了满足这一需求，本提案的第三个目标将表征六个候选转录延伸因子，这些转录延伸因子先前被鉴定为它们在RNA聚合酶II转录中的作用，并且最近已被证明在体内结合核糖体DNA。 公共卫生相关性：这个项目的总体目标是识别和表征真核细胞控制核糖体RNA合成和核糖体组装的机制。长期以来，已知增加的核糖体合成速率与在癌细胞中观察到的增加的细胞增殖速率相关。这些研究将为未来旨在控制细胞生长和增殖的治疗策略奠定基础。

DESCRIPTION (provided by applicant): Uncontrolled growth of cancer cells is inevitably accompanied by dysregulation of RNA polymerase I activity and ribosome synthesis. Thus, the mechanisms that control ribosomal RNA transcription by RNA polymerase I are directly relevant to the study of cell transformation and tumor cell growth. The overall goal of this project is to characterize the molecular mechanisms that control RNA polymerase I transcription initiation and elongation. Detailed understanding of these regulatory processes will lay the foundation for future therapeutic strategies that target ribosome synthesis to control the growth of cancer cells. Initiation of transcription by RNA polymerase I is regulated in response to growth conditions. However, the mechanisms responsible for this regulation are complex and incompletely defined. Core factor is an essential member of the basal RNA polymerase I transcription machinery but has not been previously identified as a target for regulation of ribosome synthesis. The first aim of this proposal will identify the molecular mechanisms responsible for the regulation core factor activity and abundance. Previous studies directed at characterizing the control of RNA polymerase I transcription have focused almost exclusively on the initiation step of transcription. Recently, it was shown that Spt4p and Spt5p interact with RNA polymerase I and influence transcription elongation and ribosomal RNA processing in vivo. The second aim of this proposal will determine the molecular mechanism(s) by which Spt4p and Spt5p control RNA polymerase I transcription elongation and relate this activity to processing of ribosomal RNA. Recent data demonstrate that processing of ribosomal RNA is coupled to transcription elongation by RNA polymerase I. Additionally, RNA polymerase I elongation was recently identified as a target for regulation of ribosome synthesis rates. However, very few factors that influence transcription elongation by RNA polymerase I have been identified. Thus, there is a need to identify and characterize the factors that control this activity of the enzyme. To address this need, the third aim of this proposal will characterize six candidate transcription elongation factors that were previously identified for their roles in RNA polymerase II transcription and have been shown recently to bind the ribosomal DNA in vivo. PUBLIC HEALTH RELEVANCE: The overall goal of this project is to identify and characterize mechanisms by which eukaryotic cells control ribosomal RNA synthesis and ribosome assembly. Increased ribosome synthesis rates have long been known to correlate with the increased cell proliferation rates observed in cancer cells. These studies will lay the foundation for future therapeutic strategies aimed at controlling cell growth and proliferation.