Transcriptional Repression by Maf1 in Yeast

描述（由申请人提供）：rnas和tRNAs的合成通过肿瘤抑制因子（如p53和Rb）和癌基因（如c-myc）的功能与细胞分裂密切相关。这些蛋白的转化形式直接靶向并上调RNA聚合酶（pols） I和III的转录，同时表达重要的细胞周期调节因子。Maf1蛋白是一种独特的转录调节因子，其在人类细胞中的特性与p53和Rb相似。人类Maf1是一种候选肿瘤抑制因子，通过所有三种核RNA聚合酶负调控转录。Maf1如何实现其转录作用尚不清楚，并且由于该蛋白不包含任何已知功能的基序而变得复杂。在酿酒酵母中，Maf1对抑制RNA聚合酶III的转录至关重要，并整合多种营养和应激信号通路的反应，协调调节核糖体和tRNA的合成。这些通路，就像Maf1本身一样，并没有很好的定义。酵母pol III转录抑制中对Maf1的普遍需求为理解核糖体和tRNA合成的调控途径和机制以及这种新型信号整合子的生化功能提供了一个非常有价值的模型。因此，本研究的长期目标是了解Maf1的结构/功能关系，它与调控靶点的相互作用，以及它与上游信号分子的相互作用，这些信号分子通过翻译后机制影响Maf1依赖的转录抑制。这些目标将通过在定义良好的体外系统中进行生化研究，并通过应用一种创新的磷酸肽鉴定方法来实现。此外，强大的全基因组和系统的遗传和生化方法将用于鉴定蛋白激酶和其他参与Maf1信号抑制的分子。最后，通过确定其三维结构，我们将进一步了解Maf1的功能和调控。

DESCRIPTION (provided by applicant): The synthesis of rRNAs and tRNAs is intimately linked with cell division through the function of tumor suppressors (e.g. p53 and Rb) and oncogenes (e.g. c-myc). The transforming forms of these proteins directly target and up-regulate transcription by RNA polymerases (pols) I and III along with the expression of important cell cycle regulators. The Maf1 protein is a unique regulator of transcription whose properties in human cells are similar to p53 and Rb. Human Maf1 is a candidate tumor suppressor that negatively regulates transcription by all three nuclear RNA polymerases. How Maf1 achieves its effects on transcription is not understood and is complicated by the fact that the protein does not contain any motifs of known function. In S. cerevisiae, Maf1 is essential for repressing transcription by RNA polymerase III and functions to integrate the responses from multiple nutritional and stress signaling pathways that coordinately regulate ribosome and tRNA synthesis. These pathways, like Maf1 itself, are not well defined. The universal requirement for Maf1 in pol III transcriptional repression in yeast provides an extraordinarily valuable model for understanding the pathways and mechanisms regulating ribosome and tRNA synthesis and the biochemical function of this novel signal integrator. Accordingly, the long-term goal of this research is to understand Maf1 structure/function relationships, its interactions with regulatory targets and its interactions with upstream signaling molecules that operate via posttranslational mechanisms to affect Maf1-dependent transcriptional repression. These aims will be achieved through biochemical studies in well-defined in vitro systems and through the application of an innovative method for phosphopeptide identification. In addition, powerful genome-wide and systematic genetic and biochemical approaches will be used to identify protein kinases and other molecules involved in signaling repression by Maf1. Finally, our understanding of the function and regulation of Maf1 will be advanced by the determination its three-dimensional structure. PUBLIC HEALTH RELEVANCE: Maf1 is a potential tumor suppressor that negatively regulates transcription by all three nuclear RNA polymerase in mammalian cells. In yeast, Maf1 is an essential mediator of transcriptional repression by RNA polymerase III and integrates the responses from multiple nutritional and stress signaling pathways that coordinately regulate ribosome and tRNA synthesis. Our genetic, biochemical and structural studies on on Maf1 will enhance understanding of fundamental cellular processes that are likely to impact cancer biology.