The Role of Yeast Mediator in Transcriptional Regulation

介体是一种全球转录共调节蛋白复合体，在细胞周期调控中发挥核心作用。 RNA聚合酶II转录基因的激活和抑制。高度保守的 调解人的组成和功能，以及其错综复杂的机制，使 酿酒酵母是深入分子研究的理想模型。当前的范式 For Mediator的功能是作为DNA结合激活剂之间的直接中介 和通用的转录机器。然而，酵母基因研究揭示了两个 与这一简单模型不兼容的复合体的重要功能属性。 第一个是Mediator通过可能的 连接到染色质结构。二是额外的共激活剂络合物和特异性 激活转录中介体功能所需的核心启动子序列。虽然 在过去的10到15年里，人们对酵母基因技术所研究的能力知之甚少 Mediator用来促进这些功能的直接机制。我们建议的研究 通过使用生物化学实验来揭示这些的机理基础，以满足关键需求 中介体的新功能特性。 我们研究计划的长期目标是获得一个完整的分子 理解激活或抑制信号与核心之间的“交流” 真核细胞中的转录机制。我们建议的酵母介体研究中心在 使用纯化的蛋白质和核酸来阐明机制。他们还召集了 酵母中丰富的遗传、基因组和蛋白质组资源以了解这些 生理环境中的机制。我们的中心假设是，调解人促进了 抑制和与其他协同激活者通过不同于 作为激活剂和RNA聚合酶之间的直接中间体II.具体目的 将回答两个关键问题。首先，调解人是如何促成的 与染色质为基础的转录抑制有关吗？我们提出了生物化学和遗传学 解释压抑机制的实验，这种机制涉及 介体和染色质。第二，SAGA、TFIID和核心启动子序列如何影响 介体激活转录？我们设计了生化实验来确定 如果Mediator直接与不同的共激活剂协同工作，以刺激高水平的激活 以合作的方式转录。这些研究对于全面理解 用于调节细胞和发育过程的转录机制。

Mediator is a global transcriptional co-regulatory protein complex that plays a central role in the activation and repression of RNA polymerase II transcribed genes. The highly conserved composition and function of Mediator, as well as the intricacies of its mechanism, make Saccharomyces cerevisiae an ideal model for incisive molecular studies. The current paradigm for Mediator function is that it serves as a direct intermediary between DNA-bound activators and the general transcription machinery. However, yeast genetic studies have revealed two important functional properties of the complex that are not compatible with this simple model. The first is Mediator's ability to repress transcription of a large number of genes via a possible link to chromatin structure. The second is the additional co-activator complexes and specific core promoter sequences required for Mediator function in activated transcription. Although ably studied by yeast genetic techniques over the past 10 to 15 years, very little is known about the direct mechanisms used by Mediator to facilitate these functions. Our proposed research meets a critical need by using biochemical experiments to reveal the mechanistic basis of these novel functional properties of Mediator. The long-term goal of our research program is to obtain a complete molecular understanding of the 'communication' between activation or repression signals and the core transcription machinery in eukaryotic cells. Our proposed studies of yeast Mediator center on the use of purified proteins and nucleic acids to elucidate mechanisms. They also marshal the substantial genetic, genomic and proteomic resources in yeast to understand these mechanisms in a physiological context. Our central hypothesis is that Mediator facilitates repression and co-operates with other co-activators through mechanisms that are distinct from serving as a direct intermediary between activators and RNA Polymerase II. The specific aims of the current research project will answer two key questions. First, how are Mediator-facilitated and chromatin-based transcription repression linked? We propose biochemical and genetic experiments to elucidate a mechanism of repression that involves direct interactions between Mediator and chromatin. Second, how do SAGA, TFIID, and core promoter sequence affect Mediator activated transcription? We have designed biochemical experiments to determine how and if Mediator directly works with different co-activators to stimulate high levels of activated transcription in a cooperative manner. These studies are essential to understand the full range of transcriptional mechanisms used to regulate cellular and developmental processes.