REGULATION OF POL I TRANSCRIPTION COMPLEX ASSEMBLY

这个项目的长期目标是确定RNA聚合酶是如何 (POL I)转录与控制细胞生长的信号有关。 这与人类疾病有关，如癌症，涉及改变 基因表达和信号转导通路中断。核糖体RNA (RRNA)转录为研究提供了一个很好的模型系统 因为PolI活性是协调的，所以生长调控的基因表达 与细胞的生长状态有关。这一规定至关重要，因为 RRNA水平直接影响核糖体的生产和细胞的能力 制造蛋白质。控制聚合酶I的相同信号网络 癌细胞中的活动显然是不受调控的。正常细胞是 一般依赖血清生长，当他们接触时停止生长 其他细胞。同样，正常细胞中的PolI转录也下降了- 受血清饥饿或接触抑制的影响。然而，血清 独立性和丧失接触抑制是 肿瘤细胞，如突出的核仁(PolI转录在那里进行 地点)。确定RNA生长调控的生化基础 聚合酶I之所以重要，主要有两个原因。首先，它将提供 之间传输信号的机制的基本信息 真核生物中调节RNA聚合酶活性的细胞质和细胞核 细胞。其次，所获得的知识可能有助于寻找毒品 它可以通过阻断RNA polI的激活来减缓肿瘤细胞的生长。 有证据表明，polI的转录是通过修饰 一个或多个关键转录因子或聚合酶本身。然而， 实施控制的手段尚不清楚。两个主要假设 与现有数据一致。一种是修改其中一个或 更多的转录因子控制着预起始复合体的组装。 另一种假设是修改一个或多个密钥 激活蛋白影响RNA聚合酶的启动或延伸 转录复合体组装。拟议的研究将解决这些问题 使用分级转录提取和纯化的假设 非洲爪哇培养细胞转录因子复合体的偶联 用凝胶迁移率改变分析来可视化转录复合体 集合。这些研究将开发识别控制的方法 生长调节rRNA基因转录的点，这是 识别作用于此的信号通路和分子 控制力。

The long-term goal of this project is to determine how RNA polymerase I (pol I) transcription is linked to the signals that control cell growth. This is relevant to human diseases such as cancer that involve altered gene expression and disrupted signal transduction pathways. Ribosomal RNA (rRNA) transcription provides an excellent model system in which to study growth regulated gene expression because pol I activity is coordinated with the growth status of the cell. This regulation is crucial because rRNA levels directly affect ribosome production and the cell's capacity to make proteins. The same signalling networks that control polymerase I activity are apparently deregulated in cancer cells. Normal cells are generally dependent on serum for growth and stop growing when they contact other cells. Likewise, pol I transcription in normal cells is down- regulated upon serum starvation or contact inhibition. However, serum independence and loss of contact inhibition are common characteristics of tumor cells, as are prominent nucleoli (where pol I transcription takes place). Determining the biochemical basis for growth regulation of RNA polymerase I is important for two major reasons. First, it will provide basic information about the mechanisms that transmit signals between the cytoplasm and nucleus to modulate RNA polymerase activity in eukaryotic cells. Second, the knowledge gained may facilitate the search for drugs that can slow the growth of tumor cells by blocking RNA pol I activation. Evidence suggests that pol I transcription is regulated by modification of one or more key transcription factors or the polymerase itself. However, the means by which control is exerted are unclear. Two major hypotheses are consistent with available data. One is that modification of one or more transcription factors controls assembly of the preinitiation complex. An alternative hypothesis is that modification of one or more key activator proteins affects RNA polymerase initiation or elongation after transcription complex assembly. The proposed research will address these hypotheses using fractionated transcription extracts and purified transcription factor complexes from cultured Xenopus laevis cells coupled with a gel mobility shift assay to visualize transcription complex assembly. These studies will develop the methods to identify control points in growth-regulated rRNA gene transcription, a first step in the identification of signalling pathways and molecules that exert this control.