REGULATION OF POL I TRANSCRIPTION COMPLEX ASSEMBLY

该项目的长期目标是确定RNA聚合酶I (pol I）转录与控制细胞生长的信号有关。 这与人类疾病有关，例如癌症， 基因表达和破坏信号转导通路。 核糖体RNA 核糖体RNA（rRNA）转录提供了一个很好的模型系统， 生长调节基因表达，因为pol I活性是协调的 与细胞的生长状态有关。 这项规定至关重要，因为 rRNA水平直接影响核糖体的产生和细胞的能力， 制造蛋白质。 控制聚合酶I的信号网络 活性在癌细胞中明显失调。 正常细胞 通常依赖血清生长，当它们接触血清时停止生长。 其他细胞。 同样，正常细胞中的pol I转录也下降- 调节血清饥饿或接触抑制。 而血清 独立性和接触抑制的丧失是 肿瘤细胞，如突出的核仁（其中pol I转录需要 地点）。 确定RNA生长调节的生化基础 聚合酶I的重要性有两个主要原因。 首先，它将提供 关于在通信系统之间传输信号的机制的基本信息。 细胞质和细胞核调节真核生物RNA聚合酶活性 细胞 第二，所获得的知识可能有助于寻找毒品 通过阻断RNA聚合酶I的激活来减缓肿瘤细胞的生长。 有证据表明，pol I的转录是受修饰的， 一个或多个关键转录因子或聚合酶本身。 然而，在这方面， 实施控制的手段不明确。 两大假设 与现有数据一致。 一个是对一个或多个 更多的转录因子控制着前起始复合体的组装。 另一种假设是修改一个或多个密钥 激活蛋白影响RNA聚合酶的起始或延伸 转录复合体组装。 拟议的研究将解决这些问题 使用分级转录提取物和纯化的 非洲爪蟾细胞转录因子复合物 用凝胶迁移率变动分析来可视化转录复合物 组装件. 这些研究将开发出识别控制的方法 点的生长调节rRNA基因转录，第一步， 识别信号通路和发挥这种作用的分子 控制

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.