MECHANISM OF 5S RNA SYNTHESIS

非洲蛙的5S RNA基因为非洲蛙提供了一个模型系统 用来研究真核基因转录的调控。 体外转录、缺失诱变等技术先行 在这个基因系统中的建立刺激了对许多品种的研究 其他克隆的基因。激活5S RNA基因的第一步是 转录是一个阳性因子的结合，命名为TFIIIA与 基因的中心。将进行实验来测试最近的 预测该蛋白质沿5S共线结合的设计模型 DNA这将涉及构建一个补偿性突变 TFIIIA蛋白，预计将用一种 基因内控制区中心的缺失。一种新的间接方式 我们实验室已经开发了足迹程序，并将其用于 表明这种蛋白也能与主要的卵细胞型5S rna基因结合。 关于体细胞型5S RNA基因。看起来相对贫穷的人 卵母细胞主要基因竞争活性转录的能力 复杂的形成是由以下步骤中的缺陷引起的 转录复合体的形成，如转录的结合 因子TFIIIC与TFIIIA：5S DNA复合体有关。建议进行实验，以 研究活跃的转录复合体形成的阶段，可能是 卵母细胞基因缺陷和体细胞5S RNA点突变 吉恩。这些变异的基因序列也将提供一种研究 染色质结构在转录基因激活中的作用。 特别有兴趣的是确定II型拓扑异构酶 在活性转录复合体的形成中起作用。

The 5S RNA genes of the African frog, Xenopus, provide a model system in which to study the regulation of transcription of eukaryotic genes. Techniques such as in vitro transcription and deletion mutagenesis first established in this gene system have stimulated research on a large variety of other cloned genes. The first step in activation of a 5S RNA gene for transcription is the binding of a positive factor, designated TFIIIA to the center of the gene. Experiments will be performed to test a recently devised model that predicts a colinear binding of this protein along the 5S DNA. This will involve construction of a compensatory mutation in the TFIIIA protein that is predicted to rescue a mutant 5S RNA gene with a deletion in the center of the intragenic control region. A novel indirect footprinting procedure has been developed in our laboratory and used to show that this protein binds as well to the major oocyte type 5S RNA genes as to the somatic type 5S RNA genes. It appears that the relatively poor ability of the major oocyte genes to compete for active transcription complex formation results from a defect in a subsequent step in transcription complex formation, such as the binding of transcription factor TFIIIC to the TFIIIA:5S DNA complex. Experiments are proposed to study the stages in active transcription complex formation that may be defective in both the oocyte gene and point mutants in the somatic 5S RNA gene. These variant gene sequences will also provide a means to study the role of chromatin structure in the activation of genes for transcription. It is of particular interest to determine whether the type II topoisomerase plays a role in formation of active transcription complexes.