DNA TOPOISOMERASES AND OTHER ENZYMES AFFECTING CHROMATIN

主要目的是继续研究真核生物在体内的作用。 以酵母为模型体系的DNA拓扑异构酶。两个新酵母菌 Top3和UprI基因的产物拓扑异构酶将是 研究，这些酶的功能重叠与 先前已知的DNA拓扑异构酶I.抑制基因，当 突变、提高生长的各种拓扑异构酶突变株，将被 克隆和分析。两种非洲爪哇的编码基因(S) DNA拓扑异构酶I将被克隆并用于发育研究 调节这些酶的表达。 一种新的遗传系统将被用来研究 参与酵母转录抑制的多种蛋白质 沉默的交配型基因座。这些基因的染色质可能类似于 高等真核生物中的异染色质。此外，还提供了一种新的查找方法 将使用酵母DNA复制基因。最后，一个人的基因 酵母菌十字形切割内切酶将被研究。这种酶 可能参与分解支化重组中间体 被称为霍利迪交叉口。因此，基因突变的影响 这一基因对重组的影响将被研究。

A major aim is to continue studies on the in vivo roles of eukaryotic DNA topoisomerases using yeast as a model system. Two new yeast topoisomerases, products of the TOP3 and UPRI genes, will be investigated, as will the functional overlap of these enzymes with the previously known DNA topoisomerase I. Suppresor genes that, when mutated, improve the growth of various topoisomerase mutants, will be cloned and analyzed. The gene(s) coding for the two forms of Xenopus DNA topoisomerase I will be cloned and used to study the developmentally regulated expression of these enzymes. A novel genetic system will be employed to study interactions among the various proteins involved in transcriptional repression of the yeast silent mating-type loci. The chromatin at these genes may be similar to heterochromatin in higher eukaryotes. Also, a new approach for finding yeast DNA replication genes will be employed. Finally, the gene for a yeast cruciform-cutting endonuclease will be investigated. This enzyme may be involved in resolving the branched recombination intermediate known as the Holliday junction. Therefore, the effect of mutations in this gene on recombination will be studied.