GENETIC CONTROL OF SISTER CHROMATID EXCHANGE IN YEAST

姐妹染色单体重组的机制较差。 在基因和分子水平上被理解。因为它可能是 在修复、突变和基因放大方面很重要，我们有 启动研究以表征这一过程并调查 酿酒酵母的遗传控制。姐妹 染色单体重组是通过重组来测量的 HIS3基因的两个片段共享300个碱基对 同源区域。它们的排列方式是 重组将产生一个完整的基因。我们已经展示了 参与DNA修复的几个基因需要 在野生型细胞中观察到的水平。基因的突变 增强或抑制同源染色体重组 姐妹染色单体重组过程中的功能相似。 DNA损伤剂可以显著增强这一过程。 尽管细胞对x射线诱导的交换具有抵抗力。 已经分离出突变体，它们要么可以导致增强 交换水平(ESR)或抑制水平(DSR)。三个突变体 (ESR1、ESR2、ESR3)已被广泛研究。每一个 这些突变体的行为就像一个单一的孟德尔基因。ESR1和 ESR2具有更高的有丝分裂基因转换水平。 克隆esr1、esr2和esr3基因的实验正在进行中。 通过互补。

The mechanism of sister chromatid recombination is poorly understood at the genetic and molecular level. Since it may be important in repair, mutagenesis and gene amplification, we have initiated studies to characterize the process and investigate the genetic control in the yeast Saccharomyces cerevisiae. Sister chromatid recombination is measured by recombination between two fragments of the HIS3 gene which share a 300 base pair region of homology. They are arranged in such a way that recombination will generate a complete gene. We have shown that several of the genes involved in DNA repair are required for the levels observed in wild type cells. Mutations in genes that enhance or depress homologous chromosome recombination have similar function son the sister chromatid recombination process. DNA damaging agents can considerably enhance the process although the cells are resistant to x-ray induced exchange. Mutants have been isolated which can either lead to enhanced levels (esr) or depressed (dsr) levels of exchange. Three mutants (esr1, esr2, esr3) have been characterized extensively. Each of these mutants behaves like a single Mendelian locus. esr1 and esr2 have elevated levels of mitotic gene conversion. Experiments are underway to clone the esr1, esr2, and esr3 genes by complementation.