MOLECULAR MECHANISMS OF DNA REPAIR AND RECOMBINATION IN YEAST

我们正在研究与此相关的独特的染色体代谢事件 与减数分裂和染色体修复接触DNA后 酿酒酵母中的破坏性事件。 的许多基因 修复DNA双链断裂（DSB）所必需的 减数分裂周期的成功完成表明， 过程通过类似的分子机制进行。 中央 这两个组成部分的DSB的修复和成功完成 减数分裂是由RAD 52基因编码的蛋白质。 除了在DSB修复和减数分裂中的作用外，RAD 52似乎还 影响自发有丝分裂重组。 在携带a RAD 52基因的完全缺失重复序列之间的有丝分裂重组 降低;然而，这种降低被伴随的突变阻断 在编码Rho相关核酸酶RhoNUC（RNC 1）的基因中。 这 结果表明，对于自发有丝分裂，RNC 1对RAD 52具有上位性 重组 有趣的是，rnc 1并不能挽救DSB修复， 缺乏或与rad 52相关的减数分裂致死性。 RAD 52在复制过程中的可能作用也正在研究中。 使用一个独特的系统，我们可以测量“切除”的频率， 我们发现，将细菌转座子Tn 5置于酵母LYS 2基因中， 编码DNA聚合酶I或III的基因突变导致高水平的 Tn 5“切除”水平。 “切除”水平升高， polIII或polI菌株减少时，无效突变的RAD 52， 引入这些菌株。 这表明， 被认为是负责DNA滞后链合成的酶， RAD52。 RNC 1似乎在这种相互作用中不起作用， rnc 1 rad 52 polIII突变体仍然被阻断Tn 5“切除”。

We are investigating the unique chromosomal metabolic events associated with meiosis and the repair of chromosomes following exposure to DNA damaging events in the yeast Saccharomyes cerevisiae. Many of the genes necessary for the repair of DNA double strand breaks (DSB) are required for the successful completion of the meiotic cycle suggesting that both processes proceed through similar molecular mechanisms. A central component for both the repair of DSBs and the successful completion of meiosis is the protein encoded by the RAD52 gene. In addition to its role in DSB repair and meiosis, RAD52 appears to influence spontaneous mitotic recombination. In strains carrying a complete deletion of the RAD52 gene mitotic recombination between repeats is reduced; however, this decrease is blocked by a concomitant mutation in the gene encoding the Rho-associated nuclease RhoNUC (RNC1). This result suggests that RNC1 is epistatic to RAD52 for spontaneous mitotic recombination. Interestingly rnc1 does not rescue the DSB repair deficiency or the meiotic lethality associated with rad52. The possible role of RAD52 during replication is also being investigated. Using a unique system whereby we measure the frequency of "excision" of a bacterial transposon Tn5 placed into the yeast LYS2 gene, we have found that mutations in the gene encoding DNA polymerase I or III lead to high levels of Tn5 "excision". The elevated levels of "excision" seen in polIII or polI strains is reduced when a null mutant of RAD52 is introduced into these strains. This suggests an interaction between the enzymes proposed to be responsible for DNA lagging strand synthesis and RAD52. RNC1 does not appear to play a role in this interaction since rnc1 rad52 polIII mutants are still blocked for Tn5 "excision".