GENOMIC STABILITY AND RECOMBINATIONAL INTERACTIONS

基因组内相关重复元件之间的重叠可能 导致相邻序列的改变或易位， 对正常的新陈代谢有潜在的损害。 我们正在调查 酵母中的基因有助于或影响重组 酵母中的分歧DNA之间的关系。 我们检查了修复 在转化含有同源或非同源序列中的缺口的质粒后， 同源染色体DNA（15%发散），使用染色体同源性提供 缺失的信息;我们的观察表明， 不同类型的DNA可能受到不同机制的影响。 我们还 检查了染色体之间的自发有丝分裂重组， 位于含有质粒的着丝粒上的分歧DNA， 先前发现的修复系统的不匹配几乎没有影响， 对同源重组率的影响 令人惊讶的是，两个基因需要 对于许多类型的重组，RAD 51和RAD 52， 在这个系统中同源重组，再次表明一个单独的 分歧DNA之间的重组机制。 我们的研究已经 已扩展到检查紫外诱导的重组分歧 上述质粒-染色体测定中的DNA。 重组是 以与同源DNA大致相同的速率诱导， 与我们实验室以前获得的电离 辐射 在大肠大肠杆菌中，至少有一些类型的重组事件之间的分歧 DNA被错配修复系统抑制或禁止。 我们 检验这种抑制主要是在 异源双链体的初始形成，并且它可能被 预形成异源双链体。 我们之前获得的数据表明， 在大肠大肠杆菌，两种形式的混合物的生存预先形成的，高度 异源双链分子依赖于DNA末端的极性。 我们已经开发出一种技术来净化这两种形式， 个体的依赖性是可以检验的。 修改后， 我们将采取适当的措施， 回答上面提出的问题。

Recombination between related, repeated elements within the genome may lead to alterations in adjacent sequences or translocations, both potentially damaging to normal metabolism. We are investigating which genes in Saccharomyces contribute to or impinge upon recombination between diverged DNAs in yeast (homeologous). We have examined repair following transformation of plasmids containing a gap in homologous or homeologous DNAs (15% diverged), using chromosomal homology to provide the missing information; our observations suggest that repair of the two types of DNAs may be affected by different mechanisms. We have also examined spontaneous mitotic recombination between chromosomes and diverged DNAs located on centromere containing plasmids and established that mismatch previously identified repair systems have little influence on rates of homeologous recombination. Surprisingly, two genes required for many types of recombination, RAD51 and RAD52, had no influence on homeologous recombination in this system, again suggesting a separate mechanism for recombination between diverged DNAs. Our studies have now been extended to the examination of UV-induced recombination of diverged DNAs in the plasmid-chromosome assay described above. Recombination is induced at approximately the same rate as for homologous DNAs, in contrast to results previously obtained in our laboratory for ionizing radiation. In E. coli, at least some types of recombination events between diverged DNAs are inhibited or prohibited by the mismatch repair system. We are testing the hypothesis that this inhibition is largely executed during initial formation of heteroduplexes, and that it might be bypassed by pre-forming heteroduplexes. We previously obtained data suggesting that, in E. coli, the survival of a mixture of two forms of pre-formed, highly heteroduplex molecules depended on the polarity of DNA ends in each form. We have developed a technique for purifying each of the two forms, so that the individual dependences can be examined. After modifications of the procedure to remove minor contaminants, we will be in a position to answer the question posited above.