Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115, USA.
Mutagenesis. 2010 Jan;25(1):63-9. doi: 10.1093/mutage/gep045. Epub 2009 Nov 9.
Translesion synthesis (TLS) on DNA is a process by which potentially cytotoxic replication-blocking lesions are bypassed, but at the risk of increased mutagenesis. The exact in vivo role of the individual TLS enzymes in Saccharomyces cerevisiae has been difficult to determine from previous studies due to differing results from the variety of systems used. We have generated a series of S.cerevisiae strains in which each of the TLS-related genes REV1, REV3, REV7, RAD30 and POL32 was deleted, and in which chromosomal apyrimidinic sites were generated during normal cell growth by the activity of altered forms of human uracil-DNA glycosylase that remove undamaged cytosines or thymines. Deletion of REV1, REV3 or REV7 resulted in slower growth dependent on (rev3Delta and rev7Delta) or enhanced by (rev1Delta) expression of the mutator glycosylases and a nearly complete abolition of glycosylase-induced mutagenesis. Deletion of POL32 resulted in cell death when the mutator glycosylases were expressed and, in their absence, diminished spontaneous mutagenesis. RAD30 appeared to be unnecessary for mutagenesis in response to abasic sites, as deleting this gene caused no significant change in either the mutation rates or the mutational spectra due to glycosylase expression.
跨损伤合成（TLS）是一种绕过潜在细胞毒性复制阻断损伤的过程，但存在增加突变的风险。由于使用的各种系统得出的结果不同，以前的研究很难确定酿酒酵母中单个 TLS 酶的确切体内作用。我们生成了一系列酿酒酵母菌株，其中每个 TLS 相关基因 REV1、REV3、REV7、RAD30 和 POL32 都被删除，并且在正常细胞生长过程中，通过改变形式的人尿嘧啶-DNA 糖基化酶的活性在染色体上产生了无嘧啶位点，该酶去除未受损的胞嘧啶或胸腺嘧啶。REV1、REV3 或 REV7 的缺失导致生长速度变慢（依赖于 rev3Delta 和 rev7Delta）或增强（依赖于 rev1Delta）突变糖基化酶的表达，并且几乎完全消除了糖基化酶诱导的突变。当表达突变糖基化酶时，POL32 的缺失导致细胞死亡，而在不存在这些酶的情况下，自发突变减少。RAD30 似乎对碱基缺失的突变没有必要，因为删除该基因不会因糖基化酶的表达而导致突变率或突变谱发生显著变化。
