Yasuhira S, Morimyo M, Yasui A
Institute of Development, Aging, and Cancer, Tohoku University, Seiryomachi 4-1, Aoba-Ku, Sendai 980-8575, Japan.
J Biol Chem. 1999 Sep 17;274(38):26822-7. doi: 10.1074/jbc.274.38.26822.
Fission yeasts Schizosaccharomyces pombe possess two types of excision repair systems for UV-induced DNA damage, nucleotide excision repair (NER) and UV-damaged DNA endonuclease (UVDE)-dependent excision repair (UVER). Despite its high efficiency in damage removal, UVER defects have less effect on UV survival than NER defects. To understand the differential roles of two pathways, we examined strand-specific damage removal at the myo2 and rpb2 loci. Although NER removes cyclobutane pyrimidine dimers from the transcribed strand more rapidly than from the nontranscribed strand, UVER repairs cyclobutane pyrimidine dimers equally on both strands and at a much higher rate than NER. The low rate of damage removal from the nontranscribed strand in the absence of UVER indicates inefficient global genome repair (GGR) in this organism and a possible function of UVER as an alternative to GGR. Disruption of rhp26, the S. pombe homolog of CSB/RAD26, eliminated the strand bias of NER almost completely and resulted in a significant increase of UV sensitivity of cells in a uvdeDelta background. We suggest that the combination of transcription-coupled repair of NER and rapid UVER contributes to UV survival in growing S. pombe cells, which is accomplished by transcription-coupled repair and GGR in other organisms.
裂殖酵母粟酒裂殖酵母拥有两种针对紫外线诱导的DNA损伤的切除修复系统，即核苷酸切除修复（NER）和紫外线损伤DNA内切酶（UVDE）依赖性切除修复（UVER）。尽管UVER在去除损伤方面效率很高，但与NER缺陷相比，UVER缺陷对紫外线存活的影响较小。为了了解这两条途径的不同作用，我们检测了肌动蛋白2（myo2）和RNA聚合酶II第二大亚基（rpb2）基因座上的链特异性损伤去除情况。尽管NER从转录链上比从非转录链上更快地去除环丁烷嘧啶二聚体，但UVER在两条链上均等地修复环丁烷嘧啶二聚体，且修复速率比NER高得多。在没有UVER的情况下，从非转录链上去除损伤的速率较低，这表明该生物体中的全基因组修复（GGR）效率低下，并且UVER可能具有替代GGR的功能。粟酒裂殖酵母中CSB/RAD26的同源物rhp26的破坏几乎完全消除了NER的链偏向性，并导致在uvdeDelta背景下细胞的紫外线敏感性显著增加。我们认为，NER的转录偶联修复和快速的UVER相结合有助于生长中的粟酒裂殖酵母细胞的紫外线存活，而在其他生物体中这是通过转录偶联修复和GGR来实现的。
