Verhage R A, Zeeman A M, Lombaerts M, van de Putte P, Brouwer J
Laboratory of Molecular Genetics, Leiden Institute of Chemistry, Leiden University, The Netherlands.
Mutat Res. 1996 Feb 15;362(2):155-65. doi: 10.1016/0921-8777(95)00045-3.
The RAD23 gene of Saccharomyces cerevisiae is involved in nucleotide excision repair (NER) and mutations in this gene confer a moderate sensitivity to UV irradiation. However, no repair of either cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts, the major types of lesions formed upon UV irradiation, was detectable during the first 4 h post UV irradiation in a rad23 mutant. rad23, like the rad7 and rad16 mutants, is not as UV sensitive as completely NER-deficient mutants. The rad7 and rad16 mutants are only partly defective in NER: non-transcribed strands are completely refractory to repair while transcription-coupled repair is not affected. To investigate whether the rad23 mutant has similar strand-specific repair characteristics we analyzed gene-specific CPD removal from several loci using strand-specific probes but did not detect any repair. The moderate UV sensitivity of rad23 mutants as compared to completely NER-deficient mutants is therefore not due to gene- or strand-specific removal of lesions, indicating that rad23 mutants do not have a similar repair defect as rad7 or rad16 mutants, but are presumably defective in general NER. The rad23 mutation does not suppress the high UV sensitivity of completely NER-deficient rad1 or rad14 strains. This demonstrates that the relatively high survival of rad23 mutants in not due to an increased tolerance for the lesions that seem to persist in the genome but rather requires some NER function.
酿酒酵母的RAD23基因参与核苷酸切除修复（NER），该基因的突变会使细胞对紫外线照射产生中度敏感性。然而，在紫外线照射后的最初4小时内，在rad23突变体中未检测到对紫外线照射后形成的主要损伤类型——环丁烷嘧啶二聚体（CPDs）和6-4光产物的修复。与rad7和rad16突变体一样，rad23不像完全缺乏NER的突变体那样对紫外线敏感。rad7和rad16突变体在NER中仅部分存在缺陷：非转录链完全无法修复，而转录偶联修复不受影响。为了研究rad23突变体是否具有类似的链特异性修复特征，我们使用链特异性探针分析了几个基因座上基因特异性CPD的去除情况，但未检测到任何修复。因此，与完全缺乏NER的突变体相比，rad23突变体的中度紫外线敏感性并非由于基因或链特异性的损伤去除，这表明rad23突变体与rad7或rad16突变体没有类似的修复缺陷，但可能在一般的NER中存在缺陷。rad23突变不能抑制完全缺乏NER的rad1或rad14菌株的高紫外线敏感性。这表明rad23突变体相对较高的存活率并非由于对基因组中似乎持续存在的损伤具有更高的耐受性，而是需要一些NER功能。
