Cell proliferation and DNA breaks are involved in ultraviolet light-induced apoptosis in nucleotide excision repair-deficient Chinese hamster cells
Cell proliferation and DNA breaks are involved in ultraviolet light-induced apoptosis in nucleotide excision repair-deficient Chinese hamster cells
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DOI：
10.1091/mbc.01-05-0225
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发表时间：
2002-01-01
影响因子：
3.3
通讯作者：
Kaina, B
中科院分区：
文献类型：
--
作者：
Dunkern, TR;Kaina, B
紫外光同时瞄准膜受体和核DNA，从而激发触发细胞凋亡的信号。虽然受体介导的细胞凋亡已经得到了广泛的研究，但DNA损伤在细胞凋亡中的作用尚不清楚。为了分析紫外线诱导的DNA损伤在细胞凋亡中的重要性，我们比较了核苷酸切除修复(NER)缺陷的中国仓鼠卵巢细胞(27-1和43-3B分别突变了修复基因ERCC3和ERCC1)和相应的DNA修复熟练的成纤维细胞(CHO-9和ERCC1互补的43-3B细胞)。NER缺失的细胞对诱导细胞凋亡高度敏感，表明UV-C光诱导的细胞凋亡是由于DNA碱基损伤未修复所致。然而，未修复的损伤并不直接激活凋亡途径，因为UV-C照射下的细胞凋亡需要DNA复制和细胞增殖。研究还表明，在NER缺失的细胞中，未修复的损伤通过先于凋亡的复制依赖过程转化为DNA双链断裂(DSB)和染色体异常。因此，我们认为，含有未修复损伤的DNA复制所产生的DSB是UV-C诱导的细胞凋亡的最终触发因素。UV-C光诱导的细胞凋亡与Bcl2的表达水平下降和caspase的激活有关。Bcl2的下降和随后的细胞凋亡也可能至少部分是由UV-C诱导的转录阻断引起的，这在NER缺陷的细胞中比在野生型细胞中更明显。这与用放线菌素D进行的实验是一致的，放线菌素D会导致Bcl-2下降和细胞凋亡。UV-C诱导的DNA损伤、复制依赖的DSB形成和线粒体损伤途径的激活导致的细胞凋亡不依赖于细胞突变所针对的功能P53。
UV light targets both membrane receptors and nuclear DNA, thus evoking signals triggering apoptosis. Although receptor-mediated apoptosis has been extensively investigated, the role of DNA damage in apoptosis is less clear. To analyze the importance of DNA damage induced by UV-C light in apoptosis, we compared nucleotide excision repair (NER)-deficient Chinese hamster ovary cells (lines 27-1 and 43-3B mutated for the repair genes ERCC3 and ERCC1, respectively) with the corresponding DNA repair-proficient fibroblasts (CHO-9 and ERCC1 complemented 43-3B cells). NER-deficient cells were hypersensitive as to the induction of apoptosis, indicating that apoptosis induced by UV-C light is due to unrepaired DNA base damage. Unrepaired lesions, however, do not activate the apoptotic pathway directly because apoptosis upon UV-C irradiation requires DNA replication and cell proliferation. It is also shown that in NER-deficient cells unrepaired lesions are converted into DNA double-strand breaks (DSBs) and chromosomal aberrations by a replication-dependent process that precedes apoptosis. We therefore propose that DSBs arising from replication of DNA containing nonrepaired lesions act as an ultimate trigger of UV-C-induced apoptosis. Induction of apoptosis by UV-C light was related to decline in the expression level of Bcl-2 and activation of caspases. Decline of Bcl-2 and subsequent apoptosis might also be caused, at least in part, by UV-C-induced blockage of transcription, which was more pronounced in NER-deficient than in wild-type cells. This is in line with experiments with actinomycin D, which provoked Bcl-2 decline and apoptosis. UV-C-induced apoptosis due to nonrepaired DNA lesions, replication-dependent formation of DSBs, and activation of the mitochondrial damage pathway is independent of functional p53 for which the cells are mutated.