Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, 20133 Milano, Italy.
Proc Natl Acad Sci U S A. 2011 Aug 16;108(33):13647-52. doi: 10.1073/pnas.1108547108. Epub 2011 Aug 1.
UV light induces DNA lesions, which are removed by nucleotide excision repair (NER). Exonuclease 1 (EXO1) is highly conserved from yeast to human and is implicated in numerous DNA metabolic pathways, including repair, recombination, replication, and telomere maintenance. Here we show that hEXO1 is involved in the cellular response to UV irradiation in human cells. After local UV irradiation, fluorescent-tagged hEXO1 localizes, together with NER factors, at the sites of damage in nonreplicating cells. hEXO1 accumulation requires XPF-dependent processing of UV-induced lesions and is enhanced by inhibition of DNA repair synthesis. In nonreplicating cells, depletion of hEXO1 reduces unscheduled DNA synthesis after UV irradiation, prevents ubiquitylation of histone H2A, and impairs activation of the checkpoint signal transduction cascade in response to UV damage. These findings reveal a key role for hEXO1 in the UV-induced DNA damage response linking NER to checkpoint activation in human cells.
紫外线会诱导 DNA 损伤，这些损伤会被核苷酸切除修复（NER）所清除。从酵母到人，外切核酸酶 1（EXO1）都高度保守，它涉及多种 DNA 代谢途径，包括修复、重组、复制和端粒维持。在这里，我们证明 hEXO1 参与了人类细胞对紫外线照射的细胞反应。在局部紫外线照射后，荧光标记的 hEXO1 与 NER 因子一起定位于非复制细胞中损伤部位。hEXO1 的积累需要 XPF 依赖性处理紫外线诱导的损伤，并且可以通过抑制 DNA 修复合成来增强。在非复制细胞中，hEXO1 的耗竭会减少紫外线照射后的非计划性 DNA 合成，阻止组蛋白 H2A 的泛素化，并损害紫外线损伤后检查点信号转导级联的激活。这些发现揭示了 hEXO1 在紫外线诱导的 DNA 损伤反应中的关键作用，将 NER 与人类细胞中检查点的激活联系起来。
