Mismatch repair proteins recruited to ultraviolet light-damaged sites lead to degradation of licensing factor Cdt1 in the G1 phase.
Mismatch repair proteins recruited to ultraviolet light-damaged sites lead to degradation of licensing factor Cdt1 in the G1 phase.
复制标题
错配修复蛋白被招募到紫外线损伤位点，导致 G1 期许可因子 Cdt1 降解。
DOI：
10.1080/15384101.2017.1295179
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发表时间：
2017
期刊：
影响因子：
4.3
通讯作者：
Nishitani H.
中科院分区：
文献类型：
--
作者：
Tanaka M;Takahara M;Nukina K;Hayashi A;Sakai W;Sugasawa K;Shiomi Y;Nishitani H.
在紫外光(UV)照射下，CDT1被CRL4Cdt2E3泛素连接酶迅速降解。以往的报道表明，核苷酸切除修复(NER)途径是导致CDT1蛋白快速降解的途径。在这里，我们证明了错配修复(MMR)蛋白也参与了紫外线照射后CDT1在G1期的降解。首先，与正常成纤维细胞中CDT1的快速(在∼15分钟内)降解相比，在NER缺陷的XP-A细胞中，CDT1在∼30分钟内保持稳定，但在∼60分钟内被降解。延迟降解还依赖于增殖细胞核抗原和CRL4CDt2。MMR蛋白Msh2和MSH6被招募到处于G1期的XP-A细胞的紫外线损伤部位。用小干扰RNA耗尽这些因子可以阻止XP-A细胞中CDT1的降解。与XP-A细胞中的发现类似，XPA的耗尽延迟了正常成纤维细胞和U2OS细胞中CDT1的降解，而MSH6的共同耗尽进一步阻止了CDT1的降解。此外，MSH6的缺失单独延缓了两种细胞中CDT1的降解。当CDT1的降解被高表达的CDT1减弱时，损伤部位的修复合成受到抑制。我们的研究结果表明，紫外线照射诱导了多条修复途径，激活CRL4CDT2在细胞周期的G1期降解其靶蛋白，导致DNA损伤的有效修复。
Cdt1 is rapidly degraded by CRL4Cdt2E3 ubiquitin ligase after UV (UV) irradiation. Previous reports revealed that the nucleotide excision repair (NER) pathway is responsible for the rapid Cdt1-proteolysis. Here, we show that mismatch repair (MMR) proteins are also involved in the degradation of Cdt1 after UV irradiation in the G1 phase. First, compared with the rapid (within ∼15 min) degradation of Cdt1 in normal fibroblasts, Cdt1 remained stable for ∼30 min in NER-deficient XP-A cells, but was degraded within ∼60 min. The delayed degradation was also dependent on PCNA and CRL4Cdt2. The MMR proteins Msh2 and Msh6 were recruited to the UV-damaged sites of XP-A cells in the G1 phase. Depletion of these factors with small interfering RNAs prevented Cdt1 degradation in XP-A cells. Similar to the findings in XP-A cells, depletion of XPA delayed Cdt1 degradation in normal fibroblasts and U2OS cells, and co-depletion of Msh6 further prevented Cdt1 degradation. Furthermore, depletion of Msh6 alone delayed Cdt1 degradation in both cell types. When Cdt1 degradation was attenuated by high Cdt1 expression, repair synthesis at the damaged sites was inhibited. Our findings demonstrate that UV irradiation induces multiple repair pathways that activate CRL4Cdt2to degrade its target proteins in the G1 phase of the cell cycle, leading to efficient repair of DNA damage.