Topoisomerase I-driven repair of UV-induced damage in NER-deficient cells
Topoisomerase I-driven repair of UV-induced damage in NER-deficient cells
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拓扑异构酶 I 驱动修复 NER 缺陷细胞中紫外线引起的损伤
DOI：
10.1073/pnas.1920165117
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Takeda Shunichi
中科院分区：
文献类型：
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作者：
Saha Liton Kumar;Wakasugi Mitsuo;Akter Salma;Prasad Rajendra;Wilson Samuel H.;Shimizu Naoto;Sasanuma Hiroyuki;Huang Shar-yin Naomi;Agama Keli;Pommier Yves;Matsunaga Tsukasa;Hirota Kouji;Iwai Shigenori;Nakazawa Yuka;Ogi Tomoo;Takeda Shunichi
核苷酸切除修复（NER）去除螺旋去稳定化加合物，包括紫外（UV）损伤、环丁烷嘧啶二聚体（CPD）和嘧啶（6-4）嘧啶酮光产物（6- 4PP）。与CPD相比，6- 4PP具有更大的细胞毒性和更强的DNA螺旋不稳定性。一般认为，NER是去除UV损伤的唯一DNA修复途径，如由先前的数据所证明的，因为在NER缺陷的皮肤成纤维细胞中没有检测到UV损伤的修复。拓扑异构酶I（Topoisomerase I，TOP 1）在基因组双链DNA中不断产生瞬时单链断裂（single strand breaks，SSB），释放扭转应力。停滞的TOP1-SSB复合物可以形成近DNA损伤，包括嵌入染色体DNA中的脱碱基位点和核糖核苷酸。在这里，我们表明，碱基切除修复（BER）增加细胞的耐UV独立NER癌细胞。UV损伤不可逆地捕获稳定的TOP1-SSB复合物附近的UV损伤在NER缺陷的细胞中，和由此产生的SSB激活BER。生化实验表明，6-4PPs有效地诱导稳定的TOP1-SSB复合物，BER的长补丁修复合成去除SSB下游的6-4PPs。此外，NER缺陷癌细胞系在24小时内去除6- 4PP，但不去除CPD，并且去除与TOP1表达相关。NER-deficient皮肤成纤维细胞弱表达TOP1，并且没有显示出可检测的6- 4PP修复。值得注意的是，TOP1在这些成纤维细胞中的异位表达使它们在24 h内完全修复6- 4PP。总之，我们揭示了由TOP 1启动的DNA修复途径，这显著有助于细胞对UV诱导的损伤的耐受性，特别是在过表达TOP 1的恶性癌细胞中。
Nucleotide excision repair (NER) removes helix-destabilizing adducts including ultraviolet (UV) lesions, cyclobutane pyrimidine dimers (CPDs), and pyrimidine (6–4) pyrimidone photoproducts (6–4PPs). In comparison with CPDs, 6–4PPs have greater cytotoxicity and more strongly destabilizing properties of the DNA helix. It is generally believed that NER is the only DNA repair pathway that removes the UV lesions as evidenced by the previous data since no repair of UV lesions was detected in NER-deficient skin fibroblasts. Topoisomerase I (TOP1) constantly creates transient single-strand breaks (SSBs) releasing the torsional stress in genomic duplex DNA. Stalled TOP1-SSB complexes can form near DNA lesions including abasic sites and ribonucleotides embedded in chromosomal DNA. Here we show that base excision repair (BER) increases cellular tolerance to UV independently of NER in cancer cells. UV lesions irreversibly trap stable TOP1-SSB complexes near the UV damage in NER-deficient cells, and the resulting SSBs activate BER. Biochemical experiments show that 6–4PPs efficiently induce stable TOP1-SSB complexes, and the long-patch repair synthesis of BER removes 6–4PPs downstream of the SSB. Furthermore, NER-deficient cancer cell lines remove 6–4PPs within 24 h, but not CPDs, and the removal correlates with TOP1 expression. NER-deficient skin fibroblasts weakly express TOP1 and show no detectable repair of 6–4PPs. Remarkably, the ectopic expression of TOP1 in these fibroblasts led them to completely repair 6–4PPs within 24 h. In conclusion, we reveal a DNA repair pathway initiated by TOP1, which significantly contributes to cellular tolerance to UV-induced lesions particularly in malignant cancer cells overexpressing TOP1.