Nucleotide excision repair (NER) is a conserved, flexible mechanism responsible for the removal of bulky, helix-distorting DNA lesions, like ultraviolet damage or cisplatin adducts, but its role in the repair of lesions generated by oxidative stress is still not clear. The helicase XPD/ERCC2, one of the two helicases of the transcription complex IIH, together with XPB, participates both in NER and in RNA pol II-driven transcription. In this work, we investigated the responses of distinct XPD-mutated cell lines to the oxidative stress generated by photoactivated methylene blue (MB) and KBrO3 treatments. The studied cells are derived from patients with XPD mutations but expressing different clinical phenotypes, including xeroderma pigmentosum (XP), XP and Cockayne syndrome (XP-D/CS) and trichothiodystrophy (TTD). We show by different approaches that all XPD-mutated cell lines tested were sensitive to oxidative stress, with those from TTD patients being the most sensitive. Host cell reactivation (HCR) assays showed that XP-D/CS and TTD cells have severely impaired repair capacity of oxidised lesions in plasmid DNA, and alkaline comet assays demonstrated the induction of significantly higher amounts of DNA strand breaks after treatment with photoactivated MB in these cells compared to wild-type cells. All XPD-mutated cells presented strong S/G2 arrest and persistent γ-H2AX staining after photoactivated MB treatment. Taken together, these results indicate that XPD participates in the repair of lesions induced by the redox process, and that XPD mutations lead to differences in the response to oxidatively induced damage.

中文翻译：

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XPD / ERCC2突变会干扰细胞对氧化应激的反应。

核苷酸切除修复（NER）是一种保守的，灵活的机制，负责清除庞大的，扭曲螺旋的DNA损伤，例如紫外线损伤或顺铂加合物，但其在修复氧化应激产生的损伤中的作用尚不清楚。转录复合物IIH的两种解旋酶之一XPD / ERCC2解旋酶与XPB一起参与NER和RNA pol II驱动的转录。在这项工作中，我们调查了不同的XPD突变细胞系对光活化亚甲基蓝（MB）和KBrO3处理产生的氧化应激的反应。所研究的细胞来自具有XPD突变但表达不同临床表型的患者，包括色素干性皮肤病（XP），XP和Cockayne综合征（XP-D / CS）和三硫代营养不良症（TTD）。我们通过不同的方法表明，所测试的所有XPD突变细胞系均对氧化应激敏感，而来自TTD患者的细胞系最为敏感。宿主细胞激活（HCR）分析表明，XP-D / CS和TTD细胞严重破坏了质粒DNA中氧化损伤的修复能力，碱性彗星分析表明，在用光活化MB处理后，诱导的DNA链断裂量明显更高。这些细胞与野生型细胞相比。光活化MB处理后，所有XPD突变的细胞均表现出强S / G2阻滞和持续的γ-H2AX染色。两者合计，这些结果表明XPD参与了氧化还原过程诱导的病变的修复，并且XPD突变导致对氧化诱导的损伤的反应有所不同。