Dibromoacetonitrile (DBAN) is a carcinogenic disinfection byproduct (DBP) but how it precipitates cancer is unknown. Nucleotide excision repair (NER) is a versatile repair mechanism for removing bulky DNA lesions to maintain genome stability, and impairment of this process is associated with cancer development. In this study, we found that DBAN inhibited NER and investigated its mechanism with other DNA damage responses. Human keratinocytes HaCaT were treated with DBAN followed by ultraviolet (UV) as a model inducer of DNA damage, pyrimidine dimers, which require NER for the removal. DBAN pretreatment exacerbated UV-cytotoxicity, and inhibited the repair of pyrimidine dimers. DBAN treatment delayed the recruitment of NER proteins, transcription factor IIH (TFIIH) and xeroderma pigmentosum complementation group G (XPG), to DNA damaged sites, and subsequent gap filling process. Moreover, DBAN suppressed the UV-induced double strand breaks (DSBs) formation, as well as phosphorylated histone H2AX (γ-H2AX), a widely used DNA damage marker. Altogether, DBAN could negatively impact the NER process and phosphorylation pathway responding to DNA damage. This study was the first to identify the inhibition of NER and damage response signaling as a genotoxicity mechanism of a class of DBPs and it may serve as a foundation for DBP carcinogenesis.

二溴乙腈 (DBAN) 是一种致癌的消毒副产物 (DBP)，但它如何诱发癌症尚不清楚。核苷酸切除修复 (NER) 是一种通用的修复机制，用于去除大量 DNA 损伤以维持基因组稳定性，并且该过程的损害与癌症发展有关。在这项研究中，我们发现 DBAN 抑制 NER 并研究其与其他 DNA 损伤反应的机制。用 DBAN 处理人类角质形成细胞 HaCaT，然后用紫外线 (UV) 作为 DNA 损伤的模型诱导剂，嘧啶二聚体，需要 NER 才能去除。DBAN 预处理加剧了紫外线的细胞毒性，并抑制了嘧啶二聚体的修复。DBAN 治疗延迟了 NER 蛋白、转录因子 IIH (TFIIH) 和色素性干皮病互补组 G (XPG) 向 DNA 损伤位点的募集，以及随后的间隙填充过程。此外，DBAN 抑制紫外线诱导的双链断裂 (DSB) 形成，以及磷酸化组蛋白 H2AX (γ-H2AX)，这是一种广泛使用的 DNA 损伤标记物。总之，DBAN 会对 NER 过程和响应 DNA 损伤的磷酸化途径产生负面影响。本研究首次将抑制 NER 和损伤反应信号确定为一类 DBP 的遗传毒性机制，并可能作为 DBP 致癌的基础。