Chaim Isaac A, Gardner Alycia, Wu Jie, Iyama Teruaki, Wilson David M, Samson Leona D
Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Nucleic Acids Res. 2017 Apr 7;45(6):3242-3252. doi: 10.1093/nar/gkx015.
Etheno (ε) DNA base adducts are highly mutagenic lesions produced endogenously via reactions with lipid peroxidation (LPO) products. Cancer-promoting conditions, such as inflammation, can induce persistent oxidative stress and increased LPO, resulting in the accumulation of ε-adducts in different tissues. Using a recently described fluorescence multiplexed host cell reactivation assay, we show that a plasmid reporter bearing a site-specific 3,N4-ethenocytosine (εC) causes transcriptional blockage. Notably, this blockage is exacerbated in Cockayne Syndrome and xeroderma pigmentosum patient-derived lymphoblastoid and fibroblast cells. Parallel RNA-Seq expression analysis of the plasmid reporter identifies novel transcriptional mutagenesis properties of εC. Our studies reveal that beyond the known pathways, such as base excision repair, the process of transcription-coupled nucleotide excision repair plays a role in the removal of εC from the genome, and thus in the protection of cells and tissues from collateral damage induced by inflammatory responses.
乙烯基（ε）DNA碱基加合物是通过与脂质过氧化（LPO）产物发生反应而内源性产生的高度致突变性损伤。诸如炎症等促癌条件可诱导持续性氧化应激并增加LPO，导致ε-加合物在不同组织中积累。使用最近描述的荧光多重宿主细胞再激活试验，我们发现携带位点特异性3,N4-乙烯基胞嘧啶（εC）的质粒报告基因会导致转录阻滞。值得注意的是，在科凯恩综合征和着色性干皮病患者来源的淋巴母细胞和成纤维细胞中，这种阻滞会加剧。对该质粒报告基因进行的平行RNA测序表达分析确定了εC的新型转录诱变特性。我们的研究表明，除了碱基切除修复等已知途径外，转录偶联核苷酸切除修复过程在从基因组中去除εC方面发挥作用，从而保护细胞和组织免受炎症反应诱导的附带损伤。
