Ji Debin, You Changjun, Wang Pengcheng, Wang Yinsheng
Department of Chemistry, University of California , Riverside, California 92521, United States.
Chem Res Toxicol. 2014 Jul 21;27(7):1304-9. doi: 10.1021/tx500169u. Epub 2014 Jul 10.
Recently 5-hydroxymethyl-2'-deoxycytidine (5hmdC), 5-formyl-2'-deoxycytidine (5fdC), and 5-carboxyl-2'-deoxycytidine (5cadC) were discovered in mammalian DNA as oxidation products of 5-methyl-2'-deoxycytidine (5mdC) induced by the ten-eleven translocation family of enzymes. These oxidized derivatives of 5mdC may not only act as intermediates of active cytosine demethylation in mammals but also serve as epigenetic marks on their own. It remains unclear how 5hmdC, 5fdC, and 5cadC affect DNA replication in mammalian cells. Here, we examined the effects of the three modified nucleosides on the efficiency and accuracy of DNA replication in HEK293T human kidney epithelial cells. Our results demonstrated that a single, site-specifically incorporated 5fdC or 5cadC conferred modest drops, by approximately 30%, in replication bypass efficiency without inducing detectable mutations in human cells, whereas replicative bypass of 5hmdC is both accurate and efficient. The lack of pronounced perturbation of these oxidized 5mdC derivatives on DNA replication is consistent with their roles in epigenetic regulation of gene expression.
最近，5-羟甲基-2'-脱氧胞苷（5hmdC）、5-甲酰基-2'-脱氧胞苷（5fdC）和5-羧基-2'-脱氧胞苷（5cadC）作为由TET蛋白家族诱导的5-甲基-2'-脱氧胞苷（5mdC）的氧化产物，在哺乳动物DNA中被发现。这些5mdC的氧化衍生物不仅可能作为哺乳动物中活性胞嘧啶去甲基化的中间体，还可能自身作为表观遗传标记。目前尚不清楚5hmdC、5fdC和5cadC如何影响哺乳动物细胞中的DNA复制。在此，我们研究了这三种修饰核苷对HEK293T人肾上皮细胞中DNA复制效率和准确性的影响。我们的结果表明，单个位点特异性掺入的5fdC或5cadC使复制绕过效率适度下降约30%，且在人类细胞中未诱导可检测到的突变，而5hmdC的复制绕过既准确又高效。这些氧化的5mdC衍生物对DNA复制缺乏明显干扰，这与它们在基因表达表观遗传调控中的作用一致。
