DNA polymerase ζ (Pol ζ) is a specialized Pol that is involved in translesion DNA synthesis (TLS), in particular, in the extension of primer DNA after bypassing DNA lesions. Previously, we established human cells that express a variant form of Pol ζ with an amino acid change of leucine 2618 to methionine (L2618M) in the catalytic subunit REV3L (DNA Repair, 45, 34–43, 2016). This amino acid change made the cells more sensitive to the mutagenicity of benzo[a]pyrene diol epoxide (BPDE). In this study, we embedded BPDE-N²-guanine at a defined position in the supF gene on the shuttle plasmid and introduced it to REV3 L2618M cells or the wild-type (WT) cells to examine how far Pol ζ L2618M extends the primer DNA after bypassing the lesion. The adduct induced primarily G to T and G to C at the adducted site in both cell lines, but generated additional sequence changes such as base substitutions, deletions and additions in the extension patch much more often in REV3 L2618M cells than in the WT cells. Mutations in the extension patch in REV3 L2618M cells occurred most often within 10 bps from the adducted site. Then, the number of mutations gradually decreased and no mutations were observed between 30 and 40 bps from the lesion. We concluded that human Pol ζ L2618M and perhaps WT Pol ζ extend the primer DNA up to approximately 30 bps from the lesion in vivo. The possibility of involvement of Pol ζ L2618M in the insertion step of TLS is discussed.

DNA 聚合酶 ζ (Pol ζ) 是一种特殊的 Pol，它参与跨损伤 DNA 合成 (TLS)，特别是在绕过 DNA 损伤后引物 DNA 的延伸。之前，我们建立了表达 Pol ζ 变体形式的人类细胞，其中催化亚基 REV3L 中的亮氨酸 2618 氨基酸变为甲硫氨酸 (L2618M) (DNA Repair, 45, 34–43, 2016)。这种氨基酸变化使细胞对苯并[ a ]芘二醇环氧化物（BPDE）的致突变性更加敏感。在这项研究中，我们将 BPDE- N ^{2 -}鸟嘌呤嵌入到supF穿梭质粒上的基因并将其引入 REV3 L2618M 细胞或野生型 (WT) 细胞，以检查绕过病变后 Pol ζ L2618M 延伸引物 DNA 的程度。在两种细胞系中，加合物主要在加合物位点诱导 G 到 T 和 G 到 C，但在 REV3 L2618M 细胞中比在 WT 细胞中更频繁地产生额外的序列变化，例如碱基替换、缺失和延伸补丁中的添加。REV3 L2618M 细胞中扩展补丁中的突变最常发生在距加合物位点 10 bps 以内。然后，突变的数量逐渐减少，并且在距病灶 30 到 40 bps 之间没有观察到突变。我们得出的结论是，人类 Pol ζ L2618M 和 WT Pol ζ 可能将引物 DNA 延伸至距体内病变约 30 bps。