DNA polymerase ζ (pol ζ) is involved in translesion replication (translesion synthesis, TLS) and plays an essential role in embryogenesis. In adults, pol ζ triggers mutation as a result of error-prone TLS and causes carcinogenesis. The catalytic subunit of pol ζ, REV3, is evolutionarily conserved from yeast and plants to higher eukaryotes. However, the structures are notably different: unlike that in yeast REV3, a large intermediate domain is inserted in REV3 of humans and mice. The domain is mostly occupied with noncommittal structures (random coil…etc.); therefore, its role and function are yet to be resolved. Previously, we reported deficient levels of ultraviolet (UV)-induced TLS in fibroblasts derived from the Rev3-knockout mouse embryo (Rev3KO-MEF). Here, we constructed a mouse Rev3-expressing plasmid with a deleted intermediate domain (532-1793 a.a,) and transfected it into Rev3KO-MEF. The isolated stable transformants showed comparable levels of UV-sensitivity and UV-TLS activity to those in wild-type MEF, detected using an alkaline sucrose density gradient sedimentation. These results indicate that the intermediate domain is nonessential for UV-induced translesion replication in cultured mouse cells.

DNA 聚合酶 ζ (pol ζ) 参与跨损伤复制（跨损伤合成，TLS）并在胚胎发生中发挥重要作用。在成人中，pol ζ 会由于容易出错的 TLS 引发突变并导致致癌作用。pol ζ 的催化亚基 REV3 从酵母和植物到高等真核生物在进化上是保守的。然而，结构明显不同：与酵母 REV3 不同，人类和小鼠的 REV3 中插入​​了一个大的中间结构域。该域主要被不明确的结构（无规卷曲等）占据；因此，它的作用和作用还有待解决。先前，我们报道水平不足紫外线（UV）引起的TLS在从成纤维细胞Rev3型敲除小鼠胚胎（Rev3型KO-MEF）。在这里，我们构建了一个鼠标Rev3表达质粒，中间域缺失 (532-1793 aa)，并将其转染到Rev3 KO-MEF 中。分离的稳定转化体显示出与野生型 MEF 相当的 UV 敏感性和 UV-TLS 活性水平，使用碱性蔗糖密度梯度沉降检测。这些结果表明中间结构域对于培养的小鼠细胞中紫外线诱导的跨损伤复制不是必需的。