Catalytic and non‐catalytic roles of DNA polymerase κ in the protection of human cells against genotoxic stresses

DNA polymerase κ (Pol κ) is a specialized DNA polymerase involved in translesion DNA synthesis. Although its bypass activities across lesions are well characterized in biochemistry, its cellular protective roles against genotoxic insults are still elusive. To better understand the in vivo protective roles, we have established a human cell line deficient in the expression of Pol κ (KO) and another expressing catalytically dead Pol κ (CD), to examine the cytotoxic sensitivity to 11 genotoxins including ultraviolet C light (UV). These cell lines were established in a genetic background of Nalm-6-MSH+, a human lymphoblastic cell line that has high efficiency for gene targeting, and functional p53 and mismatch repair activities. We classified the genotoxins into four groups. Group 1 includes benzo[a]pyrene diolepoxide, mitomycin C, and bleomycin, where the sensitivity was equally higher in KO and CD than in the cell line expressing wild-type Pol κ (WT). Group 2 includes hydrogen peroxide and menadione, where hypersensitivity was observed only in KO. Group 3 includes methyl methanesulfonate and ethyl methanesulfonate, where hypersensitivity was observed only in CD. Group 4 includes UV and three chemicals, where the chemicals exhibited similar cytotoxicity to all three cell lines. The results suggest that Pol κ not only protects cells from genotoxic DNA lesions via DNA polymerase activities, but also contributes to genome integrity by acting as a non-catalytic protein against oxidative damage caused by hydrogen peroxide and menadione. The non-catalytic roles of Pol κ in protection against oxidative damage by hydrogen peroxide are discussed. Environ. Mol. Mutagen. 56:650–662, 2015. © 2015 Wiley Periodicals, Inc.