DNA polymerase kappa counteracts inflammation‐induced mutagenesis in multiple organs of mice

Abstract

In vitro studies indicate that DNA polymerase kappa (Polκ) is able to accurately and efficiently perform DNA synthesis using templates containing various types of DNA damage, including benzo[a]pyrene (BP)‐induced N2‐deoxyguanosine adducts. In this study, we examined sensitivity of inactivated Polk knock‐in (Polk−/−) mice to BP carcinogenicity in the colon by administering an oral dose of BP plus dextran sulfate sodium (DSS), an inflammation causing promoter of carcinogenesis. Although colon cancer was successfully induced by BP plus DSS, there was no significant difference in tumor incidence or multiplicity between Polk−/− and Polk+/+ mice. Malignant lymphoma was induced in thymus by the treatment only in Polk−/− mice, but it lacked statistical significance. Mutant frequencies (MFs) in the gpt reporter gene were strongly enhanced in colon; almost to the same extent in both types of mice. Micronucleus formation in bone marrow at the high dose of BP and DNA adducts in colon and lung was not significantly different between two types of mice. Surprisingly, however, Polk−/− mice exhibited significantly higher MFs in colon and lung than did Polk+/+ mice when they were treated with DSS alone. The most prominent mutation induced by DSS treatment was G:C to C:G transversion, whose specific MF in proximal colon was 30 times higher in Polk−/− than in Polk+/+ mice. DSS alone did not enhance MF at all in Polk+/+ mice. The results indicate that Polκ does not suppress BP‐induced mutagenesis and carcinogenesis in the colon, but counteracts inflammation‐induced mutagenesis in multiple organs. Environ. Mol. Mutagen. 60:320–330, 2019. © 2019 Wiley Periodicals, Inc.

Mammalian DNA Polymerase Kappa Activity and Specificity

“…Mutagenesis induced by BPDE was elevated in catalytically dead (CD) and knockout (KO) pol κ Nalm-6 cells as well as in mouse embryonic stem cells, confirming the catalytic role of pol κ in suppressing mutations by BPDE [6,11,13,16,92,94]. In mice with wild-type ( polk +/+ ) or a catalytically inactive variant ( polk −/− ) of pol κ, mutagenesis induced by B[a]P was found to be insignificant in the colon, although spontaneous mutation frequency increased significantly in polk −/− mice at old age [95,96,97]. Thus, pol κ appears to catalyze TLS across endogenously generated DNA adducts caused by oxidative damage and alkylating agents in an error-free manner.…”

“…Thus, pol κ appears to catalyze TLS across endogenously generated DNA adducts caused by oxidative damage and alkylating agents in an error-free manner. Hakura et al showed that B[a]P was not carcinogenic in mice when delivered alone [96]. Mice exposed simultaneously to B[a]P and dextran sulfate sodium (DSS), which causes inflammation in the colon, developed tumors.…”

Impact of G-Quadruplexes and Chronic Inflammation on Genome Instability: Additive Effects during Carcinogenesis

“…Hakura, et al treated pol κ −/− and pol κ +/+ mice with either the mutagen benzo(a)pyrene (BP), DSS, or both. There was no significant difference in the incidence of tumor development between pol κ −/− and pol κ +/+ mice when treated with both BP and DSS, suggesting that pol κ does not function to repress tumorigenesis [95]. However, using a gpt transgene reporter, the authors showed that DSS treatment alone increased mutagenesis in pol κ −/− mice, and not in pol κ +/+ mice, with G > C transversions being the most frequent errors in both the distal colon and lungs of these mice [95].…”

“…There was no significant difference in the incidence of tumor development between pol κ −/− and pol κ +/+ mice when treated with both BP and DSS, suggesting that pol κ does not function to repress tumorigenesis [95]. However, using a gpt transgene reporter, the authors showed that DSS treatment alone increased mutagenesis in pol κ −/− mice, and not in pol κ +/+ mice, with G > C transversions being the most frequent errors in both the distal colon and lungs of these mice [95]. Taken together, pol κ may display lower fidelity during 8oxoG TLS, but the described in vivo study suggests it does play a role in suppressing mutagenesis in an oxidative stress environment.…”

Targeting translesion synthesis (TLS) to expose replication gaps, a unique cancer vulnerability

“…This phenomenon is observed in Rev1 deficient mice, which when crossed to skin-cancer prone mice, exhibit inflammatory hyperplasia and an acceleration of skin cancer [113]. Of note, pol κ deficient mice have increased inflammationmediated mutagenesis, and pol ζ deficient cells exhibit chromosomal breaks and increased sensitivity to nitric oxide, a mediator of inflammatory responses [114,115]. Thus, TLS can potentially alleviate inflammation-mediated DNA lesions and help mitigate stress responses [116][117][118].…”