Simultaneous Disruption of Two DNA Polymerases, Polg and Polf, in Avian DT40 Cells Unmasks the Role of Polg in Cellular Response to Various DNA Lesions

Replicative DNA polymerases are frequently stalled by DNA lesions. The resulting replication blockage is released by homologous recombination (HR) and translesion DNA synthesis (TLS). TLS employs specialized TLS polymerases to bypass DNA lesions. We provide striking in vivo evidence of the cooperation between DNA polymerase g, which is mutated in the variant form of the cancer predisposition disorder xeroderma pigmentosum (XP-V), and DNA polymerase f by generating POLg/POLf cells from the chicken DT40 cell line. POLf cells are hypersensitive to a very wide range of DNA damaging agents, whereas XP-V cells exhibit moderate sensitivity to ultraviolet light (UV) only in the presence of caffeine treatment and exhibit no significant sensitivity to any other damaging agents. It is therefore widely believed that Polg plays a very specific role in cellular tolerance to UV-induced DNA damage. The evidence we present challenges this assumption. The phenotypic analysis of POLg/POLf cells shows that, unexpectedly, the loss of Polg significantly rescued all mutant phenotypes of POLf cells and results in the restoration of the DNA damage tolerance by a backup pathway including HR. Taken together, Polg contributes to a much wide range of TLS events than had been predicted by the phenotype of XP-V cells. Citation: Hirota K, Sonoda E, Kawamoto T, Motegi A, Masutani C, et al. (2010) Simultaneous Disruption of Two DNA Polymerases, Polg and Polf, in Avian DT40 Cells Unmasks the Role of Polg in Cellular Response to Various DNA Lesions. PLoS Genet 6(10): e1001151. doi:10.1371/journal.pgen.1001151 Editor: James E. Haber, Brandeis University, United States of America Received March 15, 2010; Accepted September 8, 2010; Published October 7, 2010 Copyright: 2010 Hirota et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Financial support was provided in part by the Program for Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN) (to ST) and by grants from the Fujiwara Foundation of Science, the Uehara Memorial Foundation, and the Naito Foundation (to KH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected] ¤ Current address: Department of Life Science, Faculty of Science, Gakushuin University, Tokyo, Japan