DNA polymerases beta and lambda mediate overlapping and independent roles in base excision repair in mouse embryonic fibroblasts

Base excision repair (BER) is a DNA repair pathway designed to correct small base lesions in genomic DNA. While DNA polymerase beta (pol b) is known to be the main polymerase in the BER pathway, various studies have implicated other DNA polymerases in back-up roles. One such polymerase, DNA polymerase lambda (pol l), was shown to be important in BER of oxidative DNA damage. To further explore roles of the X-family DNA polymerases l and b in BER, we prepared a mouse embryonic fibroblast cell line with deletions in the genes for both pol b and pol l. Neutral red viability assays demonstrated that pol l and pol b double null cells were hypersensitive to alkylating and oxidizing DNA damaging agents. In vitro BER assays revealed a modest contribution of pol l to single-nucleotide BER of base lesions. Additionally, using coimmunoprecipitation experiments with purified enzymes and whole cell extracts, we found that both pol l and pol b interact with the upstream DNA glycosylases for repair of alkylated and oxidized DNA bases. Such interactions could be important in coordinating roles of these polymerases during BER. Citation: Braithwaite EK, Kedar PS, Stumpo DJ, Bertocci B, Freedman JH, et al. (2010) DNA Polymerases b and l Mediate Overlapping and Independent Roles in Base Excision Repair in Mouse Embryonic Fibroblasts. PLoS ONE 5(8): e12229. doi:10.1371/journal.pone.0012229 Editor: Janine Santos, University of Medicine and Dentistry of New Jersey, United States of America Received April 29, 2010; Accepted July 20, 2010; Published August 18, 2010 This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. Funding: This work was supported by National Institutes of Health (NIH) grants ES050158 and ES050159 from the Intramural Research Program and by NIH grant CA055042 (to L.S.). P.K.’s contribution was supported in whole with funds from NIH, under delivery order HHSN273200700046U to Constella/SRA, LLC. 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] . These authors contributed equally to this work.