DNA Polymerases β and λ Mediate Overlapping and Independent Roles in Base Excision Repair in Mouse Embryonic Fibroblasts

Abstract

Base excision repair (BER) is a DNA repair pathway designed to correct small base lesions in genomic DNA. While DNA polymerase beta (pol β) 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 λ), was shown to be important in BER of oxidative DNA damage. To further explore roles of the X-family DNA polymerases λ and β in BER, we prepared a mouse embryonic fibroblast cell line with deletions in the genes for both pol β and pol λ. Neutral red viability assays demonstrated that pol λ and pol β double null cells were hypersensitive to alkylating and oxidizing DNA damaging agents. In vitro BER assays revealed a modest contribution of pol λ to single-nucleotide BER of base lesions. Additionally, using co-immunoprecipitation experiments with purified enzymes and whole cell extracts, we found that both pol λ and pol β 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.

Screening of Mammalian DNA Polymerase Inhibitors from Rosemary Leaves and Analysis of the Anti-inflammatory and Antiallergic Effects of the Isolated Compounds

“…Pol λ is implicated in V(D)J recombination (Nick McElhinny et al, 2005), translesion synthesis (Maga et al, 2007), and BER (Markkanen et al, 2012). Moreover, studies with eukaryotic cells and reactive oxygen species indicate that pol λ functions as a backup for pol β in BER (Braithwaite et al, 2010) and protects cells from oxidative damage (Zucca et al, 2013).…”

DNA polymerases in nonhomologous end joining: Are there any benefits to standing out from the crowd?

“…Pol k acts as a backup for Pol b function in general BER [Braithwaite et al, 2005;Tano et al, 2007;Braithwaite et al, 2010], but has a specific role in BER of the oxidized base 8-oxo-deoxyguanine (8-oxoG). Together with cofactors replication protein A and proliferating cell nuclear antigen, Pol k is the mammalian polymerase most able to correctly incorporate dC opposite 8-oxoG [Maga et al, 2007].…”

Mouse models of DNA polymerases

“…Single base oxidative and methyl damage is repaired by the base excision repair (BER) pathway. The main polymerases operating during BER are Pol ß, Pol g, and Pol k [Hubscher et al, 1979;Braithwaite et al, 2010]. Adducts that distort the DNA helix are removed by the nucleotide excision repair (NER) pathway.…”