A new proofreading mechanism for lesion bypass by DNA polymerase-γ

Abstract

Replicative DNA polymerases (DNA pols) increase their fidelity by removing misincorporated nucleotides with their 3′→5′ exonuclease activity. Exonuclease activity reduces translesion synthesis (TLS) efficiency and TLS DNA pols lack 3′→5′ exonuclease activity. Here we show that physiological concentrations of pyrophosphate (PP i) activate the pyrophosphorolytic activity by DNA pol-γ, allowing the preferential excision of the incorrectly incorporated A opposite a 7,8-dihydro-8-oxoguanine lesion, or T opposite a 6-methyl-guanine, with respect to the correct C. This is the first example of an alternative proofreading mechanism used during TLS. © 2012 EUROPEAN MOLECULAR BIOLOGY ORGANIZATION.