In vivo evidence for translesion synthesis by the replicative DNA polymerase ?.

ABSTRACT: The intolerance of DNA polymerase ? (Pol?) to incorrect base pairing contributes to its extremely high accuracy during replication, but is believed to inhibit translesion synthesis (TLS). However, chicken DT40 cells lacking the POLD3 subunit of Pol? are deficient in TLS. Previous genetic and biochemical analysis showed that POLD3 may promote lesion bypass by Pol? itself independently of the translesion polymerase Pol? of which POLD3 is also a subunit. To test this hypothesis, we have inactivated Pol? proofreading in pold3 cells. This significantly restored TLS in pold3 mutants, enhancing dA incorporation opposite abasic sites. Purified proofreading-deficient human Pol? holoenzyme performs TLS of abasic sites in vitro much more efficiently than the wild type enzyme, with over 90% of TLS events resulting in dA incorporation. Furthermore, proofreading deficiency enhances the capability of Pol? to continue DNA synthesis over UV lesions both in vivo and in vitro These data support Pol? contributing to TLS in vivo and suggest that the mutagenesis resulting from loss of Pol? proofreading activity may in part be explained by enhanced lesion bypass.

SUBMITTER: Hirota K 

PROVIDER: S-EPMC5009730 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature