A switch between DNA polymerases δ and λ promotes error-free bypass of 8-oxo-G lesions

Proc Natl Acad Sci U S A. 2012 Dec 11;109(50):20401-6. doi: 10.1073/pnas.1211532109. Epub 2012 Nov 21.

Abstract

7,8-Dihydro-8-oxoguanine (8-oxo-G) is a highly abundant and mutagenic lesion. Replicative DNA polymerases (pols) are slowed down at 8-oxo-G and insert both correct cytosine (C) and incorrect adenine (A) opposite 8-oxo-G, but they preferentially extend A:8-oxo-G mispairs. Nevertheless, 8-oxo-G bypass is fairly accurate in vivo. Thus, the question how correct bypass of 8-oxo-G lesions is accomplished despite the poor extension of C:8-oxo-G base pairs by replicative pols remains unanswered. Here we show that replicative pol δ pauses in front of 8-oxo-G and displays difficulties extending from correct C:8-oxo-G in contrast to extension from incorrect A:8-oxo-G. This leads to stalling of pol δ at 8-oxo-G after incorporation of correct C. This stalling at C:8-oxo-G can be overcome by a switch from pol δ to pols λ, β, or η, all of which are able to assist pol δ in 8-oxo-G bypass by translesion synthesis (TLS). Importantly, however, only pol λ selectively catalyzes the correct TLS past 8-oxo-G, whereas pols β and η show no selectivity and even preferentially enhance incorrect TLS. The selectivity of pol λ to promote the correct bypass depends on its N-terminal domain. Furthermore, pol λ(-/-) mouse embryonic fibroblast extracts display reduced 8-oxo-G TLS. Finally, the correct bypass of 8-oxo-G in gapped plasmids in mouse embryonic fibroblasts and HeLa cells is promoted in the presence of pol λ. Our findings suggest that even though 8-oxo-G is not a blocking lesion per se, correct replication over 8-oxo-G is promoted by a pol switch between pols δ and λ.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cells, Cultured
  • DNA / chemistry
  • DNA / genetics
  • DNA / metabolism
  • DNA Polymerase III / antagonists & inhibitors
  • DNA Polymerase III / deficiency
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism*
  • DNA Polymerase beta / antagonists & inhibitors
  • DNA Polymerase beta / deficiency
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / metabolism*
  • DNA Repair / physiology
  • DNA Replication / physiology
  • Guanine / analogs & derivatives*
  • Guanine / metabolism
  • HeLa Cells
  • Humans
  • Mice
  • Mice, Knockout
  • RNA, Small Interfering / genetics

Substances

  • RNA, Small Interfering
  • 8-hydroxyguanine
  • Guanine
  • DNA
  • DNA polymerase beta2
  • DNA Polymerase III
  • DNA Polymerase beta