DNA polymerase ζ generates tandem mutations in immunoglobulin variable regions

J Exp Med. 2012 Jun 4;209(6):1075-81. doi: 10.1084/jem.20112234. Epub 2012 May 21.

Abstract

Low-fidelity DNA polymerases introduce nucleotide substitutions in immunoglobulin variable regions during somatic hypermutation. Although DNA polymerase (pol) η is the major low-fidelity polymerase, other DNA polymerases may also contribute. Existing data are contradictory as to whether pol ζ is involved. We reasoned that the presence of pol η may mask the contribution of pol ζ, and therefore we generated mice deficient for pol η and heterozygous for pol ζ. The frequency and spectra of hypermutation was unaltered between Polζ(+/-) Polη(-/-) and Polζ(+/+) Polη(-/-) clones. However, there was a decrease in tandem double-base substitutions in Polζ(+/-) Polη(-/-) cells compared with Polζ(+/+) Polη(-/-) cells, suggesting that pol ζ generates tandem mutations. Contiguous mutations are consistent with the biochemical property of pol ζ to extend a mismatch with a second mutation. The presence of this unique signature implies that pol ζ contributes to mutational synthesis in vivo. Additionally, data on tandem mutations from wild type, Polζ(+/-), Polζ(-/-), Ung(-/-), Msh2(-/-), Msh6(-/-), and Ung(-/-) Msh2(-/-) clones suggest that pol ζ may function in the MSH2-MSH6 pathway.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Cell Division / genetics
  • DNA Mismatch Repair / genetics
  • DNA-Binding Proteins / genetics
  • DNA-Directed DNA Polymerase / genetics*
  • DNA-Directed DNA Polymerase / metabolism
  • Heterozygote
  • Immunoglobulin Variable Region / genetics*
  • Mice
  • Mice, Mutant Strains
  • MutS Homolog 2 Protein / genetics
  • Mutation*
  • Somatic Hypermutation, Immunoglobulin
  • Uracil-DNA Glycosidase / genetics

Substances

  • DNA-Binding Proteins
  • Immunoglobulin Variable Region
  • Msh6 protein, mouse
  • DNA polymerase zeta
  • Rev3 protein, mouse
  • DNA-Directed DNA Polymerase
  • Rad30 protein
  • Uracil-DNA Glycosidase
  • Msh2 protein, mouse
  • MutS Homolog 2 Protein