Analysis of mice deficient in both REV1 catalytic activity and POLH reveals an unexpected role for POLH in the generation of C to G and G to C transversions during Ig gene hypermutation

Int Immunol. 2012 Mar;24(3):169-74. doi: 10.1093/intimm/dxr109. Epub 2012 Jan 5.

Abstract

Multiple DNA polymerases are involved in the generation of somatic mutations during Ig gene hypermutation. Mice expressing a catalytically inactive REV1 (REV1AA) exhibit reduction of both C to G and G to C transversions and moderate decrease of A/T mutations, whereas DNA polymerase η (POLH) deficiency causes greatly reduced A/T mutations. To investigate whether REV1 and POLH interact genetically and functionally during Ig gene hypermutation, we established REV1AA Polh(-/-) mice and analyzed Ig gene hypermutation in the germinal center (GC) B cells. REV1AA Polh(-/-) mice were born at the expected ratio and developed normally with no apparent gross abnormalities. B-cell development, maturation, Ig gene class switch and the GC B-cell expansion were not affected in these mice. REV1AA Polh(-/-) B cells also exhibited relatively normal sensitivity to etoposide and ionizing radiation. Analysis of somatic mutations in the J(H)4 intronic region revealed that REV1AA Polh(-/-) mice had a further decrease of overall mutation frequency compared with REV1AA or Polh(-/-) mice, indicating that the double deficiency additively affected the generation of mutations. Remarkably, REV1AA Polh(-/-) mice had nearly absent C to G and G to C transversions, suggesting that POLH is essential for the generation of residual C to G and G to C transversions observed in REV1AA mice. These results reveal genetic interactions between REV1 catalytic activity and POLH and identify an alternative pathway, mediated by non-catalytic REV1 and POLH, in the generation of C to G and G to C transversions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • B-Lymphocytes / enzymology
  • B-Lymphocytes / immunology*
  • Biocatalysis*
  • DNA-Directed DNA Polymerase / deficiency*
  • Flow Cytometry
  • Germinal Center / enzymology
  • Germinal Center / immunology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nucleotidyltransferases / deficiency*
  • Somatic Hypermutation, Immunoglobulin / genetics*

Substances

  • Nucleotidyltransferases
  • DNA-Directed DNA Polymerase
  • Rad30 protein
  • Rev1 protein, mouse