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.
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.
Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
Chie
C
Kano
Fumio
F
Hanaoka
Ji-Yang
JY
Wang
D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology*; D055162:Biocatalysis; D004259:DNA-Directed DNA Polymerase / Q000172:deficiency*; D005434:Flow Cytometry; D018858:Germinal Center / Q000201:enzymology / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009713:Nucleotidyltransferases / Q000172:deficiency*; D027041:Somatic Hypermutation, Immunoglobulin / Q000235:genetics*; D000099270:Y-Family DNA Polymerases
D004259:DNA-Directed DNA Polymerase; D009713:Nucleotidyltransferases; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases; C496086:Rev1 protein, mouse