DNA polymerase eta is a limiting factor for A:T mutations in Ig genes and contributes to antibody affinity maturation.
DNA polymerase eta (POLH) is required for the generation of A:T mutations during the somatic hypermutation of Ig genes in germinal center B cells. It remains unclear, however, whether POLH is a limiting factor for A:T mutations and how the absence of POLH might affect antibody affinity maturation. We found that the heterozygous Polh+/- mice exhibited a significant reduction in the frequency of A:T mutations in Ig genes, with each type of base substitutions at a level intermediate between the Polh+/+ and Polh(-/-) mice. These observations suggest that Polh is haplo-insufficient for the induction of A:T mutations in Ig genes. Intriguingly, there was also a reduction of C to T and G to A transitions in Polh+/- mice as compared with WT mice. Polh(-/-) mice produced decreased serum titers of high-affinity antibodies against a T-dependent antigen, which was associated with a significant reduction in the number of plasma cells secreting high-affinity antibodies. Analysis of the V region revealed that aa substitutions caused by A:T mutations were greatly reduced in Polh(-/-) mice. These results demonstrate that POLH is a limiting factor for A:T mutations and contributes to the efficient diversification of Ig genes and affinity maturation of antibodies.
Masuda
Keiji
K
Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama, Japan.
Ouchida
Rika
R
Yokoi
Masayuki
M
Hanaoka
Fumio
F
Azuma
Takachika
T
Wang
Ji-Yang
JY
D019943:Amino Acid Substitution; D000818:Animals; D000906:Antibodies / Q000097:blood / Q000276:immunology*; D000915:Antibody Affinity; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D005803:Genes, Immunoglobulin; D051379:Mice; D008817:Mice, Mutant Strains; D009154:Mutation; D010950:Plasma Cells / Q000276:immunology; D027041:Somatic Hypermutation, Immunoglobulin; D000099270:Y-Family DNA Polymerases
D000906:Antibodies; D004259:DNA-Directed DNA Polymerase; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases