DNA polymerases eta and theta function in the same genetic pathway to generate mutations at A/T during somatic hypermutation of Ig genes.
Somatic hypermutation of the Ig genes requires the activity of multiple DNA polymerases to ultimately introduce mutations at both A/T and C/G base pairs. Mice deficient for DNA polymerase eta (POLH) exhibited an approximately 80% reduction of the mutations at A/T, whereas absence of polymerase (POLQ) resulted in approximately 20% reduction of both A/T and C/G mutations. To investigate whether the residual A/T mutations observed in the absence of POLH are generated by POLQ and how these two polymerases might cooperate or compete with each other to generate A/T mutations, here we have established mice deficient for both POLH and POLQ. Polq(-/-)Polh(-/-) mice, however, did not show a further decrease of A/T mutations as compared with Polh(-/-) mice, suggesting that POLH and POLQ function in the same genetic pathway in the generation of these mutations. Frequent misincorporation of nucleotides, in particular opposite template T, is a known feature of POLH, but the efficiency of extension beyond the misincorporation differs significantly depending on the nature of the mispairing. Remarkably, we found that POLQ catalyzed extension more efficiently than POLH from all types of mispaired termini opposite A or T. Moreover, POLQ was able to extend mispaired termini generated by POLH albeit at a relatively low efficiency. These results reveal genetic and biochemical interactions between POLH and POLQ and suggest that POLQ might cooperate with POLH to generate some of the A/T mutations during the somatic hypermutation of Ig genes.
Masuda
Keiji
K
Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama 230-0045, Japan.
Ouchida
Rika
R
Hikida
Masaki
M
Kurosaki
Tomohiro
T
Yokoi
Masayuki
M
Masutani
Chikahide
C
Seki
Mineaki
M
Wood
Richard D
RD
Hanaoka
Fumio
F
O-Wang
Jiyang
J
D000225:Adenine / Q000378:metabolism*; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000502:physiology; D002454:Cell Differentiation; D049109:Cell Proliferation; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D005803:Genes, Immunoglobulin; D017578:Immunoglobulin Class Switching; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D027041:Somatic Hypermutation, Immunoglobulin; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology; D013941:Thymine / Q000378:metabolism*; D000097462:DNA Polymerase theta; D000099270:Y-Family DNA Polymerases
D000225:Adenine; D004259:DNA-Directed DNA Polymerase; D013941:Thymine; D000097462:DNA Polymerase theta; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases