title: DNA polymerase theta contributes to the generation of C/G mutations during somatic hypermutation of Ig genes.
abstract: Somatic hypermutation of Ig variable region genes is initiated by activation-induced cytidine deaminase; however, the activity of multiple DNA polymerases is required to ultimately introduce mutations. DNA polymerase eta (Poleta) has been implicated in mutations at A/T, but polymerases involved in C/G mutations have not been identified. We have generated mutant mice expressing DNA polymerase (Pol) specifically devoid of polymerase activity. Compared with WT mice, Polq-inactive (Polq, the gene encoding Pol) mice exhibited a reduced level of serum IgM and IgG1. The mutant mice mounted relatively normal primary and secondary immune responses to a T-dependent antigen, but the production of high-affinity specific antibodies was partially impaired. Analysis of the J(H)4 intronic sequences revealed a slight reduction in the overall mutation frequency in Polq-inactive mice. Remarkably, although mutations at A/T were unaffected, mutations at C/G were significantly decreased, indicating an important, albeit not exclusive, role for Pol activity. The reduction of C/G mutations was particularly focused on the intrinsic somatic hypermutation hotspots and both transitions and transversions were similarly reduced. These findings, together with the recent observation that Pol efficiently catalyzes the bypass of abasic sites, lead us to propose that Pol introduces mutations at C/G by replicating over abasic sites generated via uracil-DNA glycosylase.
authors.affiliation: Laboratories for Antigen Receptor Diversity, Cell Signaling, and Developmental Genetics, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama, Kanagawa 230-0045, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Masuda
authors.forename: Rika
authors.initials: R
authors.lastname: Ouchida
authors.forename: Arata
authors.initials: A
authors.lastname: Takeuchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Koseki
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Kawamura
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Tagawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tokuhisa
authors.forename: Takachika
authors.initials: T
authors.lastname: Azuma
authors.forename: Jiyang
authors.initials: J
authors.lastname: O-Wang
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D003596:Cytosine / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000502:physiology*; D005803:Genes, Immunoglobulin / Q000235:genetics*; D006147:Guanine / Q000378:metabolism; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D027041:Somatic Hypermutation, Immunoglobulin / Q000235:genetics*; D000097462:DNA Polymerase theta
chemical_list: D003596:Cytosine; D004259:DNA-Directed DNA Polymerase; D006147:Guanine; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D000097462:DNA Polymerase theta