DNA polymerase θ contributes to the generation of C/G mutations during somatic hypermutation of Ig genes

Keiji Masuda, Rika Ouchida, Arata Takeuchi, Takashi Saito, Haruhiko Koseki, Kiyoko Kawamura, Masatoshi Tagawa, Takeshi Tokuhisa, Takachika Azuma, Jiyang O-Wang

Research output: Contribution to journalArticlepeer-review

90 Citations (Scopus)

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 η (Polη) 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 (Polθ) specifically devoid of polymerase activity. Compared with WT mice, Polq-inactive (Polq, the gene encoding Polθ) 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 JH4 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 Polθ 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 Polθ efficiently catalyzes the bypass of abasic sites, lead us to propose that Polθ introduces mutations at C/G by replicating over abasic sites generated via uracil-DNA glycosylase.

Original languageEnglish
Pages (from-to)13986-13991
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number39
DOIs
Publication statusPublished - Sep 27 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

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