J Exp Med. 2016 Jul 25. pii: jem.20151227.
Maul, RW; MacCarthy, T; Frank, EG; Donigan, KA; McLenigan, MP; Yang, W; Saribasak, H; Huston, DE; Lange, SS; Woodgate, R; Gearhart, PJ
National Institute on Aging, National Institutes of Health, Baltimore, MD 21224. State University of New York, Stony Brook, NY 11794. National Institute of Child Health and Human Development, National Institutes of Health, Rockville, MD 20850. University of Texas MD Anderson Cancer Center Science Park, Smithville, TX 78957.
DNA polymerase ι (Pol ι) is an attractive candidate for somatic hypermutation in antibody genes because of its low fidelity. To identify a role for Pol ι, we analyzed mutations in two strains of mice with deficiencies in the enzyme: 129 mice with negligible expression of truncated Pol ι, and knock-in mice that express full-length Pol ι that is catalytically inactive. Both strains had normal frequencies and spectra of mutations in the variable region, indicating that loss of Pol ι did not change overall mutagenesis. We next examined if Pol ι affected tandem mutations generated by another error-prone polymerase, Pol ζ. The frequency of contiguous mutations was analyzed using a novel computational model to determine if they occur during a single DNA transaction or during two independent events. Analyses of 2,000 mutations from both strains indicated that Pol ι-compromised mice lost the tandem signature, whereas C57BL/6 mice accumulated significant amounts of double mutations. The results support a model where Pol ι occasionally accesses the replication fork to generate a first mutation, and Pol ζ extends the mismatch with a second mutation.
The team at Ozgene has over two decades of experience creating customised knockout and knock-in mice for pivotal medical research globally. Over 400 scientific publications are based on research using Ozgene mice.