Document Detail


Hypermutation at A/T sites during G.U mismatch repair in vitro by human B-cell lysates.
MedLine Citation:
PMID:  18786917     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Somatic hypermutation in the variable regions of immunoglobulin genes is required to produce high affinity antibody molecules. Somatic hypermutation results by processing G.U mismatches generated when activation-induced cytidine deaminase (AID) deaminates C to U. Mutations at C/G sites are targeted mainly at deamination sites, whereas mutations at A/T sites entail error-prone DNA gap repair. We used B-cell lysates to analyze salient features of somatic hypermutation with in vitro mutational assays. Tonsil and hypermutating Ramos B-cells convert C-->U in accord with AID motif specificities, whereas HeLa cells do not. Using tonsil cell lysates to repair a G.U mismatch, A/T and G/C targeted mutations occur about equally, whereas Ramos cell lysates make fewer mutations at A/T sites (approximately 24%) compared with G/C sites (approximately 76%). In contrast, mutations in HeLa cell lysates occur almost exclusively at G/C sites (> 95%). By recapitulating two basic features of B-cell-specific somatic hypermutation, G/C mutations targeted to AID hot spot motifs and elevated A/T mutations dependent on error-prone processing of G.U mispairs, these cell free assays provide a practical method to reconstitute error-prone mismatch repair using purified B-cell proteins.
Authors:
Phuong Pham; Ke Zhang; Myron F Goodman
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2008-09-11
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  283     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2008 Nov 
Date Detail:
Created Date:  2008-11-10     Completed Date:  2009-01-07     Revised Date:  2013-06-05    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  31754-62     Citation Subset:  IM    
Affiliation:
Department of Biological Sciences and Chemistry, University of Southern California, Los Angeles, California 90089-2910, USA.
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MeSH Terms
Descriptor/Qualifier:
B-Lymphocytes / metabolism*
Base Sequence
DNA Mismatch Repair / genetics*
Humans
Molecular Sequence Data
Mutation / genetics
Grant Support
ID/Acronym/Agency:
ES013192/ES/NIEHS NIH HHS; R37GM21422/GM/NIGMS NIH HHS
Comments/Corrections

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