title: Attracting AID to targets of somatic hypermutation.
abstract: The process of somatic hypermutation (SHM) of immunoglobulin (Ig) genes requires activation-induced cytidine deaminase (AID). Although mistargeting of AID is detrimental to genome integrity, the mechanism and the cis-elements responsible for targeting of AID are largely unknown. We show that three CAGGTG cis-elements in the context of Ig enhancers are sufficient to target SHM to a nearby transcribed gene. The CAGGTG motif binds E47 in nuclear extracts of the mutating cells. Replacing CAGGTG with AAGGTG in the construct without any other E47 binding site eliminates SHM. The CA versus AA effect requires AID. CAGGTG does not enhance transcription, chromatin acetylation, or overall target gene activity. The other cis-elements of Ig enhancers alone cannot attract the SHM machinery. Collectively with other recent findings, we postulate that AID targets all genes expressed in mutating B cells that are associated with CAGGTG motifs in the appropriate context. Ig genes are the most highly mutated genes, presumably because of multiple CAGGTG motifs within the Ig genes, high transcription activity, and the presence of other cooperating elements in Ig enhancers.
authors.affiliation: Committee on Immunology, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tanaka
authors.forename: Hong Ming
authors.initials: HM
authors.lastname: Shen
authors.forename: Sarayu
authors.initials: S
authors.lastname: Ratnam
authors.forename: Prashant
authors.initials: P
authors.lastname: Kodgire
authors.forename: Ursula
authors.initials: U
authors.lastname: Storb
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D004789:Enzyme Activation; D005803:Genes, Immunoglobulin; D009154:Mutation; D027041:Somatic Hypermutation, Immunoglobulin; D051820:TCF Transcription Factors / Q000378:metabolism; D058125:Transcription Factor 7-Like 1 Protein; D014158:Transcription, Genetic
chemical_list: D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D003564:Cytidine Deaminase