title: AID recruits UNG and Msh2 to Ig switch regions dependent upon the AID C terminus [corrected].
abstract: Activation-induced cytidine deaminase (AID) is induced in B cells during an immune response and is essential for both class-switch recombination (CSR) and somatic hypermutation of Ab genes. The C-terminal 10 aa of AID are required for CSR but not for somatic hypermutation, although their role in CSR is unknown. Using retroviral transduction into mouse splenic B cells, we show that the C terminus is not required for switch (S) region double-strand breaks (DSBs) and therefore functions downstream of DSBs. Using chromatin immunoprecipitation, we show that AID binds cooperatively with UNG and the mismatch repair proteins Msh2-Msh6 to Ig Sμ and Sγ3 regions, and this depends on the C terminus and the deaminase activity of AID. We also show that mismatch repair does not contribute to the efficiency of CSR in the absence of the AID C terminus. Although it has been demonstrated that both UNG and Msh2-Msh6 are important for introduction of S region DSBs, our data suggest that the ability of AID to recruit these proteins is important for DSB resolution, perhaps by directing the S region DSBs toward accurate and efficient CSR via nonhomologous end joining.
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01655, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Ranjit
authors.forename: Lyne
authors.initials: L
authors.lastname: Khair
authors.forename: Erin K
authors.initials: EK
authors.lastname: Linehan
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Ucher
authors.forename: Mrinmay
authors.initials: M
authors.lastname: Chakrabarti
authors.forename: Carol E
authors.initials: CE
authors.lastname: Schrader
authors.forename: Janet
authors.initials: J
authors.lastname: Stavnezer
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002469:Cell Separation; D047369:Chromatin Immunoprecipitation; D003564:Cytidine Deaminase / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005434:Flow Cytometry; D017578:Immunoglobulin Class Switching / Q000502:physiology*; D007074:Immunoglobulin G; D007134:Immunoglobulin Switch Region / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051718:MutS Homolog 2 Protein / Q000378:metabolism*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051981:Uracil-DNA Glycosidase / Q000378:metabolism*; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D004268:DNA-Binding Proteins; D007074:Immunoglobulin G; C102997:Msh6 protein, mouse; D051981:Uracil-DNA Glycosidase; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase; C497173:Msh2 protein, mouse; D051718:MutS Homolog 2 Protein