title: The interaction between AID and CIB1 is nonessential for antibody gene diversification by gene conversion or class switch recombination.
abstract: Activation-induced deaminase (AID) initiates somatic hypermutation, gene conversion and class switch recombination by deaminating variable and switch region DNA cytidines to uridines. AID is predominantly cytoplasmic and must enter the nuclear compartment to initiate these distinct antibody gene diversification reactions. Nuclear AID is relatively short-lived, as it is efficiently exported by a CRM1-dependent mechanism and it is susceptible to proteasome-dependent degradation. To help shed light on mechanisms of post-translational regulation, a yeast-based screen was performed to identify AID-interacting proteins. The calcium and integrin binding protein CIB1 was identified by sequencing and the interaction was confirmed by immunoprecipitation experiments. The AID/CIB1 resisted DNase and RNase treatment, and it is therefore unlikely to be mediated by nucleic acid. The requirement for CIB1 in AID-mediated antibody gene diversification reactions was assessed in CIB1-deficient DT40 cells and in knockout mice, but immunoglobulin gene conversion and class switch recombination appeared normal. The DT40 system was also used to show that CIB1 over-expression has no effect on gene conversion and that AID-EGFP subcellular localization is normal. These combined data demonstrate that CIB1 is not required for AID to mediate antibody gene diversification processes. It remains possible that CIB1 has an alternative, a redundant or a subtle non-limiting regulatory role in AID biology.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Beckman Center for Genome Engineering, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Zachary L
authors.initials: ZL
authors.lastname: Demorest
authors.forename: Donna A
authors.initials: DA
authors.lastname: MacDuff
authors.forename: William L
authors.initials: WL
authors.lastname: Brown
authors.forename: Scott G
authors.initials: SG
authors.lastname: Morham
authors.forename: Leslie V
authors.initials: LV
authors.lastname: Parise
authors.forename: Reuben S
authors.initials: RS
authors.lastname: Harris
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism*; D005785:Gene Conversion / Q000235:genetics*; D006801:Humans; D017578:Immunoglobulin Class Switching; D007136:Immunoglobulins / Q000235:genetics*; D047468:Immunoprecipitation; D051379:Mice; D018345:Mice, Knockout; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: C109198:CIB1 protein, human; D002135:Calcium-Binding Proteins; D007136:Immunoglobulins; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase