Regulation of hypermutation by activation-induced cytidine deaminase phosphorylation.
Activation-induced cytidine deaminase (AID) initiates Ig class switch recombination and somatic hypermutation by producing U:G mismatches in DNA. These mismatches also have the potential to induce DNA damage including double-stranded breaks and chromosome translocations; therefore, strict regulation of AID is important for maintaining genomic stability. In addition to transcriptional regulation, it has been proposed that phosphorylation can also modulate AID activity. Using a combination of MS and immunochemical approaches we found that 5-15% of the AID expressed in activated B cells was phosphorylated at serine-38 (p38AID). This form of AID was enriched in the chromatin fraction in activated B cells, suggesting a role for phosphorylation in targeting AID to DNA. Consistent with this idea, serine-38 to alanine mutant AID (AID(S38A)) showed diminished somatic hypermutation activity on artificial and physiological DNA targets. We conclude that a small fraction of AID is phosphorylated in activated B cells and that the modified form contributes disproportionately to hypermutation.
McBride
Kevin M
KM
Laboratory of Molecular Immunology and Laboratory of Mass Spectrometry, The Rockefeller University and Howard Hughes Medical Institute, New York, NY 10021, USA.
Gazumyan
Anna
A
Woo
Eileen M
EM
Barreto
Vasco M
VM
Robbiani
Davide F
DF
Chait
Brian T
BT
Nussenzweig
Michel C
MC
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology; D002478:Cells, Cultured; D003564:Cytidine Deaminase / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D005347:Fibroblasts / Q000201:enzymology; D017578:Immunoglobulin Class Switching / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D027041:Somatic Hypermutation, Immunoglobulin / Q000235:genetics*; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
D010768:Phosphoserine; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase