Single-stranded DNA-specific cytidine deaminase. Involved in somatic hypermutation (SHM), gene conversion, and class-switch recombination (CSR) in B-lymphocytes by deaminating C to U during transcription of Ig-variable (V) and Ig-switch (S) region DNA. Required for several crucial steps of B-cell terminal differentiation necessary for efficient antibody responses (PubMed:18722174, PubMed:21385873, PubMed:21518874, PubMed:27716525). May also play a role in the epigenetic regulation of gene expression by participating in DNA demethylation (PubMed:21496894). a 2'-deoxycytidine in single-stranded DNA + H(+) + H2O = a 2'-deoxyuridine in single-stranded DNA + NH4(+) Interacts with CTNNBL1; the interaction is important for the immunoglobulin switch activity of AICDA (PubMed:18722174, PubMed:21385873). Interacts (via its NLS) with KPNA1. Interacts with PKA/PRKACA and PRKAR1A/PKR1 (PubMed:16387847). Interacts with TRIM28 and NCL (By similarity). Interacts with SUPT6H (PubMed:21518874). Interacts with RNF126 (PubMed:23277564). Directly interacts with MCM3AP; this interaction may favor AICDA recruitment to immunoglobulin variable region genes, hence promoting somatic hypermutations (PubMed:20507984). Predominantly cytoplasmic (PubMed:21385873). In the presence of MCM3AP/GANP, relocalizes to the nucleus (By similarity). Strongly expressed in lymph nodes and tonsils. Negatively regulated by microRNA-155 (miR-155). Ser-38 is the major site whereas Thr-27 is the minor site of phosphorylation. Phosphorylation regulates its class-switch recombination activity. Probably monoubiquitinated on several residues by RNF126. The disease is caused by variants affecting the gene represented in this entry. Belongs to the cytidine and deoxycytidylate deaminase family. AICDA mutation db