Activation-Induced Cytidine Deaminase (AICDA) Enzyme

This gene encodes a RNA-editing deaminase that is a member of the cytidine deaminase family. The protein is involved in somatic hypermutation, gene conversion, and class-switch recombination of immunoglobulin genes. Defects in this gene are the cause of autosomal recessive hyper-IgM immunodeficiency syndrome type 2 (HIGM2). [provided by RefSeq, Feb 2009]

Function: Single-stranded DNA-specific cytidine deaminase. Involved in somatic hypermutation, gene conversion, and class-switch recombination in B-lymphocytes. Required for several crucial steps of B-cell terminal differentiation necessary for efficient antibody responses. May also play a role in the epigenetic regulation of gene expression by participating in DNA demethylation. Ref.9 Ref.10 Ref.11 Ref.13

Catalytic activity: Cytosine in single-stranded DNA + H2O = uracil in single-stranded DNA + NH3.

Cofactor: Zinc

By similarity.

Subunit structure: Interacts with CTNNBL1; the interaction is important for the immunoglobulin switch activity of AICDA. Interacts (via its NLS) with KPNA1. Interacts with PKA/PRKACA and PRKAR1A/PKR1. Interacts with TRIM28 and NCL

By similarity. Interacts with SUPT6H. Ref.8 Ref.9 Ref.11 Ref.13

Subcellular location: Nucleus. Cytoplasm. Note: Predominantly cytoplasmic but shuttles between the nucleus and the cytoplasm. Ref.7 Ref.9 Ref.11 Ref.12

Tissue specificity: Strongly expressed in lymph nodes and tonsils.

Post-translational modification: Ser-38 is the major site whereas Thr-27 is the minor site of phosphorylation. Phosphorylation regulates its class-switch recombination activity.

Involvement in disease: Immunodeficiency with hyper-IgM 2 (HIGM2) [MIM:605258]: A rare immunodeficiency syndrome characterized by normal or elevated serum IgM levels with absence of IgG, IgA, and IgE. It results in a profound susceptibility to bacterial infections.Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.2

Sequence similarities: Belongs to the cytidine and deoxycytidylate deaminase family.