Human Activation-Induced Cytidine Deaminase (AICDA) Protein

Background

Activation-induced cytidine deaminase (AICDA) is an enzyme crucial for the adaptive immune system, specifically in antibody diversification processes. AICDA is primarily expressed in activated B cells within germinal centers and is a key mediator of somatic hypermutation (SHM) and class switch recombination (CSR) in immunoglobulin genes. Through its enzymatic activity, AICDA deaminates cytidine residues in single-stranded DNA, converting them into uracil during transcription, which introduces mutations or facilitates recombination. This targeted mutagenesis is essential for generating high-affinity antibodies and diversifying antibody classes, enabling the immune system to respond effectively to a wide range of antigens. Dysregulation or mutations in AICDA have been linked to immunodeficiency disorders, such as hyper-IgM syndrome, and its aberrant activity is implicated in genomic instability, contributing to oncogenic mutations in lymphomas. AICDA expression is tightly regulated by transcription factors, including E2F and NF-κB, and is further controlled by post-translational modifications such as phosphorylation. Understanding the precise mechanisms of AICDA function and regulation remains critical, as its activity represents both a cornerstone of adaptive immunity and a potential contributor to mutagenesis in malignancies. Researchers continue to explore AICDA as a target for therapeutic intervention in autoimmune diseases and cancer.