Topic summary
Activation-induced cytidine deaminase
Activation-induced cytidine deaminase, also known as AICDA, AID and single-stranded DNA cytosine deaminase, is a 24 kDaenzyme which in humans is encoded by the AICDAgene. It creates mutations in DNA by deamination of cytosine base, which turns it into uracil (which is recognized as a thymine). In other words, it changes a C:G base pair into a U:G mismatch. AID is a member of the APOBEC family.
The cell's DNA replication machinery recognizes the U as a T, and hence C:G is converted to a T:A base pair. During germinal center development of B cells, error-prone DNA repair following AID action also generates other types of mutations, such as C:G to A:T. In B cells in the lymph nodes, AID causes mutations that produce antibody diversity, but that same mutation process can also lead to B-cell lymphoma.