AIDing the immune system-DIAbolic in cancer.

Activation induced deaminase (AID) has evolved with the immune system to enhance the ability of antibodies to bind and eliminate pathogens. It is a member of the AID/APOBEC family of proteins, which deaminate cytosine (or 5-methyl cytosine) in DNA leading to uracil (thymidine). These base modifications can lead to repair, DNA demethylation, mutagenesis, recombination, or viral/foreign DNA elimination. Because of their physiological function, their ubiquitous expression, and hormonal regulation (e.g. estrogen), these proteins play an important role in oncogenesis, with AID being directly implicated in B cell lymphomas. The targeting preference of each DNA deaminase provides a means to identify their mutation foot-print in tumours, and have implicated them in mutating the genome, including the loci of tumour suppressors, of various cancers (e.g. breast). In this special issue devoted to understanding AID function and regulation, leading members of the field discuss all aspects from AID transcriptional regulation, mRNA turnover, protein expression, modification, and transport, to complex formation, targeting and enzymatic turnover. AID's function will be discussed in context of DNA repair and how changes of key components of each pathway have an influence on the overall efficacy of targeted DNA deamination.