Autoimmune regulator (APECED) is a transcriptional regulator that binds to DNA as a dimer or as a tetramer, but not as a monomer. APECED binds to G-doublets in an A/T-rich environment; the preferred motif is a tandem repeat of 5'-. ATTGGTTA-3' combined with a 5'-TTATTA-3' bo, Xenopus/Amphibian,. APECED binds to chromatin and interacts selectively with histone H3 that is not methylated at 'Lys-4', not phosphorylated at 'Thr-3' and not methylated at 'Arg-2'. APECED functions as a sensor of histone H3 modifications that are important for the epigenetic regulation of gene e, Xenopus/Amphibian,pression. APECED functions as a transcriptional activator and promotes the e, Xenopus/Amphibian,pression of otherwise tissue-specific self-antigens in the thymus, which is important for self tolerance and the avoidance of autoimmune reactions. Defects in APECED are a cause of autoimmune poly-endocrinopathy candidiasis ectodermal dystrophy (APECED), also known as autoimmune polyglandular syndrome type I (APS-1). APECED is an autosomal recessive disease characterized by: (1) autoimmune polyendocrinopathies; (2) chronic mucocutaneous candidiasis; and (3) ectodermal dystrophies. In addition, a high proportion of patients develop squamous cell carcinoma of the oral mucosa. The disease is reported worldwide but is e, Xenopus/Amphibian,ceptionally prevalent among the Finnish population (incidence 1:25000) and the Iranian jews (incidence 1:9000).