title: Global relevance of Aire binding to hypomethylated lysine-4 of histone-3.
abstract: Aire promotes the ectopic expression of a repertoire of peripheral-tissue antigens (PTAs) in thymic medullary epithelial cells (MECs) to mediate deletional tolerance and thereby prevent autoimmunity. Binding of hypomethylated histone 3 (H3)-tails by Aire's plant homeodomain (PHD) finger is essential for Aire function in cultured cell models, prompting speculation that Aire-PHD:H3-tail interactions underlie targeting of Aire to weakly transcribed loci. To evaluate the role of Aire's PHD finger in MECs on a global scale in vivo, we complemented Aire-deficient mice with a mutant of Aire that inhibits its binding to hypomethylated H3K4 residues. Although the range of Aire-targeted genes was largely unaffected in these mice, the D299A mutation caused a global dampening of Aire's transcriptional impact, resulting in an autoimmune disease similar in profile to that of their Aire-deficient counterparts. To test whether a low H3K4 methylation state is sufficient for Aire targeting, we overexpressed an H3K4-specific demethylase in an Aire-dependent cultured cell system, and determined its capacity to extend Aire's transcriptional footprint. The range and magnitude of Aire-regulated genes was largely unaffected, the only genes additionally induced by Aire in this context being those already accessed for repression. In short, Aire's H3-binding module is necessary for Aire-mediated regulation of gene expression and central tolerance induction, but this influence is unlikely to reflect a targeting mechanism solely based on the recognition of hypomethylated H3K4 residues.
authors.affiliation: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Koh
authors.forename: Robert E
authors.initials: RE
authors.lastname: Kingston
authors.forename: Christophe
authors.initials: C
authors.lastname: Benoist
authors.forename: Diane
authors.initials: D
authors.lastname: Mathis
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism*; D007108:Immune Tolerance / Q000276:immunology; D008239:Lysine / Q000378:metabolism*; D008745:Methylation; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D010090:Oxidoreductases, O-Demethylating / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013950:Thymus Gland / Q000166:cytology; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D000096927:AIRE Protein
chemical_list: D006657:Histones; D008239:Lysine; D010090:Oxidoreductases, O-Demethylating; D012333:RNA, Messenger; D014157:Transcription Factors; D000096927:AIRE Protein