title: SHARP1/DEC2 inhibits adipogenic differentiation by regulating the activity of C/EBP.
abstract: SHARP1, a basic helix-loop-helix transcription factor, is expressed in many cell types; however, the mechanisms by which it regulates cellular differentiation remain largely unknown. Here, we show that SHARP1 negatively regulates adipogenesis. Although expression of the early marker CCAAT/enhancer binding protein beta (C/EBPbeta) is not altered, its crucial downstream targets C/EBPalpha and peroxisome proliferator-activated receptor gamma (PPARgamma) are downregulated by SHARP1. Protein interaction studies confirm that SHARP1 interacts with and inhibits the transcriptional activity of both C/EBPbeta and C/EBPalpha, and enhances the association of C/EBPbeta with histone deacetylase 1 (HDAC1). Consistently, in SHARP1-expressing cells, HDAC1 and the histone methyltransferase G9a are retained at the C/EBP regulatory sites on the C/EBPalpha and PPARgamma2 promoters during differentiation, resulting in inhibition of their expression. Interestingly, treatment with troglitazone results in displacement of HDAC1 and G9a, and rescues the differentiation defect of SHARP1-overexpressing cells. Our data indicate that SHARP1 inhibits adipogenesis through the regulation of C/EBP activity, which is essential for PPARgamma-ligand-dependent displacement of co-repressors from adipogenic promoters.
authors.affiliation: Department of Developmental and Regenerative Biology, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Neriman Tuba
authors.initials: NT
authors.lastname: Gulbagci
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Belinda
authors.initials: B
authors.lastname: Ling
authors.forename: Suma
authors.initials: S
authors.lastname: Gopinadhan
authors.forename: Martin
authors.initials: M
authors.lastname: Walsh
authors.forename: Moritz
authors.initials: M
authors.lastname: Rossner
authors.forename: Klaus-Armin
authors.initials: KA
authors.lastname: Nave
authors.forename: Reshma
authors.initials: R
authors.lastname: Taneja
mesh_terms: D050156:Adipogenesis; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D002478:Cells, Cultured; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D051379:Mice; D018345:Mice, Knockout; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011496:Protein Methyltransferases / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: C470968:Bhlhb3 protein, mouse; D022763:CCAAT-Enhancer-Binding Protein-alpha; D022782:CCAAT-Enhancer-Binding Protein-beta; D014157:Transcription Factors; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D006655:Histone Deacetylases