title: Class I and IIa histone deacetylases have opposite effects on sclerostin gene regulation.
abstract: Adult bone mass is controlled by the bone formation repressor sclerostin (SOST). Previously, we have shown that intermittent parathyroid hormone (PTH) bone anabolic therapy involves SOST expression reduction by inhibiting myocyte enhancer factor 2 (MEF2), which activates a distant bone enhancer. Here, we extended our SOST gene regulation studies by analyzing a role of class I and IIa histone deacetylases (HDACs), which are known regulators of MEF2s. Expression analysis using quantitative PCR (qPCR) showed high expression of HDACs 1 and 2, lower amounts of HDACs 3, 5, and 7, low amounts of HDAC4, and no expression of HDACs 8 and 9 in constitutively SOST-expressing UMR106 osteocytic cells. PTH-induced Sost suppression was associated with specific rapid nuclear accumulation of HDAC5 and co-localization with MEF2s in nuclear speckles requiring serine residues 259 and 498, whose phosphorylations control nucleocytoplasmic shuttling. Increasing nuclear levels of HDAC5 in UMR106 by blocking nuclear export with leptomycin B (LepB) or overexpression in transient transfection assays inhibited endogenous Sost transcription and reporter gene expression, respectively. This repressor effect of HDAC5 did not require catalytic activity using specific HDAC inhibitors. In contrast, inhibition of class I HDAC activities and expression using RNA interference suppressed constitutive Sost expression in UMR106 cells. An unbiased comprehensive search for involved HDAC targets using an acetylome analysis revealed several non-histone proteins as candidates. These findings suggest that PTH-mediated Sost repression involves nuclear accumulation of HDAC inhibiting the MEF2-dependent Sost bone enhancer, and class I HDACs are required for constitutive Sost expression in osteocytes.
authors.affiliation: From the Musculoskeletal Disease Area and.
authors.forename: Stefan
authors.initials: S
authors.lastname: Baertschi
authors.affiliation: Developmental and Molecular Pathways, Novartis Institutes for BioMedical Research, 4056 Basel, Switzerland.
authors.forename: Nina
authors.initials: N
authors.lastname: Baur
authors.affiliation: From the Musculoskeletal Disease Area and.
authors.forename: Valerie
authors.initials: V
authors.lastname: Lueders-Lefevre
authors.affiliation: Developmental and Molecular Pathways, Novartis Institutes for BioMedical Research, 4056 Basel, Switzerland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Voshol
authors.affiliation: From the Musculoskeletal Disease Area and hansjoerg.keller@novartis.com.
authors.forename: Hansjoerg
authors.initials: H
authors.lastname: Keller
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006655:Histone Deacetylases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D064326:MEF2 Transcription Factors / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009154:Mutation; D010011:Osteocytes / Q000187:drug effects / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D019485:Bone Morphogenetic Proteins; D005231:Fatty Acids, Unsaturated; D005819:Genetic Markers; D056572:Histone Deacetylase Inhibitors; D064326:MEF2 Transcription Factors; D010281:Parathyroid Hormone; C486031:Sost protein, rat; D049452:Green Fluorescent Proteins; C498619:Hdac5 protein, rat; D006655:Histone Deacetylases; C038753:leptomycin B
keywords: Gene Regulation; Histone Deacetylase (HDAC); Parathyroid Hormone; Sclerostin; Transcription Corepressor; Transcriptional Coactivator