title: Hmgb1 can facilitate activation of the matrilin-1 gene promoter by Sox9 and L-Sox5/Sox6 in early steps of chondrogenesis.
abstract: The architectural high mobility group box 1 (Hmgb1) protein acts as both a nuclear and an extracellular regulator of various biological processes, including skeletogenesis. Here we report its contribution to the evolutionarily conserved, distinctive regulation of the matrilin-1 gene (Matn1) expression in amniotes. We previously demonstrated that uniquely assembled proximal promoter elements restrict Matn1 expression to specific growth plate cartilage zones by allowing varying doses of L-Sox5/Sox6 and Nfi proteins to fine-tune their Sox9-mediated transactivation. Here, we dissected the regulatory mechanisms underlying the activity of a conserved distal promoter element 1. We show that this element carries three Sox-binding sites, works as an enhancer in vivo, and allows promoter activation by the Sox5/6/9 chondrogenic trio. In early steps of chondrogenesis, declining Hmgb1 expression overlaps with the onset of Sox9 expression. Unlike repression in late steps, Hmgb1 overexpression in early chondrogenesis increases Matn1 promoter activation by the Sox trio, and forced Hmgb1 expression in COS-7 cells facilitates induction of Matn1 expression by the Sox trio. The conserved Matn1 control elements bind Hmgb1 and SOX9 with opposite efficiency in vitro. They show higher HMGB1 than SOX trio occupancy in established chondrogenic cell lines, and HMGB1 silencing greatly increases MATN1 and COL2A1 expression. Together, these data thus suggest a model whereby Hmgb1 helps recruit the Sox trio to the Matn1 promoter and thereby facilitates activation of the gene in early chondrogenesis. We anticipate that Hmgb1 may similarly affect transcription of other cartilage-specific genes.
authors.affiliation: Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, H-6701 Szeged, Hungary. Electronic address: sztibor@brc.hu.
authors.forename: Tibor
authors.initials: T
authors.lastname: Szénási
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Kénesi
authors.forename: Andrea
authors.initials: A
authors.lastname: Nagy
authors.forename: Annamária
authors.initials: A
authors.lastname: Molnár
authors.forename: Bálint László
authors.initials: BL
authors.lastname: Bálint
authors.forename: Ágnes
authors.initials: Á
authors.lastname: Zvara
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Csabai
authors.forename: Ferenc
authors.initials: F
authors.lastname: Deák
authors.forename: Beáta
authors.initials: B
authors.lastname: Boros Oláh
authors.forename: Lajos
authors.initials: L
authors.lastname: Mátés
authors.forename: László
authors.initials: L
authors.lastname: Nagy
authors.forename: László G
authors.initials: LG
authors.lastname: Puskás
authors.forename: Ibolya
authors.initials: I
authors.lastname: Kiss
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D019556:COS Cells; D002478:Cells, Cultured; D002642:Chick Embryo; D002522:Chlorocebus aethiops; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D020219:Chondrogenesis / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D005455:Fluorescent Antibody Technique; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D064235:Matrilin Proteins / Q000235:genetics* / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020218:Response Elements / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D055755:SOXD Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D024243:HMGB1 Protein; D064235:Matrilin Proteins; D012333:RNA, Messenger; D055758:SOX9 Transcription Factor; D055755:SOXD Transcription Factors
keywords: CEC; CEF; Cartilage-specific regulation; ChIP; Chromatin immunoprecipitation; Dpe1 and Dpe2; ECM; EMSA; GP; GST; Growth plate; HDM; HMG; HMG box; Hmgb; Ine; LDM; LM-PCR; Matrilin; Nfi; Pe1; RCS; SI and SII; Silencing; Transgenic mice; chicken embryo chondrocyte; chicken embryo fibroblast; chromatin immunoprecipitation; distal promoter upstream elements 1 and 2; electrophoretic mobility shift assay; extracellular matrix; glutathione S-transferase; growth plate; high density mesenchyme; high-mobility-group; initiator element; ligation-mediated PCR; low density mesenchyme; nuclear factor I; promoter element 1; rat chondrosarcoma; silencer elements I and II