title: Id3 is a direct transcriptional target of Pax7 in quiescent satellite cells.
abstract: Pax7 is a key regulator of skeletal muscle stem cells and is required along with Pax3 to generate skeletal muscle precursors. We have identified a collection of genes induced by either Pax3 or Pax7 in C2C12 muscle cells. Two notable Pax3/7 targets are the inhibitory helix-loop-helix (HLH) proteins inhibitor of DNA binding (Id) 2 and Id3, both of which are coordinately expressed with Pax7 in quiescent satellite cells and are induced in quiescent C2C12 myogenic cells after ectopic expression of either Pax3 or Pax7. Ectopic Pax7 activates expression of a luciferase reporter driven by the Id3 promoter, and maximal induction of this reporter requires a conserved Pax7 binding site located upstream of the Id3 gene. Chromatin immunoprecipitation indicated that Pax7 is bound upstream of the Id3 promoter in quiescent satellite cells. In addition, short hairpin RNA-mediated knockdown of Pax7 expression in cultured satellite cells coordinately decreased both Id2 and Id3 expression. Together, these findings indicate that Id3 is a direct transcriptional target for Pax7 in quiescent satellite cells, and they suggest that Pax7 acts to block premature differentiation of quiescent satellite cells by inducing the expression of Id2 and Id3, which in turn may act to block either the precocious induction of myogenic basic (b)HLH proteins, the activity of myogenic bHLH proteins, or both.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kumar
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Shadrach
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Wagers
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Lassar
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D051797:Inhibitor of Differentiation Protein 2 / Q000235:genetics / Q000378:metabolism; D051796:Inhibitor of Differentiation Proteins / Q000235:genetics / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C497452:Idb2 protein, mouse; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor; D051761:Paired Box Transcription Factors; C497322:Pax7 protein, mouse; D034741:RNA, Small Interfering; C067679:Idb3 protein, mouse; C068686:Pax3 protein, mouse; D008156:Luciferases