title: JunB is involved in the inhibition of myogenic differentiation by bone morphogenetic protein-2.
abstract: Bone morphogenetic proteins (BMPs) constitute a family of multifunctional growth and differentiation factors structurally related to transforming growth factor-beta. BMPs were first identified by their osteoinductive effects, inducing ectopic bone formation when implanted in skeletal muscle, and have an important role as regulators of skeletal development in vivo. In vitro, BMP-2 is able to transdifferentiate myogenic C2C12 cells into the osteoblastic phenotype. In this report, we show that the osteoinductive effects of BMP-2 in C2C12 cells are mediated by bone morphogenetic protein receptor type-IA in combination with both activin receptor type II and bone morphogenetic protein receptor type II. We also analyzed the expression levels of nuclear protooncogenes to understand early transcriptional events induced by BMP-2. We show that junB is an immediate early gene induced by BMP-2 and transforming growth factor-beta. BMP-2 induces transcriptional activation of JunB expression as early as 30 min after ligand addition, reaching maximal levels after 90 min. Increase of JunB mRNA correlates with a higher AP-1 binding activity. Furthermore, ectopic overexpression of JunB is sufficient to inhibit expression of myoblast differentiation markers in C2C12 cells. These data, taken together, show the involvement of JunB in the early steps of inhibition of myogenic differentiation induced by transforming growth factor-beta family members.
authors.affiliation: Unitat de Bioquímica, Campus de Bellvitge, Universitat de Barcelona, Feixa Llarga s/n, 08907 Hospitalet de Llobregat, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Chalaux
authors.forename: T
authors.initials: T
authors.lastname: López-Rovira
authors.forename: J L
authors.initials: JL
authors.lastname: Rosa
authors.forename: R
authors.initials: R
authors.lastname: Bartrons
authors.forename: F
authors.initials: F
authors.lastname: Ventura
mesh_terms: D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology; D017781:Genes, Immediate-Early; D018482:Muscle, Skeletal / Q000166:cytology*; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D015500:Chloramphenicol O-Acetyltransferase