title: Paraspeckle protein p54nrb links Sox9-mediated transcription with RNA processing during chondrogenesis in mice.
abstract: The Sox9 transcription factor plays an essential role in promoting chondrogenesis and regulating expression of chondrocyte extracellular-matrix genes. To identify genes that interact with Sox9 in promoting chondrocyte differentiation, we screened a cDNA library generated from the murine chondrogenic ATDC5 cell line to identify activators of the collagen, type II, alpha 1 (Col2a1) promoter. Here we have shown that paraspeckle regulatory protein 54-kDa nuclear RNA-binding protein (p54nrb) is an essential link between Sox9-regulated transcription and maturation of Sox9-target gene mRNA. We found that p54nrb physically interacted with Sox9 and enhanced Sox9-dependent transcriptional activation of the Col2a1 promoter. In ATDC5 cells, p54nrb colocalized with Sox9 protein in nuclear paraspeckle bodies, and knockdown of p54(nrb) suppressed Sox9-dependent Col2a1 expression and promoter activity. We generated a p54nrb mutant construct lacking RNA recognition motifs, and overexpression of mutant p54nrb in ATDC5 cells markedly altered the appearance of paraspeckle bodies and inhibited the maturation of Col2a1 mRNA. The mutant p54nrb inhibited chondrocyte differentiation of mesenchymal cells and mouse metatarsal explants. Furthermore, transgenic mice expressing the mutant p54nrb in the chondrocyte lineage exhibited dwarfism associated with impairment of chondrogenesis. These data suggest that p54nrb plays an important role in the regulation of Sox9 function and the formation of paraspeckle bodies during chondrogenesis.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hata
authors.forename: Riko
authors.initials: R
authors.lastname: Nishimura
authors.forename: Shuji
authors.initials: S
authors.lastname: Muramatsu
authors.forename: Akio
authors.initials: A
authors.lastname: Matsuda
authors.forename: Takuma
authors.initials: T
authors.lastname: Matsubara
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Amano
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Ikeda
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Harley
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yoneda
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002454:Cell Differentiation; D020219:Chondrogenesis / Q000235:genetics*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D034521:Nuclear Matrix-Associated Proteins / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D055758:SOX9 Transcription Factor; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D004268:DNA-Binding Proteins
chemical_list: D006609:High Mobility Group Proteins; D034521:Nuclear Matrix-Associated Proteins; D012313:RNA; D016601:RNA-Binding Proteins; D055758:SOX9 Transcription Factor; D014157:Transcription Factors; C527932:SOX9 protein, human; C527933:Sox9 protein, mouse; C500331:Nono protein, mouse; D004268:DNA-Binding Proteins