title: Recruitment of nuclear factor Y to the inverted CCAAT element (ICE) by c-Jun and E1A stimulates basal transcription of the bone sialoprotein gene in osteosarcoma cells.
abstract: Bone sialoprotein (BSP), a major protein in the extracellular matrix of bone, is expressed almost exclusively by bone cells and by cancer cells that have a propensity to metastasize to bone. Previous studies have shown that v-src stimulates basal transcription of bsp in osteosarcoma (ROS 17/2.8) cells by targeting the inverted CCAAT element (ICE) in the proximal promoter. To identify possible downstream effectors of Src we studied the effects of the proto-oncogene c-jun, which functions downstream of Src, on basal transcription of bsp using transient transfection assays. Increased expression of endogenous c-Jun induced by the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate and ectopic expression of c-Jun increased basal transcription of chimeric reporter constructs encompassing the proximal promoter by 1.5-3-fold in ROS 17/2.8 osteosarcoma cells, with more modest effects in a normal bone cell line, RBMC-D8. The effects of c-Jun were abrogated by mutations in the ICE box and by co-expression of dominant negative nuclear factor Y, subunit A (NF-YA). The increase in bsp transcription did not require phosphorylation of c-Jun and was not altered by trichostatin treatment or by ectopic expression of p300/CREB-binding protein (CBP) or mutated forms lacking histone acetyltransferase (HAT) activity. Similarly, ectopic expression of p300/CBP-associated factor (P/CAF), which transduces p300/CBP effects, or of HAT-defective P/CAF did not influence the c-jun effects. Surprisingly, E1A, which competes with P/CAF binding to p300/CBP, also stimulated BSP transcription through NF-Y independently of c-jun, p300/CBP, and P/CAF. Collectively, these studies show that c-Jun and E1A regulate basal transcription of bsp in osteosarcoma cells by recruiting the NF-Y transcriptional complex to the ICE box in a mechanism that is independent of p300/CBP and P/CAF HAT activities.
authors.affiliation: Canadian Institutes of Health Research Group in Matrix Dynamics, Faculty of Dentistry, University of Toronto, ON. m.su@utoronto.ca
authors.forename: Ming
authors.initials: M
authors.lastname: Su
authors.forename: Anil K
authors.initials: AK
authors.lastname: Bansal
authors.forename: Roberto
authors.initials: R
authors.lastname: Mantovani
authors.forename: Jaro
authors.initials: J
authors.lastname: Sodek
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001854:Bone Marrow Cells / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism; D023081:CCAAT-Binding Factor / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D053938:DNA Fragmentation; D017931:DNA Primers / Q000737:chemistry; D050881:E1A-Associated p300 Protein / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D015972:Gene Expression Regulation, Neoplastic; D005799:Genes, Dominant; D017930:Genes, Reporter; D005822:Genetic Vectors; D051548:Histone Acetyltransferases / Q000378:metabolism; D006657:Histones / Q000737:chemistry / Q000378:metabolism; D006877:Hydroxamic Acids / Q000494:pharmacology; D058574:Integrin-Binding Sialoprotein; D008969:Molecular Sequence Data; D009154:Mutation; D012516:Osteosarcoma / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000235:genetics; D017154:Stromal Cells / Q000166:cytology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D050880:p300-CBP Transcription Factors / Q000378:metabolism
chemical_list: D023081:CCAAT-Binding Factor; D017931:DNA Primers; D006657:Histones; D006877:Hydroxamic Acids; D058574:Integrin-Binding Sialoprotein; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; D012795:Sialoglycoproteins; D014157:Transcription Factors; C402244:nuclear factor Y; C012589:trichostatin A; D050881:E1A-Associated p300 Protein; D051548:Histone Acetyltransferases; D050880:p300-CBP Transcription Factors; D013755:Tetradecanoylphorbol Acetate