title: NF1/X represses PDGF A-chain transcription by interacting with Sp1 and antagonizing Sp1 occupancy of the promoter.
abstract: The regulatory mechanisms mediating basal and inducible platelet-derived growth factor (PDGF)-A expression have been the focus of intense recent investigation, but repression of PDGF-A expression is largely unexplored. Here we isolated a nuclear factor that interacts with the proximal region of the PDGF-A promoter using bulk binding assays and chromatography techniques. Peptide mass fingerprint and supershift analysis revealed this DNA-binding protein to be NF1/X. NF1/X repressed PDGF-A promoter-dependent transcription and endogenous mRNA expression, which was reversible by oligonucleotide decoys bearing an NF1/X-binding site. Mutation in the DNA-binding domain of NF1/X abolished its repression of PDGF-A promoter. NF1/X antagonized the activity of a known activator of the PDGF-A chain, Sp1, by inhibiting its occupancy of the proximal PDGF-A promoter. NF1/X physically and specifically interacts with Sp1 via its subtype-specific domain and blocks Sp1 induction of the promoter. NF1/X residues 311-416 mediated NF1/X suppression of basal PDGF-A transcription, whereas residues 243-416 were required for NF1/X repression of Sp1-inducible promoter activity. These findings demonstrate that repression of PDGF-A gene transcription is governed by interplay between NF1/X and Sp1.
authors.affiliation: Centre for Thrombosis and Vascular Research, Department of Pathology, The University of New South Wales, Sydney, Australia.
authors.forename: Louise A
authors.initials: LA
authors.lastname: Rafty
authors.forename: Fernando S
authors.initials: FS
authors.lastname: Santiago
authors.forename: Levon M
authors.initials: LM
authors.lastname: Khachigian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D004268:DNA-Binding Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D051839:NFI Transcription Factors; D009687:Nuclear Proteins / Q000235:genetics; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D016329:Sp1 Transcription Factor / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D010982:Platelet-Derived Growth Factor; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; C075278:platelet-derived growth factor A; C080333:transcription factor nuclear factor 1