title: Expression of the human PDGF-B gene is regulated by both positively and negatively acting cell type-specific regulatory elements located in the first intron.
abstract: Potential cis-acting regulatory elements of the human platelet derived growth factor-B (PDGF-B) gene were identified by DNase I hypersensitive site mapping. The transcription unit was examined for the presence of hypersensitive sites in chromatin DNA isolated from human term placental cytotrophoblasts, human placental fibroblasts, the JEG-3 choriocarcinoma cell line and the U2-OS osteosarcoma cell line. A number of cell type-specific hypersensitive sites were identified, all within the 1st intron. Transient transfection of JEG-3 cells with CAT constructs containing regions of the c-sis 1st intron linked to the basal c-sis promoter identified a cell type-specific positive regulatory activity within the intron, composed of at least two distinct elements. One element appeared to be specific for JEG-3 cells, while the other was also active in U2-OS cells. The overall positive regulatory activity of the 1st intron region was specific for JEG-3 cells, but did not function as a classically defined enhancer, as it was orientation-dependent (unless stably integrated into chromatin DNA). In addition, the activator appears to require interaction with the c-sis promoter, as little or no activation was seen when either the SV40 or human beta-globin promoters were substituted for the c-sis promoter. The 1st intron also contained a negative regulatory element, which was specific for U2-OS cells and silenced an abnormally high basal c-sis promoter activity in these cells. The complexity of the transcriptional control of the PDGF-B gene is discussed.
authors.affiliation: Laboratory for Molecular Development and Tumour Biology, Karolinska Institute, Stockholm, Sweden.
authors.forename: G C
authors.initials: GC
authors.lastname: Franklin
authors.forename: M
authors.initials: M
authors.lastname: Donovan
authors.forename: G I
authors.initials: GI
authors.lastname: Adam
authors.forename: L
authors.initials: L
authors.lastname: Holmgren
authors.forename: S
authors.initials: S
authors.lastname: Pfeifer-Ohlsson
authors.forename: R
authors.initials: R
authors.lastname: Ohlsson
mesh_terms: D001483:Base Sequence; D015152:Blotting, Northern; D004252:DNA Mutational Analysis; D003850:Deoxyribonuclease I / Q000494:pharmacology; D005786:Gene Expression Regulation; D005796:Genes; D006801:Humans; D066298:In Vitro Techniques; D007438:Introns; D008969:Molecular Sequence Data; D010920:Placenta / Q000502:physiology; D010982:Platelet-Derived Growth Factor / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020574:Proto-Oncogene Proteins c-sis; D012045:Regulatory Sequences, Nucleic Acid
chemical_list: D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D003850:Deoxyribonuclease I