title: The first intron of the human osteopontin gene contains a C/EBP-beta-responsive enhancer.
abstract: The osteopontin (OPN) protein is found expressed at high level in several processes including fibrotic evolution of organ injuries, tumorigenesis, and immune response. The molecular mechanisms that underly overexpression, especially at the transcriptional level, have been only partially clarified. Therefore, this study was undertaken in search for additional DNA elements in the regulatory regions of the OPN gene and cognate transcription factors. Our results on the region upstream of the transcription start site confirmed that essential elements are located within the first 100 bp. Analysis of the sequence that includes the first untranslated exon and first intron revealed that it could enhance the promoter activity. Experiments of transfection of constructs containing different fragments of this sequence showed that most of the enhancer activity was confined in the terminal 30-bp tract of the first intron, although it was not functioning in a myofibroblast cell line. DNA/protein binding assays and cotransfection experiments showed that the C/EBP-beta transcription factor was able to bind a recognition sequence in this 30-bp segment. We found a bi-allelic sequence polymorphism at +245 in the first intron, which did not show a significant functional effect, but is a useful tool for future association studies.
authors.affiliation: Laboratory of Molecular Genetics, G. Gaslini Institute, Largo G. Gaslini 5, 16148 Genova, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Giacopelli
authors.forename: Nadia
authors.initials: N
authors.lastname: Rosatto
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Divizia
authors.forename: Roberto
authors.initials: R
authors.lastname: Cusano
authors.forename: Gianluca
authors.initials: G
authors.lastname: Caridi
authors.forename: Roberto
authors.initials: R
authors.lastname: Ravazzolo
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics*; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D007438:Introns / Q000235:genetics*; D008969:Molecular Sequence Data; D053495:Osteopontin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D020218:Response Elements; D012795:Sialoglycoproteins / Q000235:genetics* / Q000378:metabolism; D024363:Transcription Initiation Site
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D010750:Phosphoproteins; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin; D004247:DNA