GSBS Student Publications

Title

Contributions of distal and proximal promoter elements to glucocorticoid regulation of osteocalcin gene transcription

GSBS Program

Biochemistry & Molecular Pharmacology

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Cell Biology

Date

6-1-1995

Document Type

Article

Medical Subject Headings

Animals; Base Sequence; Calcitriol; Consensus Sequence; DNA, Recombinant; Dexamethasone; Gene Expression Regulation, Neoplastic; Genes; Glucocorticoids; Molecular Sequence Data; Neoplasm Proteins; Osteoblasts; Osteocalcin; Osteosarcoma; *Promoter Regions (Genetics); Rats; Regulatory Sequences, Nucleic Acid; Sequence Deletion; Transcription, Genetic; Transfection; Tumor Cells, Cultured

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Previous studies identified several glucocorticoid response elements (GREs) in the 5'-promoter region of the rat osteocalcin (OC) gene by purified receptor binding. The present study addresses functionality of the GRE sequences in the proximal promoter at nucleotide (nt) -16 to -1 downstream of the TATA element together with the GRE half-element in the OC box at nt -86 to -81. This was done by assaying glucocorticoid responsiveness [at 10(-6) M dexamethasone (DEX)], and in combination with 10(-8) M 1,25-dihydroxyvitamin D3, of a series of deleted and mutated OC promoter reporter constructs (OCCAT) in osteoblast-like cells, the ROS 17/2.8 rat osteosarcoma line. Promoter deletion analysis revealed an additional GRE in the distal promoter at nt -697 to -683 that functions to suppress OC transcription. In the absence of this upstream negative GRE (nGRE), the -531 OCCAT construct exhibited enhanced promoter activity in response to DEX (1.8-fold DEX/Control), but further deletion (-348 and -108 OCCAT constructs) restored DEX suppression to OC promoter activity (0.6- and 0.8-fold DEX/Control, respectively). Mutations introduced in both the proximal GRE (nt -16 to -1) and the half-GRE in the OC box, or in the proximal GRE alone, nearly abrogated DEX responsiveness of OC promoter activity. Both distal and proximal GREs specifically bound glucocorticoid receptor present in ROS 17/2.8 nuclear extracts as shown by competition with wild type and mutated oligonucleotides and antibody inhibition of binding. Furthermore, both GREs, independently, conferred DEX-responsive transcriptional repression to the heterologous thymidine kinase basal promoter. We also report that glucocorticoid suppression of 1,25-dihydroxyvitamin D3-stimulated transcription occurs independently of distal or proximal GREs. Taken together, these results demonstrate that in vivo responsiveness of OC to DEX involves the integrative activities of several functional promoter elements.

Rights and Permissions

Citation: Mol Endocrinol. 1995 Jun;9(6):679-90.

Related Resources

Link to article in PubMed

Journal Title

Molecular endocrinology (Baltimore, Md.)

PubMed ID

8592514