Transcriptional activation of the human osteocalcin gene by basic fibroblast growth factor.
Basic fibroblast growth factor (bFGF) has been detected in bone cells and stimulates osteoblast proliferation; however, its role in the regulation of bone metabolism remains speculative. We demonstrated that the human osteocalcin promoter is activated by bFGF when transfected into rat osteoblastic (ROS 17/2.8) cells. This effect is concentration dependent, with a twofold induction at 10 ng/ml detected after 20 h. The bFGF response is independent of both the 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and retinoic acid activation of the osteocalcin promoter. To identify the promoter sequences through which bFGF exerts its effect, we tested a series of promoter deletion constructs for their response to bFGF. Deletion of the upstream region between -673 and -588 bp results in a significant loss of induction. Gel-shift analysis demonstrates that proteins present in ROS 17/2.8 nuclear extracts bind specifically to these sequences. This region alone was unable to confer the bFGF response on a minimal osteocalcin or an heterologous promoter. However, sequences between -678 and -476 bp, which also includes the vitamin D response element (VDRE), were able to confer bFGF inducibility on both a minimal osteocalcin and a heterologous promoter. These data suggest that induction of the human osteocalcin promoter by bFGF requires the interaction of more than one sequence element.
Schedlich
L J
LJ
Bone and Mineral Research Group, Garvan Institute of Medical Research, St. Vincent's Hospital, Darlinghurst, Sydney, Australia.
Flanagan
J L
JL
Crofts
L A
LA
Gillies
S A
SA
Goldberg
D
D
Morrison
N A
NA
Eisman
J A
JA
D000818:Animals; D001483:Base Sequence; D002117:Calcitriol / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics*; D012516:Osteosarcoma; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D017384:Sequence Deletion; D014158:Transcription, Genetic / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D016222:Fibroblast Growth Factor 2; D015675:Osteocalcin; D014212:Tretinoin; D002117:Calcitriol