9192514

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1

We have previously shown that in the rat osteoblastic osteosarcoma cell line-UMR 106-01-PTH induces maximal collagenase mRNA levels at 4 hours. Since this response to PTH requires de novo protein synthesis, it may be mediated by the combined temporal expression of members of the activator protein-1 (AP-1) gene family. We have demonstrated that maximal mRNA levels of two of the members of this family, c-fos and c-jun, occur 30 min after stimulation by PTH. Phorbol myristate acetate (PMA) elicits a similar increase in c-fos and c-jun mRNAs, but is unable to stimulate transcription of collagenase in these cells. To investigate further the involvement of the AP-1 gene family, we examined PTH and PMA stimulation of jun-B, jun-D, fos B, and fra-1 mRNAs in UMR 106-01 cells. The mRNA for jun-D was abundant under control conditions and showed no variation in response to PTH (10(-8) M). The fos B transcripts were not detected under control conditions, whereas jun-B and fra-1 mRNAs were present at low basal levels. PTH caused an increase in fos B mRNA that reached a maximal 4- to 5-fold plateau between 45 and 60 min. An increase in jun-B mRNA in response to PTH was detectable at 30 min, but reached a maximal 6- to 7-fold increase at 2 hours. After PTH stimulation, the fra-1 transcript showed a 10- to 11-fold peak at 4 hours. PMA (2.6 x 10(-7) M) stimulated fos B mRNA to maximal abundance at 1 hour, similar to PTH. In contrast, PMA caused a maximal increase in jun-B mRNA at 30 min and fra-1 mRNA at 2 hours, which was earlier than the response to PTH. To determine whether an increase in jun-B at the same time as c-fos and c-jun would inhibit collagenase gene transcription, we cotransfected an expression vector for jun-B with a rat collagenase promoter-reporter gene construct. This resulted in a decrease in PTH-stimulation of promoter activity. Thus, it appears that the differential temporal stimulation of the AP-1 genes by PTH and PMA, particularly an increase in jun-B at the same time as c-fos and c-jun, explains the difference seen in their ability to induce transcription of collagenase.

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MEDLINE

0171-967X

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52-8

pubmed-meshheading:9192514-Animals, pubmed-meshheading:9192514-Blotting, Northern, pubmed-meshheading:9192514-Bone Neoplasms, pubmed-meshheading:9192514-Carcinogens, pubmed-meshheading:9192514-Chloramphenicol O-Acetyltransferase, pubmed-meshheading:9192514-Collagenases, pubmed-meshheading:9192514-Gene Expression Regulation, Neoplastic, pubmed-meshheading:9192514-Genes, Reporter, pubmed-meshheading:9192514-Genes, fos, pubmed-meshheading:9192514-Genes, jun, pubmed-meshheading:9192514-Osteoblasts, pubmed-meshheading:9192514-Osteosarcoma, pubmed-meshheading:9192514-Promoter Regions, Genetic, pubmed-meshheading:9192514-Proto-Oncogene Proteins c-fos, pubmed-meshheading:9192514-RNA, Messenger, pubmed-meshheading:9192514-Rats, pubmed-meshheading:9192514-Teriparatide, pubmed-meshheading:9192514-Tetradecanoylphorbol Acetate, pubmed-meshheading:9192514-Transcription, Genetic, pubmed-meshheading:9192514-Transcription Factor AP-1, pubmed-meshheading:9192514-Transfection, pubmed-meshheading:9192514-Tumor Cells, Cultured

Parathyroid hormone versus phorbol ester stimulation of activator protein-1 gene family members in rat osteosarcoma cells.

Journal Article, Research Support, Non-U.S. Gov't