Parathyroid hormone versus phorbol ester stimulation of activator protein-1 gene family members in rat osteosarcoma cells.
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.
Koe
R C
RC
Department of Pharmacological and Physiological Science, St. Louis University Health Sciences Center, 1402 South Grand Boulevard, St. Louis, Missouri 63104, USA.
Clohisy
J C
JC
Tyson
D R
DR
Pulumati
M R
MR
Cook
T F
TF
Partridge
N C
NC
D000818:Animals; D015152:Blotting, Northern; D001859:Bone Neoplasms / Q000235:genetics* / Q000473:pathology; D002273:Carcinogens / Q000633:toxicity*; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D017364:Collagenases / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D017930:Genes, Reporter / Q000187:drug effects / Q000235:genetics; D016762:Genes, fos / Q000187:drug effects / Q000235:genetics; D016758:Genes, jun / Q000187:drug effects / Q000235:genetics; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology; D012516:Osteosarcoma / Q000235:genetics* / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D019379:Teriparatide / Q000633:toxicity*; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity*; D018808:Transcription Factor AP-1 / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D000099169:Fos-Related Antigen 1
D002273:Carcinogens; D015500:Chloramphenicol O-Acetyltransferase; D017364:Collagenases; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D019379:Teriparatide; D013755:Tetradecanoylphorbol Acetate; D018808:Transcription Factor AP-1; D000099169:Fos-Related Antigen 1