Parathyroid hormone induces c-fos promoter activity in osteoblastic cells through phosphorylated cAMP response element (CRE)-binding protein binding to the major CRE.
Many parathyroid hormone (PTH)-mediated events in osteoblasts are thought to require immediate early gene expression. PTH induces the immediate early gene, c-fos, in this cell type through a cAMP-dependent pathway. The present work investigated the nuclear mechanisms involved in PTH regulation of c-fos in the osteoblastic cell line, UMR 106-01. By transiently transfecting c-fos promoter 5' deletion constructs into UMR cells, we demonstrated that PTH induction of the c-fos promoter requires the major cAMP response element (CRE). Point mutations created in the major CRE within the largest construct inhibited both PTH-stimulated and basal expression. This element, therefore, performs concerted basal and PTH-responsive cis-acting functions. Gel retardation and Western blotting techniques revealed that CRE-binding protein (CREB) constitutively binds the major CRE but becomes phosphorylated at its cAMP-dependent protein kinase consensus recognition site following PTH treatment. CREB was functionally implicated in c-fos regulation by coexpressing a dominant CREB repressor, KCREB (killer CREB), with the c-fos promoter constructs. KCREB suppressed both basal and PTH-mediated c-fos induction. We conclude that PTH activates c-fos in osteoblasts through cAMP-dependent protein kinase-phosphorylated CREB interaction with the major CRE in the promoter region of the c-fos gene.
Pearman
A T
AT
Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Chou
W Y
WY
Bergman
K D
KD
Pulumati
M R
MR
Partridge
N C
NC
D000818:Animals; D001483:Base Sequence; D001859:Bone Neoplasms; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D016762:Genes, fos; D007700:Kinetics; D051379:Mice; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010766:Phosphorylation; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D011485:Protein Binding; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D017384:Sequence Deletion; D014162:Transfection
D017362:Cyclic AMP Response Element-Binding Protein; D015345:Oligonucleotide Probes; D010281:Parathyroid Hormone; D016760:Proto-Oncogene Proteins c-fos; D011993:Recombinant Fusion Proteins; D015500:Chloramphenicol O-Acetyltransferase