Regulation of c-jun gene expression in endothelial cells by the protein kinase inhibitor staurosporine.
The proto-oncogene c-jun, a member of the family of immediate-early genes, is transcriptionally induced in different cell types by a variety of stimuli, including mitogens, tumor promoters, growth factors. We show here that the protein kinase inhibitor staurosporine, which inhibits both the serine-threonine and tyrosine specific protein kinases, also causes differential regulation of the c-jun gene in endothelial cells. Increasing concentrations of staurosporine modulated the steady-state levels of c-jun mRNA in bovine aortic endothelial (BAE) cells in a multiphasic manner. The half-life of c-jun mRNA did not change significantly under these conditions, suggesting that the modulations in the mRNA levels were caused primarily by differential transcriptional activity of the gene. The expression of c-jun gene is believed to be regulated by its own product, the JUN protein, which constitutes a major component of the inducible transcription factor AP-1. In order to test whether the differential regulation of c-jun gene was caused by the differential activation (or inactivation) of the AP-1 transcription factor, the DNA-binding activity of this transcription factor in staurosporine-treated cells was measured. Gelshift analysis with a synthetic oligonucleotide probe showed modest effects of staurosporine on the DNA-binding activity of the transcription factor AP-1. The changes observed in the DNA-binding activity of AP-1 did not parallel the changes observed in the steady-state levels of c-jun mRNA. Similarly, the expression of an AP-1 dependent reporter gene construct was regulated in a fashion entirely different from the c-jun gene during the same protein kinase inhibitory conditions. These results suggest the existence of an alternative pathway that regulates the c-jun gene expression in endothelial cells independent of both the protein kinase and AP-1 transcription factor activation steps.
Bandyopadhyay
R S
RS
Cancer Research Center, Boston University School of Medicine, MA 02118, USA.
Faller
D V
DV
D000818:Animals; D001013:Aorta, Thoracic; D002417:Cattle; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D004247:DNA / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D016758:Genes, jun; D047428:Protein Kinase Inhibitors; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects*; D019311:Staurosporine / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000502:physiology; D014162:Transfection
D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase; D019311:Staurosporine