Okadaic acid-dependent induction of the urokinase-type plasminogen activator gene associated with stabilization and autoregulation of c-Jun.
We have previously shown that the tumor promoter okadaic acid (OA), an inhibitor of protein phosphatases 1 and 2A, transcriptionally induces the urokinase-type plasminogen activator (uPA) gene in LLC-PK1 cells. This induction occurs independently of the protein kinase C- and cAMP-dependent signaling pathways. Here we show that a sequence located 2.0 kilobases upstream of the uPA gene, which resembles an AP-1-recognition sequence, mediates the action of OA. DNA-protein interaction studies, together with mRNA and protein analyses, indicate that c-Jun, but not c-Fos, is involved in OA-dependent uPA gene induction. The appearance of high levels of uPA mRNA and DNA binding activity of c-Jun to the AP-1-like site correspond to the appearance of c-Jun accumulation, suggesting that c-Jun accumulation is a critical event in OA-dependent uPA gene induction. c-Jun protein levels increase significantly between 100 and 160 min following OA treatment, whereas c-Jun translation increases only slightly in this time frame, suggesting that post-translation mechanisms are also involved in c-Jun accumulation. Pulse-chase analyses shows that OA specifically stabilizes c-Jun. We discuss our results with respect to the possibility that protein phosphatase 2A maintains c-Jun in its down-regulated state in LLC-PK1 cells.
Lee
J S
JS
Friedrich Miescher Institut, Basel, Switzerland.
Favre
B
B
Hemmings
B A
BA
Kiefer
B
B
Nagamine
Y
Y
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015139:Blotting, Southern; D015153:Blotting, Western; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000378:metabolism; D003078:Colchicine / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D004790:Enzyme Induction; D004988:Ethers, Cyclic / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005809:Genes, Regulator; D006706:Homeostasis; D007700:Kinetics; D008387:Marine Toxins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism; D019319:Okadaic Acid; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D010080:Oxazoles / Q000494:pharmacology; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000378:metabolism*; D013997:Time Factors; D015533:Transcriptional Activation; D014162:Transfection; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis* / Q000235:genetics
D004268:DNA-Binding Proteins; D004988:Ethers, Cyclic; D008387:Marine Toxins; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D010080:Oxazoles; D016755:Proto-Oncogene Proteins c-jun; D019319:Okadaic Acid; D015124:8-Bromo Cyclic Adenosine Monophosphate; C059041:calyculin A; D003513:Cycloheximide; D015500:Chloramphenicol O-Acetyltransferase; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases; D014568:Urokinase-Type Plasminogen Activator; D003078:Colchicine