Regulation of c-jun expression during induction of monocytic differentiation by okadaic acid.
The present work has examined the effects of okadaic acid, an inhibitor of type 1 and 2A protein phosphatases, on the regulation of c-jun expression during monocytic differentiation of U-937 leukemia cells. The results demonstrate that okadaic acid treatment is associated with induction of a differentiated monocyte phenotype characterized by: (a) growth arrest; (b) increases in Mac-1 cell surface antigen expression; (c) down-regulation of c-myc transcripts; and (d) induction of tumor necrosis factor gene expression. This induction of monocytic differentiation was associated with transient increases in c-jun mRNA levels, which were maximal at 6 h. Similar effects were obtained for the c-fos gene. Run-on analysis demonstrated detectable levels of c-jun transcription in U-937 cells and that this rate is increased approximately 40-fold following okadaic acid exposure. c-jun mRNA levels were superinduced in cells treated with both okadaic acid and cycloheximide, whereas inhibition of protein synthesis had little, if any, effect on okadaic acid-induced c-jun transcription. The half-life of c-jun mRNA was similar (45-50 min) in both untreated and okadaic acid-induced cells. In contrast, treatment with both okadaic acid and cycloheximide was associated with stabilization (t 1/2 = 90 min) of c-jun transcripts. Taken together, these findings indicate that the induction of c-jun transcription by okadaic acid is controlled primarily by a transcriptional mechanism. Since previous studies have demonstrated that the c-jun gene is autoinduced by Jun/AP-1, we also studied transcription of c-jun promoter (positions -132/+170)-reporter gene constructs with and without a mutated AP-1 element.(ABSTRACT TRUNCATED AT 250 WORDS)
Kharbanda
S
S
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Datta
R
R
Rubin
E
E
Nakamura
T
T
Hass
R
R
Kufe
D
D
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology*; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D016758:Genes, jun / Q000187:drug effects*; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000473:pathology; D008297:Male; D009000:Monocytes / Q000187:drug effects* / Q000473:pathology; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000473:pathology; D019319:Okadaic Acid; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis* / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects
D004988:Ethers, Cyclic; D007546:Isoquinolines; D009363:Neoplasm Proteins; D010879:Piperazines; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D003609:Dactinomycin; D019319:Okadaic Acid; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D003513:Cycloheximide; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate