Regulation of tyrosinase mRNA in mouse melanoma cells by alpha-melanocyte-stimulating hormone.
Cloudman S-91 mouse melanoma cells respond to alpha-melanocyte-stimulating hormone) by demonstrating a marked increase in tyrosinase activity (O-diphenol-O2 oxidoreductase, EC 1.14.18.1). This increase is the result of increased levels of tyrosinase mRNA with a subsequent increase in tyrosinase abundance. Our studies were carried out to determine the effect of melanocyte-stimulating hormone on tyrosinase gene transcription and to measure the kinetics of the hormone-induced increase in tyrosinase mRNA. When melanoma cells were exposed continuously to melanocyte-stimulating hormone for 6 d, a large but transient increase in both tyrosinase mRNA abundance and enzyme activity were observed. The maximum increase in tyrosinase mRNA occurred 60 h after melanocyte-stimulating hormone stimulation and was followed by a decline in message levels even though cells were continuously exposed to hormone. Results of nuclear run-off transcription assays showed that melanocyte-stimulating hormone caused a slow increase in the rate of transcription of the tyrosinase gene with a maximal 6-fold stimulation occurring at 48 h. In cells treated with the ribonucleic acid synthesis inhibitor, 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, tyrosinase mRNA levels decayed with a half-life of 4-5 h. This decay rate was unaffected by treatment of cells with melanocyte-stimulating hormone, indicating that the hormone does not act to stabilize tyrosinase ribonucleic acid. Inhibition of protein synthesis by treatment with cycloheximide had no effect on the melanocyte-stimulating hormone-induced increase in tyrosinase messenger ribonucleic acid levels suggesting that ongoing protein synthesis is not required for, at least, the initial stimulation of tyrosinase gene transcription by melanocyte-stimulating hormone.
Rungta
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Department of Biochemistry and Molecular Biology, University of Oklahoma, Health Science Center, Oklahoma City, USA.
Corn
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Fuller
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D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D000242:Cyclic AMP / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D008546:Melanoma, Experimental / Q000201:enzymology*; D051379:Mice; D014442:Monophenol Monooxygenase / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D014158:Transcription, Genetic / Q000187:drug effects
D012333:RNA, Messenger; D009074:Melanocyte-Stimulating Hormones; D003513:Cycloheximide; D000242:Cyclic AMP; D014442:Monophenol Monooxygenase; D015500:Chloramphenicol O-Acetyltransferase