Insulin and dexamethasone regulation of a rat hepatoma messenger ribonucleic acid: insulin has a transcriptional and a posttranscriptional effect.
Experiments were conducted to investigate the actions of glucocorticoids and insulin on the induction of a specific mRNA (p33-mRNA) expressed in rat H4 hepatoma cells. Previous studies have found a 10-fold increase in this mRNA following 60 min of insulin addition. In the present study, dexamethasone (Dex) induced the cellular concentration of p33-mRNA 10- to 15-fold. This effect was time and dose dependent. The effect of Dex could be accounted for by a 10- to 15-fold increase in p33-mRNA transcription. However, insulin administration resulted in only a 3-fold increase in the transcription of p33-mRNA. The insulin induction of transcription was time and dose dependent and was blocked by the addition of alpha-amanitin. There was no increase in the transcription of a control gene, beta-tubulin, by either insulin or Dex. Neither insulin nor Dex altered the stability of p33-mRNA. Since the cellular concentration of p33-mRNA was induced to a greater extent than was transcription, insulin must be regulating at least one other step in the sequence between RNA synthesis and RNA stability.
Messina
J L
JL
Department of Physiology, State University of New York Health Science Center, Syracuse 13210.
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects*
D007328:Insulin; D012333:RNA, Messenger; D003907:Dexamethasone