Negative and positive regulation of IGF-II mRNA expression in cultured rat cells by chicken serum.
We have investigated the possibility that some serum factors might negatively regulate the expression of the insulin-like growth factor-II (IGF-II) gene in 18-54, SF cells. Northern blot analyses indicated that there were three major transcripts (3.8 kb, 1.8 kb, and 1.2 kb) of the IGF-II gene in these cells. We found that incubation of 18-54, SF cells in medium containing very high concentrations (50-100%) of chicken serum greatly inhibited the steady-state level of all three IGF-II mRNA species. In addition, we also found that incubation of 18-54, SF cells in medium containing lower concentrations (10-50%) of chicken serum induced a 3.5 kb IGF-II mRNA. The inhibitory effect of high concentrations of chicken serum on IGF-II mRNA expression was not due to a cytotoxic effect of the serum, because these cells were maintained in 100% chicken serum for up to two weeks without loss of cell viability. The inhibitory effect of chicken serum on IGF-II mRNA was reversible after withdrawal of the serum. Nuclear run-on assays suggested that this negative regulation of IGF-II mRNA in 18-54, SF cells by chicken serum was not the result of transcriptional inhibition. Treatment of 18-54, SF cells that had been previously incubated in 100% chicken serum for 24 h with actinomycin D resulted in a partial restoration of the expression of the 3.8 kb and 1.2 kb IGF-II mRNA in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Han
Z
Z
Division of Biology and Medicine, Brown University, Providence, RI 02912.
Chatterjee
D
D
Bakker
A
A
Wyche
J H
JH
D000546:Amanitins / Q000494:pharmacology; D000818:Animals; D001769:Blood; D001798:Blood Proteins / Q000302:isolation & purification / Q000494:pharmacology; D015152:Blotting, Northern; D002460:Cell Line; D002645:Chickens / Q000097:blood; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D007700:Kinetics; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D014158:Transcription, Genetic
D000546:Amanitins; D001798:Blood Proteins; D003470:Culture Media; D012333:RNA, Messenger; D003609:Dactinomycin; D007335:Insulin-Like Growth Factor II; D003513:Cycloheximide