Post-transcriptional regulation of collagen alpha 1(I) mRNA in hepatic stellate cells.

Posttranscriptional events may play an important role in regulating collagen alpha 1(I) mRNA in hepatic stellate cells. Quiescent stellate cells contain a very low level of this mRNA, but treatment of the cells with Actinomycin D or cycloheximide increases the mRNA accumulation 5 fold in 3 hours. The same treatment has no effect on activated stellate cells, which produce a large amount of the collagen alpha 1(I) mRNA. This suggests that there is a labile degrading activity which normally prevents accumulation of the mRNA in quiescent cells. Half life of the mRNA in activated cells is about 48 hours. We detected a sequence specific RNA binding activity present in these cells which binds to the C-rich sequence in the 3' UTR of collagen mRNA. Such binding can not be detected in quiescent cells and may be responsible for the stabilization of the mRNA in activated stellate cells. Thus, collagen alpha 1(I) mRNA levels in stellate cells may be modulated by negative regulation in quiescent cells and by positive regulation in activated cells.