Stabilization of Interferon Messenger RNA Activity by Treatment of Cells with Metabolic Inhibitors and Lowering of the Incubation Temperature

Interferon production was induced in a strain of human diploid foreskin cells with poly(I).poly(C). Cycloheximide was included in the culture medium at the time of addition of the inducer. Actinomycin D was added to the cultures 4 or 5 hr later, before the inhibition of protein synthesis was reversed at 6 hr. Thus, subsequent interferon synthesis had to be directed by messenger RNA synthesized before addition of actinomycin D. The amount of interferon produced after such treatment was about 50-fold greater than in cells induced with poly(I).poly(C) but not treated with inhibitors. Experiments using cordycepin suggested that in spite of the continued presence of the inducer the synthesis of the bulk of interferon messenger RNA was completed within the first 2 hr of exposure of cells to poly(I).poly(C) and cycloheximide. Transcription of interferon messenger RNA was apparently not affected when interferon synthesis was suppressed to various degrees by different inhibitors of protein synthesis, indicating the independence of transcription and translation. The high rate of interferon synthesis after the reversal of cycloheximide action was more sustained at 32 degrees than at 37 degrees . The rate of decrease of overall protein synthesis in cells treated with actinomycin D and then incubated either at 32 degrees or 37 degrees showed a similar dependence on incubation temperature, suggesting that the stability of messenger RNA (or of another actinomycin D-sensitive component required for protein synthesis) was greater at the lower temperature.