Different mechanisms regulate the IFN-inducible expression of 40 kDa human 2'-5' oligo (A) synthetase in HeLa and Molt 4 cells.

Expression of 40 kDa 2'-5' oligo (A) synthetase can serve as a marker of interferon (IFN) activity on the biological target. The mechanisms of induction of human 40 kDa 2'-5' oligo (A) synthetase by IFNs were investigated in HeLa and Molt 4 cells. Using a combined treatment with cycloheximide and actinomycin D we observed that in HeLa cells IFN-alpha did not need ongoing protein synthesis to induce the enzyme, whereas the addition of cycloheximide prevented the induction by IFN-gamma. IFN-alpha induced the 40 kD enzyme in the T-cell line Molt 4 to a level comparable to that in HeLa cells, but only in the presence of active protein synthesis. These results suggest that an early response gene coding for a positive IFN-inducible protein may be needed in T cells, but not in HeLa cells to regulate the transcription of this 2'-5' oligo (A) synthetase gene.