INDUCTION AND REGULATION OF THE 26-KDA PROTEIN IN THE ABSENCE OF SYNTHESIS OF BETA-INTERFERON MESSENGER-RNA IN HUMAN-CELLS

The expression of the gene coding for the 26-kDA [kilodalton] protein coinduced with human .beta.-interferon (HuIFN-.beta.) in human fibroblast was measured by cytoplasmic dot hybridization in WISH cells. The production of the 26-kDa-protein mRNA is not induced by poly(I).cntdot.poly(C) but maximally induced by cycloheximide alone. HuIFN-.beta. is induced by poly(I) .cntdot. poly(C) and not by cycloheximide. WISH cells showed in addition a low constitutive level of 26-kDa-protein mRNA prior to induction. These results were confirmed by sizing the RNA by Northern blot analysis. Pretreatment with partially purified or pure IFN-.beta. has only a slight effect on 26-kDa protein mRNA production. The kinetics of induction and the amount of inducer required for an optimal induction of the 26-kDa-protein mRNA in WISH cells were determined. This mRNA was thus maximally induced in WISH cells in the absence of detectable IFN-.beta.; it represents about 0.05% of poly(A)-rich mRNA in cycloheximide-induced WISH cells. The 26-kDa-protein does not share the general characteristics of interferons. Evidently, HuIFN-.beta. and the 26-kDa-protein genes are differently regulated.