Activation of NF-kappa B by double-stranded RNA (dsRNA) in the absence of protein kinase R and RNase L demonstrates the existence of two separate dsRNA-triggered antiviral programs

Double-stranded RNA (dsRNA) of viral origin triggers two programs of the in nate immunity in virus-infected cells. One is intended to decrease the rate of host cell protein synthesis and thus to prevent viral replication. This program is mediated by protein kinase R (PKR) and by RNase L and contribut es, eventually, to the self elimination of the infected cell via apoptosis. The second program is responsible for the production of antiviral (type I) interferons and other alarmone cytokines and serves the purpose of prepari ng naive cells for the viral invasion, This second program requires the sur vival of the infected cell and depends on the expression of antiapoptotic g enes through the activation of the NF-KB transcription factor. The second p rogram therefore relies on ongoing transcription and translation. It has be en proposed that PKR plays an essential role in the activation of NF-KB by dsRNA. Here we present evidence that the dsRNA-induced NF-KB activity and t he expression of beta interferon and inflammatory cytokines do not require either PKR or RNase L. Our results indicate, therefore, that the two dsRNA- activated programs are separate and can function independently of each othe r.