Activation of NF-κB 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

Abstract

Double-stranded RNA (dsRNA) of viral origin triggers two programs of the innate 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 contributes, 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 preparing naive cells for the viral invasion. This second program requires the survival of the infected cell and depends on the expression of antiapoptotic genes through the activation of the NF-κB transcription factor. The second program therefore relies on ongoing transcription and translation. It has been proposed that PKR plays an essential role in the activation of NF-κB by dsRNA. Here we present evidence that the dsRNA-induced NF-κB activity and the 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 other.

ACKNOWLEDGMENTS

We thank Olga Ryabinina, Thanh-Hoai Dinh, and Paul Spitz for excellent technical assistance. We thank Bryan Williams for the pkr^+/+(EX2+3) andpkr^0/0 (EX2+3) MEF and Robert Silverman for the rnasel^+/+‖pkr^+/+ , rnasel^−/−‖pkr^+/+ , andrnasel^−/−‖pkr^−/− 3T3-like fibroblasts and for the EMCV.

This work was supported by U.S. Public Health Service grants CA-39360 and ES-08456 to B.E.M. and by an N. L. Tartar Research Fund Fellowship to M.S.I. J.C.B. is supported by the National Cancer Institute of Canada and the Canadian Cancer Society.