A RNA virus overcomes 2’,5’-oligoadenylate synthetase-ribonuclease L pathway

Many viruses have evolved diverse mechanisms to defeat cellular interferon systems. Mouse hepatitis virus (MHV), a positive strand RNA virus, inhibits the OAS RNase L pathway by a unique strategy. MHV produces an accessory protein, ns2 that has a phosphodiesterase activity. Basically, phosphodiester bond connects phosphate group between bases of nucleic acids such as DNA and RNA. MHV ns2, by using its phosphodiesterase activity, cleaves the bond of 2’,5’-oligoadenylates (2-5A) that is synthesized by OAS in case of antiviral state stimulated by interferon, which results in the decrease of the amount of 2-5A that is essential for the functional RNase L. Thus, MHV efficiently overcomes the RNase L attack by using its accessory protein.