Expression and functional characterization of classical swine fever virus Erns protein

Erns is an envelope glycoprotein of classical swine fever virus (CSFV) with unusual RNase activity. Recently, Erns was found to have a new function of counteracting the β-interferon (IFN-β) induction pathway. In this study, wildtype ErnsSM and two mutated Erns proteins ErnsH297k and ErnsH346k were expressed in insect cells and purified for RNase activity and function analysis. RNase activity assay in vitro demonstrated that only wildtype Erns protein had RNase activity. However, both wildtype ErnsSM and the two mutated ErnsErnsH297k and ErnsH346k as exogenous proteins had a block effect on Newcastle disease virus (NDV)-mediated IFN-β promoter induction.