Identification and characterization of RNA-binding activities of avian reovirus non-structural protein sigma NS

Abstract

Cytoplasmic extracts prepared from avian reovirus (ARV) strain S1133-infected chicken embryo fibroblasts were examined for the presence of RNA-binding proteins in order to identify and characterize ARV RNA-binding proteins. Analysis of binding activity to poly(A)Sepharose indicated that infected cells contained significant amounts of a protein that co-migrated with ARV protein sigma NS present in total virus-infected cell extracts. Determination of the N-terminal amino acid sequence of several peptide fragments generated by V8 protease digestion of the poly(A)-Sepharose-purified protein confirmed that this viral protein was sigma NS. Competition assays showed that single-stranded RNA from the unrelated avian pathogen infectious bursal disease virus was able to compete for binding of sigma NS to poly(A)-Sepharose. These data suggest that ARV sigma NS binds to single-stranded RNA in a nucleotide sequence non-specific manner and is functionally similar to its counterpart specified by mammalian reovirus.