Mutational analysis of the dsRNA binding domain of Vaccinia Virus E3 protein

Abstract

Vaccinia virus E3 protein is known to bind double-stranded RNA and mediate interferon resistance. Alanine scanning mutagenesis was performed on its dsRNA binding domain, sufficient for wild-type tropism and immune suppression in vitro, and dsRNA binding and host range function assayed. Residues involved in dsRNA binding were required for host range function; however, seven dsRNA binding mutants were unable to rescue ΔE3L replication. Utilizing recombinant viruses, non-rescue mutants were unable to inhibit protein Kinase R phosphorylation despite dsRNA binding. Furthermore, host range was found to correlate with cytokine suppression and replication in IFN stimulated Huh7R cells. Additionally, no direct association was found between dsRNA binding and PKR interaction, refining the suppression model. Novel protein-protein interactions were discovered between E3 and cellular proteins via differential gel electrophoresis. This study represents the first full mapping of E3 residues involved in dsRNA binding and tropism, forming a basis for future study.