Multiple Targets for Suppression of RNA Interference by Tomato Aspermy Virus Protein 2B

Viral suppressors of RNA interference (RNAi) appear to have evolved as a response to this innate genomic defense. We report the nucleic acid binding properties of the Cucumovirus RNAi suppressor tomato aspermy virus protein 2B (TAV 213). Using total internal reflection fluorescence spectroscopy (TIRFS), we show that TAV 2B binds double-stranded RNA corresponding to siRNAs and miRNAs, as well as single-stranded RNA oligonucleotides. A number of positively charged residues between amino acids 20 and 30 are critical for RNA binding. Binding to RNA oligomerizes and induces a conformational change in TAV 213, causing it to form a primarily helical structure and a 4:2 protein-RNA complex.