RNA/protein interactions in icosahedral virus assembly

Abstract

The pathway of icosahedral viral assembly is a poorly understood process. In this review we examine three model systems in which icosahedral viral assembly is initiated by the viral RNA. Bacteriophage R17, and the plant viruses turnip crinkle and cowpea chlorotic mottle virus have emerged as model systems because they combine biochemical, molecular and structural approaches to addressing assembly questions. In all three systems it is suggested that binding of capsid protein(s) to a specific RNA structure forms an assembly initiation complex which nucleates the subsequent addition of capsid protein subunits to form the completed shell. Detailed structures are not emerging on the initiation complex and the completed virus particle, but much remains to be learned about the process which leads from one to the other.