Caister Academic Press

Dissecting the Assembly Pathway of Bacterial dsRNA Viruses: Infectious Nucleocapsids Produced by Self-Assembly

Minna M. Poranen, Roman Tuma and Dennis H. Bamford
from: Segmented Double-stranded RNA Viruses: Structure and Molecular Biology (Edited by: John T. Patton). Caister Academic Press, U.K. (2008)


The virions of double-stranded RNA bacteriophages of the family Cystoviridae possess a triple-layered structure surrounding the tri-segmented genome. Genome-containing double-shelled nucleocapsids are formed by a self-assembly process that can be accomplished in vitro using purified proteins and RNA constituents. The assembly process involves formation of empty particles, which package single-stranded genomic precursor RNA molecules. Subsequently, the precursor RNA molecules are replicated into the double-stranded form within the particle. Finally, the genome-containing particles acquire the nucleocapsid surface shell. Two viral enzymes, the packaging NTPase P4 and the polymerase P2, are part of the assembly process. The assembly of the inner protein capsid involves tetramerization of the major capsid protein P1 and subsequent interaction with the enzymatic components (P2 and P4). The in vitro reconstituted Φ6 nucleocapsids can penetrate the host cell plasma membrane and initiate a productive infection cycle read more ...
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