Poliovirus Assembly and Encapsidation of Genomic RNA

Abstract

Publisher Summary The cumulative information from poliovirus morphogenetic studies has resulted in a hypothetical pathway for assembly. The proposed steps of assembly include ordered proteolytic cleavages and formation of capsid protein subviral particles prior to RNA encapsidation and maturation of the virion. The three-dimensional structure of poliovirus provided few clues of its interaction, as the encapsidated RNA molecule does not adopt the icosahedral symmetry of the capsid shell. Because the VPg-linked RNA molecules exist in multiple conformations within a crystal lattice of poliovirus virions, structural determinations for the RNA genome and VPg could not be made. It has been reported that portions of the P1 coding region of polio virus contain cis elements required for RNA replication and/or encapsidation of the genome. Another report has demonstrated that sequences at the 5' end of the P1 coding region are dispensable for both RNA replication and encapsidation. These studies demonstrated replication and encapsidation of a poliovirus RNA replicon containing a reporter chloramphenicol acetyltransferase (CAT) gene inserted for part of the P1 gene. The methods to analyze the processes of poliovirus capsid assembly and RNA encapsidation include recombinant vaccinia virus vectors. The systems described offer the dual capability of analyzing P1 capsid precursor cleavage and subviral particle formation separately from the encapsidation step.