Involvement of structural and nonstructural polypeptides on rotavirus RNA synthesis.

Rotavirus are segmented double stranded RNA viruses with a double protein capsid around a central core. The virus replicates in the cell cytoplasm. After infection, eleven mRNAs are transcribed from the viral genome. To characterize further the infection cycle, viral polypeptide synthesis and RNA replication were studied using labelled precursors. The involvement of nonstructural polypeptides NS34 and NS35 was determined by the kinetics of the appearance of viral polypeptides in infected cells. Experiments in which cycloheximide was used showed that the synthesis of both polypeptides was required to begin RNA replication. The isolation of subviral particles at 8 hours postinfection indicates that there is a particle containing the nonstructural polypeptides and the structural polypeptides VP1, VP2, and VP6 that seem to be able to transcribe the viral genome to produce other RNA species. The results suggest that there is a core-like particle similar to one obtained in vitro which upon the addition of VP6 is able to transcribe the virus genome. This seems to indicate that core-like particles may alter their specificity for plus or minus RNA synthesis depending upon the polypeptides that interact with it. The interaction between VP6 and the viral core was analyzed by means of antibodies raised against the viral core and VP6. The results suggest that VP6 contains a specific binding site to the core complex and this interaction allows the synthesis of mRNA.