Cell-free Translation of Cricket Paralysis Virus RNA: Analysis of the Synthesis and Processing of Virus-specified Proteins

Translation of cricket paralysis virus (CrPV) RNA in a rabbit reticulocyte lysate yielded proteins which co-migrate on polyacrylamide gels with the structural proteins VP 1 and VP3. These proteins were identified by partial proteolysis and a number of high mol. wt, proteins were shown to be precursors of the structural proteins. The third structural protein VP2 was not identified in vitro but was shown to be formed in vivo from the minor 'structural' protein VP0. The profile of high mol. wt. proteins in vitro differed from those found in infected cells, but processing was similar with precursors being cleaved sequentially to give a group of proteins with mol. wt. of 50000 to 63 000. Processing proceeded in vitro to give VP1 and VP3 but synthesis of VP2 and its immediate precursor VP0 was not apparent. This is consistent with an inhibition of synthesis of VP0 found in infected cells treated with iodoacetamide and suggests that CrPV utilizes a different mechanism for the synthesis of VP0 and VP2 than it does for VP1 and VP3. A tentative model for the processing of CrPV-specified proteins is proposed.