SYNTHESIS AND PROCESSING OF THE RUBELLA-VIRUS P110 POLYPROTEIN PRECURSOR IN BACULOVIRUS-INFECTED SPODOPTERA-FRUGIPERDA CELLS

In order to study the processing of rubella virus (RV) structural prot eins (capsid protein, of 33 kDa; E2 of 42-47 kDa; and E1 of 58 kDa) in Spodoptera frugiperda (fall armyworm) cells, a 24S cDNA encoding the polyprotein precursor, p110, was inserted under the transcriptional re gulation of the polyhedrin gene promoter of the Autographa californica nuclear polyhedrosis virus (AcNPV) and expressed during viral infecti on. By immunoblot analysis using antibodies directed against whole RV and the individual structural proteins, evidence is presented that pol ypeptides similar to those synthesized in RV-infected B-Vero cells are expressed in this lepidopteran insect cell line infected with the rec ombinant baculovirus, VL1392-RV24S. The identity of the recombinant pr oteins was further confirmed using human convalescent sera. By express ing the recombinant proteins in the presence and absence of tunicamyci n, we have further demonstrated that the 248 transcription-translation unit of RV, is expressed and proteolytically cleaved similarly, if no t identically, in Sf9 cells as compared to B-Vero cells.