The proteins expressed by different isolates ofDrosophila C virus

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Abstract
Isolates ofDrosophila C virus (DCV) fromDrosophila flies obtained in geographically different regions were adapted to growth inDrosophila tissue culture cells. The viruses, purified from tissue culture cells, were shown to be serologically related to one of the isolates (“O” from Ouarzazate, morocco). Analysis of the structural proteins by polyacrylamide gel electrophoresis demonstrated differences between the isolates. Labelling intracellular proteins of infectedDrosophila melanogaster cells with35S-methionine at 28° C demonstrated the presence of the virus structural proteins and their immediate precursors. Raising the temperature to 37° C both before and during the pulse period inhibited the processing of the high molecular weight proteins and resulted in a greater “shut-off” of host cell proteins than viral induced proteins. This allowed the precursor proteins to be compared as well as the structural proteins of the different strains. It was possible to clearly distinguish differences between the isolates on the basis of the induced proteins, although limited proteolysis of corresponding proteins showed marked similarities. Hence it is possible to distinguish between different isolates of the “same” small RNA-virus of insects from geographically different regions.