Synthesis of Drosophila X virus proteins in cultured Drosophila cells.
The genome of Drosophila X virus (DXV) is made up of two segments of dsRNA with molecular weights of 2.3 X 10(6) (A) and 2.2 X 10(6) (B). Agarose gel electrophoresis of RNA fragments produced by S1 nuclease digestion of partially denatured, purified segment A and B indicated that the two genome segments have different nucleotide sequences. The dose-response curve of virus infectivity was linear, indicating that the two genome segments reside in the same particle. The virions contained five polypeptides (VPs) that fell into three molecular weight size classes; large, 110K; medium, 49K and 45K; and small, 34K and 27K. Virus infection of Drosophila cells induced the synthesis of five infected cell polypeptides (ICPs); 110K, 67K, 49K, 34K, and 27K. Pulse-chase experiments and peptide mapping revealed that four of these (110K, 67K, 34K, and 27K) were primary gene products and that ICP 49 was generated by post-translational cleavage of ICP 67. The major capsid protein, VP 45, was cleaved from ICP 49; however, this cleavage was incomplete because both polypeptides were present in purified virus. The results suggest that the strategy for protein synthesis of DXV differs from that of other dsRNA viruses.
Nagy
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Veterinary Medical Research Institute, Hungarian Academy of Sciences, Budapest 1581, P.O.B. 18, Hungary.
Dobos
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