Processing of cricket paralysis virus induced polypeptides in Drosophila cells: production of high molecular weight polypeptides by treatment with iodoacetamide.

Infection of Drosophila cells with Cricket paralysis virus in the presence of Actinomycin D results in virtual complete inhibition of host cell protein synthesis by four hours post-infection. Using 35S-methionine or 14C-amino acids to pulse infected cells three major classes of viral induced proteins can be detected, (A) high molecular weight precursor proteins, (B) viral structural proteins and (C) low molecular weight cleavage products. The large number of high molecular weight proteins found in the infected cells suggests that a multiple cleavage cascade mechanism is partially utilized to produce virus structural proteins. In infected cells, even with short pulses, the largest viral induced protein obtained has a molecular weight of 144,000. However with pretreatment of the infected cells with iodoacetamide before pulsing, two further proteins are obtained with molecular weights of 205,000 and 190,000. Other changes occur in viral protein precursors in the presence of iodoacetamide.