INFLUENCE OF MEDIUM HYPEROSMOLARITY AND OF GUANIDINE ON THE SYNTHESIS AND PROCESSING OF POLIOVIRUS PROTEINS

Abstract

Although it is generally accepted that all poliovirus specific proteins synthesized in infected cells are derived from one primary translation product, the poliovirus polyprotein (Jacobson & Baltimore, 1968), pulse labeling with 35 S-methionine of poliovirus infected cells under conditions of restricted polypeptide chain initiation leads to the accumulation of viral proteins in ratios different from those found under normal conditions. The accumulation of viral proteins coded for by the 5′ part of the viral mRNA (NCVP1a and its cleavage products) is twofold more inhibited by increased medium osmolarity than the accumulation of the other viral proteins notably NCVPx and NCVP1b and NCVP2. In addition, we have observed that the first virus specific proteins which appear during the replication cycle of polioviruses are NCVPx, NCVP1b and NCVP2. NCVP1a is only detectable at later times in infection. Therefore we propose that either NCVP1a is preferentially degraded early in infection or when cells are incubated in medium with increased osmolarity or that viral protein synthesis is initiated at more than one site. The presence of guanidine in the growth medium during the early part of the replication cycle results in dramatic alterations in the labeling pattern of poliovirus proteins indicating that guanidine affects the processing of viral proteins. Altered processing might be the cause for the inhibition of viral RNA synthesis.