The decrease in size and synthetic activity of poliovirus polysomes late in the infectious cycle.

Abstract

Abstract Poliovirus-induced polysomes in infected HeLa cells have been examined during the course of the infectious cycle with respect to (1) sedimentation behavior, (2) the average number of host cell ribosomes per viral messenger RNA molecule, and (3) the spectrum of capsid and noncapsid virus specific polypeptide chains being synthesized. It was found that the polysomes are large (380 S) and indistinguishable in size during most of the RNA replicative cycle. Late in infection, however, the average size of the virus polysomes decreases. The average number of ribosomes in the largest polysomes is about 35 per viral mRNA molecule while in the smaller late-cycle polysomes, which are about 200 S, there are still an average of 20 ribosomes. Furthermore, the rate of protein synthesis per ribosome is considerably decreased in the late cycle polysomes, although the same spectrum of viral proteins is made throughout the replicative cycle.