Localization of host poly(A)+ mRNA in the ribosome profile of mengovirus-infected Ehrlich ascites tumor cells

The distribution of poly(A)⁺ mRNA among polysomes, monosomes, and ribosome-free supernatant fractions after mengovirus infection of Ehrlich ascites tumor (EAT) cells was investigated employing sucrose gradient centrifugation of their corresponding postnuclear supernatants. Poly(A)⁺ mRNA was isolated from sucrose gradient fractions and quantitated in a cell-free protein synthesizing system from uninfected EAT cells. It was also localized by annealing [³H]-poly(U) to the poly(A)-tracts of mRNA present in the sucrose gradient fractions. Both experiments revealed a gradual shift of host poly(A)⁺ mRNA from large to small polysomes and monosomes, respectively, with the time postinfection. The greatest part of host template RNA appears to remain ribosome-bound and only a fraction seems to be detached from the ribosomes in the course of mengovirus infection. At the end of the infectious cycle, 8 h postinfection, approximately 70% of the poly(A)⁺ mRNA detected in uninfected cells is still biologically active, but not translated in vivo, in agreement with data from the [³H] poly(U) hybridization experiment.