Avianreovirus mRNAsarenonfunctional ininfected mousecells: Translational basis forvirus host-range restriction

ABSTRACT AvianreovirusS1133penetrates anduncoatsin suspensioncultures ofmouseLcells. The multiplespecies of viral transcripts areproduced in thecytoplasmof theinfected cell, but they fail to associate with polysomes, consistent withthe absence ofviral protein synthesis. Theselective block in avian virus mRNAtranslation is notovercomebycoinfection with mammalianreovirustype3, which replicates in mouse L cells, orbyhypertonicshockorexposuretoalowconcentrationof cycloheximide. Although the avian viral transcripts areinactiveinvivo, RNAextractedfrominfected,nonpermissiveLcells directsthe synthesis ofa normalspectrum ofviral proteins in rabbitreticulocyte lysates. Theseresults indicatethatavian viral transcription is notrestricted in mouse cellsandthatviral replication is prevented at the level of initiation of proteinsynthesis.Avian reoviruses are nearly identical in structure and mo- lecular composition to the well-studied mammalian reovi-ruses (1, 2). Thegenomesofboth consist of10 segments ofdouble-stranded RNA that