REOVIRUS GENOME SEGMENT ASSORTMENT INTO PROGENY GENOMES STUDIED BY THE USE OF MONOCLONAL-ANTIBODIES DIRECTED AGAINST REOVIRUS PROTEINS

Using a panel of monoclonal antibodies (MABs) against reovirus proteins, we have identified proteins that associate with reovirus messenger RNA molecules prior to the generation of progeny double-stranded (ds) genome segments and proteins that are components of the structures within which progeny ds genome segments are generated. The following conclusions can be drawn from the results obtained. (1) Three proteins rapidly become associated with mRNA molecules to form single-stranded RNA-containing complexes (ssRCCs): the nonstructural protein μNS, the nonstructural protein σNS, and protein σ3. (2) Analysis of populations of ssRCCs in density gradients and by sequential exposure to various MABs indicates that some ssRCCs contain only μNS, others μNS and uNS or σ3, and others all three proteins. Each ssRCC contains one RNA molecule and, depending on the size of the RNA, 10-30 protein molecules. (3) The relative proportions of the individual RNA species in the ssRCC populations reflect the composition of the total mRNA population present in infected cells (which differs substantially from equimolarity). (4) RCCs that contain dsRNA, which become detectable as early as 4 hr after infection, contain not only μNS, σNS, and σ3, but also λ2. (5) The relative proportions of the 10 genome segments in dsRCCs are equimolar. This suggests that genome segment assortment into progeny genomes is linked to the transcription of plus strands into minus strands. © 1992.