Synthesis of reovirus double-stranded RNA within virionlike particles

Abstract

The enzyme responsible for the synthesis of reovirus double-stranded RNA (SS → DS RNA polymerase) and its double-stranded RNA product synthesized in vitro were investigated. They were studied by determining (1) the sedimentation pattern of SS → DS RNA polymerase in cesium chloride and sucrose density gradients; (2) the sedimentation pattern of the SS → DS RNA polymerase product under nondenaturing conditions in CsCl and sucrose density gradients and (3) the response of SS → DS RNA polymerase activity and its nondenatured product to treatment with chymotrypsin. SS → DS RNA polymerase activity is associated with particles which sediment in sucrose density gradients slightly slower than virions, have a density in CsCl of 1.34 g/ml as compared with 1.36 g/ml for virions and which are converted to particles with a density of 1.43 g/ml in CsCl after treatment with chymotrypsin. Double-stranded RNA synthesized by these particles in vitro is not released but remains associated with them. These results suggest that double-stranded RNA is synthesized in a viruslike particle consisting of a corelike structure to the outside of which additional protein molecules are attached.