VPg-mediated Aggregation of Potyviral RNA

1 Department of Plant Pathology and 2 Department of Biochemistry, University of Kentucky, Lexington, Kentucky 40546, U.S.A. RNA prepared from the potyvirus tobacco vein mottling virus contained aggregates of the 9.5 kb genomic RNA with electrophoretic mobilities corresponding to 20 and 41 kb species. Similar aggregates were present in preparations of the RNAs of two other potyviruses. Aggregation occurred during or after purification of the RNA by sucrose gradient centrifugation and alcohol precipitation and was dependent upon the presence of a protein apparently bound covalently to a region at or near the 5' terminus of the viral RNA. This protein is probably the VPg. The RNAs of tobacco mosaic virus and cowpea mosaic virus did not form aggregates when isolated from purified virus by similar procedures. Received 11 July 1990; accepted 16 October 1990.