The genomic RNA of Mengovirus II: Comparative analysis of the standard and denser virions

Abstract

The standard Mengovirus particle (buoyant density, 1.34 g/ml) was separated from a denser one (1.44 g/ml) by isopycnic centrifugation in CsCl at pH 8.0. When sedimented through a neutral sucrose density gradient, the standard virions had an apparent sedimention coefficient of 190 S, whereas the denser particles were resolved into two unequal peaks at 220 and 190 S. The denser particles were infectious, and the proportion of denser to standard virions remained unmodified after 24 serial passages at a high m.o.i. The progeny of both the standard and denser particles contained the same relative proportion of standard and denser virions. 32P-labeled RNA extracted from denser particles was degraded to a variable extent. However, all of the big T 1 oligonucleotides characteristic of the standard Mengovirus genome were also present in the fingerprints of the RNA from the denser particles. These two findings suggested that the RNAs of the standard and denser particles were indeed the same, but that the general configuration of the denser virions made their RNA more accessible for interaction with the cesium salt and more susceptible to nuclease degradation. Analysis by SDS-PAGE of the 35S-labeled structural proteins revealed that the denser virions lacked a polypeptide with an apparent MW of 59,000. The remaining polypeptides were present, although their relative proportions were somehow altered. The significance of the denser particles is discussed.