Foot-and-mouth disease virus and poliovirus particles contain proteins of the replication complex

Nonstructural proteins 2C, 3CD, 3C, and 3D, and the cellular protein actin, are present in highly purified preparations of foot-and-mouth disease virus (FMDV) and poliovirus. They remain bound in variable amounts to the RNAs when the RNAs are extracted from the viruses,vith phenol or phenol-sodium dodecyl sulfate (SDS) and, for FMDV, when the RNA is released from the particles by a lowering of the pH below 7. RNA prepared by these methods is rapidly degraded at 37 degrees C, particularly in the presence of NH4+ ions, but hydrolysis can be prevented by antibody against Escherichia coli-expressed 3D, indicating that it is the RNA polymerase that has nuclease activity, In contrast, virion RNA from which the nonstructural proteins and actin have been removed by extraction with guanidine thiocyanate-phenol-chloroform or proteinase Ii-phenol is stable at 37 degrees C, although its specific infectivity is lower than that of the RNA extracted with phenol or phenol-SDS. The possible implications of the close association of replication complex proteins with the RNA in virus particles are discussed.