Further characterization of an RNA defective mutant of the foot-and-mouth disease virus.

In this paper a further characterization of a foot-and-mouth disease virus (FMDV) temperature-sensitive mutant, ts 6, is described. This mutant presents a defective RNA synthesis at non-permissive temperature (NPT) by comparison to the wt capacity. However, a low level of viral RNA synthesis (below 10%) was sufficient to achieve an almost normal protein synthesis including a normal pattern of protein cleavage. In addition, morphogenetic precursor particles, 14S and 75S, are formed, indicating that the structural proteins VP0, VP1 and VP3 provide the necessary signal for self-assembly, and that the RNA is not necessary for such assemblage. Finally, although an almost normal synthesis of viral proteins and morphogenetic precursors (14S and 75S) occurs, the induction of cellular protein shut-off was not evident, indicating that this viral effect appears late in the viral cycle once complete viral replication has occurred.