Biogenesis of poxviruses: analysis of the morphogenetic sequence using a conditional lethal mutant defective in envelope self-assembly.

A conditional lethal, temperature-sensitive mutant of vaccinia, defective in assembly of the virus envelope and maturation, was characterized and shown to mimic exactly the aberrations produced by rifampicin. Analyses of the infection at restrictive and permissive temperatures were conducted with electron microscopy, isotopic pulse-chase experiments in which polypeptides were separated by polyacrylamide slab gels, and assays of core enzymatic activities. The data collected by several approaches reveal that assembly and maturation of vaccinia involves a tightly coupled sequence of interrelated events including the assembly of the envelope, post-translational cleavage of several virion polypeptides, and induction of the core enzymes.