Purification and properties of murine mammary tumor virus DNA polymerase.

The surface tubule protein p58 was found to be a useful marker to follow vaccinia membrane biogenesis as it is related to virus assembly. Synthesis of p58 does not occur in the absence of DNA replication and is maximal between 8–12 hr postinfection. During normal vaccinia development, p58 as well as other proteins located at or near the surface is among the last components to be integrated into developing particles. Although envelopes can be assembled around immature particles in the absence of DNA and p58 synthesis, combined biochemical and electron microscopic autoradiography studies reveal that such envelopes are either not utilized at all or only inefficiently in the formation of mature virions, once DNA replication has been restored. These observations imply that vaccinia assembly is a tightly coupled process in which internal components are integrated before the completion of the envelope.