Heat inactivation of vaccinia virus particle-associated functions: properties of heated particles in vivo and in vitro.

The heat inactivation characteristics of several vaccinia virus particle-associated functions known to be involved in the transcription of the genome were examined. All functions were more resistant to heat than infectivity. Noninfectious particles were generated which exhibited significant levels of activity of all enzymes examined, and their properties were investigaed both in vitro and in vivo. RNA was synthesized in vitro by such particles, although transport of the RNA into the surrounding medium was defective. This RNA was larger than that made in normal particles but it was polyadenylated and functioned in vitro as a message coding for normal early proteins. The sequences transcribed were similar to those transcribed in normal particles, and we suggest that the production of abnormally large RNA is due to a defect in transcriptional termination. We could not detect any virus-specific protein or RNA synthesis in cells exposed to these inactivated particles and conclude that the loss of infectivity caused by heating is due to a general decline in the activities of a number of particle functions.