Regulation of murine cytomegalovirus gene expression. I. Transcription during productive infection.

Murine cytomegalovirus RNA synthesis in productively infected mouse embryo cultures was measured by reassociation kinetics with iodinated viral DNA. The data were analyzed by a computer program and indicated the following: before DNA replication approximately 25% of the genome was transcribed into asymmetric transcripts, of which slightly fewer than half of the sequences were recovered from the cytoplasm. After viral DNA replication, approximately 38% of the genome was transcribed (5% as symmetric transcripts), and again less than half of the sequences appeared in the cytoplasm. Both early and late RNA comprised two abundance classes differing about 8- to 10-fold in concentration. Early RNA was a subset of late RNA. The RNE sequences synthesized in late-infected cells in the presence of cytosine arabinoside or cycloheximide were similar to early RNA. Thus, murine cytomegalovirus displays temporal, quantitative, and post-transcriptional controls over gene expression, but the pattern differs considerably from herpes simplex virus.