AVIAN-SARCOMA VIRUS-RNA SYNTHESIS, RNA SPLICING AND VIRUS PRODUCTION IN HUMAN FORESKIN FIBROBLASTS - EFFECT OF COINFECTION WITH HUMAN CYTOMEGALOVIRUS

The level of RNA transcripts in human foreskin fibroblast (HFF) cells initiated from the avian sarcoma virus (ASV) long terminal repeat (LTR ) promoter was stimulated more than 10-fold when the cells were also i nfected with human cytomegalovirus (HCMV). HCMV was able to stimulate transcription from the ASV LTR promoter even when all the LTR sequence upstream of the TATA box was deleted, suggesting that only the basal LTR promoter is required for the effect. There were no significant cha nges in the ASV RNA splicing pattern in stimulated and unstimulated HF F cells. The mRNAs showing an increase during HCMV stimulation include d aberrantly spliced ASV RNA species as well as unspliced gag-pol. sin gle-spliced env and single-spliced src mRNAs. This pattern was quite d ifferent from ASV splicing in chicken embryo fibroblasts (CEF) but typ ical of that seen in other mammalian cells. A dramatic increase in inf ectious ASV production from the normally non-permissive HFF was correl ated with the increase in amount of ASV RNA in response to HCMV. Thus, there is not an absolute block to ASV production in human cells. Howe ver, infectious ASV production was inefficent in HCMV-stimulated HFF c ompared to that in CEF cells.