THE HERPESVIRUS SAIMIRI ORF50 GENE, ENCODING A TRANSCRIPTIONAL ACTIVATOR HOMOLOGOUS TO THE EPSTEIN-BARR-VIRUS R PROTEIN, IS TRANSCRIBED FROM 2 DISTINCT PROMOTERS OF DIFFERENT TEMPORAL PHASES

The mRNA species encoding the herpesvirus saimiri (HVS) homolog of the Epstein-Barr virus R transcriptional activator (termed ORF50) have be en identified and used to determine transcriptional start sites within the gene. The first transcript is spliced and starts from a promoter within ORF49 containing a single intron; the second is produced from a promoter within the second exon and is in the same reading frame. The spliced transcript is detected at early times during productive virus replication in OMK cells, whereas the nonspliced transcript is detect ed later. The spliced transcript is fivefold-more potent in activating the delayed-early ORF6 promoter; the function of the nonspliced trans cript is unclear. Thus, the role of this protein in activating herpesv irus saimiri from the latent state may differ significantly from that of the Epstein-Barr virus R protein.