Expression of a herpes simplex virus 1 open reading frame antisense to the gamma(1)34.5 gene and transcribed by an RNA 3' coterminal with the unspliced latency-associated transcript.

Sensory neurons harboring latent herpes simplex virus 1 express viral RNAs derived from one or more transcriptional units contained in the inverted repeats which flank the long unique sequence but which terminate in the inverted repeats flanking the small unique sequences of viral DNA. These transcripts are also made in productively infected cells. We have identified 16 potential open reading frames (ORFs) predicted to encode 50 or more codons within the domain of the largest reported unspliced transcript and examined 5 ORFs by in-frame insertion of a sequence encoding an epitope reacting with a monoclonal antibody against a human cytomegalovirus protein. One ORF (ORF P), coincident with but antisense to the gamma(1)34.5 gene, was expressed but only under conditions in which ICP4 was not functional. To ensure the authenticity of the expression, a second degenerate sequence encoding the same epitope was inserted into a distant site of the same ORF. The protein expressed by the ORF P with two insertions migrated more slowly than the one carrying one insertion only, indicating that ORF P is expressed.