Identification of a protein encoded in the herpes simplex virus type 1 latency associated transcript promoter region

Herpes simplex virus type 1 (HSV-1) establishes a lifelong latency in the neurons of its host. Sporadically, the latent virus reactivates and spreads back to the original site of infection and causes recrudescent diseases. The only gene actively transcribed during neuronal latency is the latency associated transcript (LAT) gene. Several transcripts have been detected in the important LAT promoter region. However, no polypeptides coded by these transcripts are known. In this communication, we reported the cloning, sequencing, and characterization of a transcript immediately upstream of LAT. We designated this gene UOL (Upstream of LAT). The UOL RNA is polyadenylated, expressed as a late gene in infected cells, transcribed in the same direction as LAT, and contains an open reading frame (ORF) capable of encoding a protein of 96 amino acids with a predicted molecular mass of 11 kDa. The UOL transcript contains 466 nucleotides in length. The 5′ end of the UOL transcript starts at nucleotide 118,266 and the 3′ end of the UOL transcript ends at nucleotide 118,731 based on the published 17syn+ genomic sequence. The UOL protein was detected in infected cell lysates by immunoprecipitation using an antibody raised against UOL ORF synthetic peptide. More importantly, sera from mice infected with wild-type HSV-1 but not sera from mice infected with a mutant with the UOL region deleted recognized the UOL ORF, expressed in Escherichia coli, on Western blots. These results suggest that a UOL protein is in HSV-1 infected tissue culture cells and in mice infected with HSV-1.