High-resolution characterization of herpes simplex virus type 1 transcripts encoding alkaline exonuclease and a 50,000-dalton protein tentatively identified as a capsid protein.

Four partially overlapping mRNAs (1.9, 2.3, 3.9, and 4.5 kilobases [kb]) were located between 0.16 and 0.19 map units on the herpes simplex virus type 1 genome. Their direction of transcription was found to be from right to left. The 2.3-kb mRNA was found to be early (beta), whereas the others were late (beta gamma). Partial sequence analysis of the DNA encoding these genes indicated that the promoter for the 2.3-kb mRNA shares structural features with other early (beta) promoters. In vitro translation of hybrid-selected mRNA indicated that among the proteins these mRNAs encode are an 82,000-dalton (d) polypeptide reactive with a monoclonal antibody against herpes simplex virus type 2 alkaline exonuclease and a 50,000-d polypeptide weakly reactive with a polyclonal antibody made against the capsid protein VP19C. Further experiments suggested that the 2.3-kb mRNA encodes the 82,000-d polypeptide, whereas one (or both) of the larger mRNAs encodes the 50,000-d protein. A novel finding was that the 1.9-kb mRNA appears to share part of the translational reading frame for alkaline exonuclease, but any polypeptide it encodes does not react with the monoclonal antibody to this enzyme.