2 OVERLAPPING TRANSCRIPTION UNITS WHICH EXTEND ACROSS THE L-S JUNCTION OF HERPES-SIMPLEX VIRUS TYPE-1

A region of the herpes simplex virus type 1 genome located upstream of the alpha 0 promoter contains a promoter which regulates transcriptio n in the opposite orientation to that driven by alpha 0. Analyses of m utants from which this promoter, alpha X, was deleted and a mutant in which a fragment that serves as a transcription terminator and polyade nylation signal was inserted upstream of this promoter demonstrate tha t two distinct transcription units overlap this region of the genome a nd are transcribed in a direction antisense to the neurovirulence gene gamma(1)34.5. One unit, dependent on the alpha X promoter, is active when cells are infected in the presence of the protein synthesis inhib itor cycloheximide. The second unit, independent of alpha X, is active during the course of productive infection. This transcription unit or iginates from a promoter upstream of alpha X which is distinct from th e latency associated promoter (LAP). Two polyadenylated transcripts of 0.9 and 4.9 kh accumulate from this region of the genome during produ ctive infection, but no mature transcripts accumulate in infected cell s maintained in the presence of cycloheximide. Kinetic analyses demons trate that the transcripts that accumulate during productive infection fall into the beta class of herpes simplex virus type 1 genes.