MUTATIONAL ANALYSIS OF THE HERPES-SIMPLEX VIRUS TYPE-1 STRICT LATE UL38 PROMOTER LEADER REVEALS 2 REGIONS CRITICAL IN TRANSCRIPTIONAL REGULATION

The unusual TATA homology TTTAAA at -31 relative to the transcriptiona l start site of the herpes simplex virus type 1 (HSV-1) strict late (g amma) U(L)38 gene defines the 5' extent of this promoter in recombinan t virus. We have further analyzed this promoter by generating recombin ant viruses containing nested deletions 3' of the transcriptional star t site and with recombinant viruses containing specific promoter/leade r alterations. A recombinant virus containing the U(L)38 promoter/lead er from -50 to +9 expressed reporter gene enzyme levels at approximate ly 10% of those from a recombinant containing the full viral promoter/ leader (-50 to +99). The accumulation of reporter gene mRNA in infecti ons with the -50 to +9 recombinant was still regulated with gamma kine tics. Further removal of U(L)38 leader sequences resulted in a nearly complete loss of expression. Analysis of promoter chimera recombinant viruses has shown that sequences downstream of the TATA box and spanni ng the transcriptional start site of the U(L)38 promoter are functiona lly distinct from those of either the beta U(L)37 gene or the betagamm a VP16 (U(L)48) gene; thus, we conclude that sequences from -31 to +9 of the U(L)38 gene constitute a core gamma promoter. Further deletiona l and substitutional analyses have also demonstrated the presence of a 14-bp element (the downstream activation sequence) located between +2 0 to +33 in the nontranslated leader region which is required for full levels of transcription.