FUNCTIONAL MODULES IMPORTANT FOR ACTIVATED EXPRESSION OF EARLY GENES OF HERPES-SIMPLEX VIRUS TYPE-1 ARE CLUSTERED UPSTREAM OF THE TATA BOX

Functional analysis of two promoters controlling early herpes simplex virus type 1 (HSV-I) transcripts encoding the U(L)37 and U(L)50 (dUTPa se) proteins are described in this report. Transcripts expressed under the control of these promoters were found to be expressed early regar dless of the position of the transcription unit within the viral genom e. Despite this, wt dUTPase mRNA was 6-10 times more abundant than the U(L)37 transcript both in wt and recombinant viruses. This same diffe rence in transcript abundance was seen when a reporter gene (P-galacto sidase) was controlled by the two promoters in recombinant viruses in the heterologous glycoprotein C (gC) locus. Thus, both the kinetics an d relative abundance of U(L)50 and U(L)37 transcripts are a direct fun ction of their respective promoter regulatory elements. Characterizati on of mutated U(L)37 and U(L)50 promoters in recombinant viruses showe d that the functional modules important for expression from these prom oters are concentrated upstream of the transcription start site; howev er the extent and composition of these modules in terms of the cis-act ing elements they contain was different for each. For the U(L)37 promo ter, both a HiNF-P factor binding site (-53 to -58 bp) and the TATA ho mology (-22 to -27) were required for any detectable expression, while an Spl binding site at -123 augmented this but was not absolutely req uired. In contrast, the only functional elements crucial for expressio n from the U(L)50 promoter were the TATA box (-25 to -31) and an Spl b inding site at -117 bp relative to the cap site. Despite differences i n detail, when the functional architecture of these two early promoter s were compared to the extensively characterized HSV-I thymidine kinas e (U(L)23) promoter, class-specific similarities are clearly apparent, (C) 1998 Academic Press.