A detailed analysis of an HSV-1 early promoter: sequences involved in trans-activation by viral immediate-early gene products are not early-gene specific

This report describes a detailed analysis of the functional DNA sequences within the HSV-1 glycoprotein D gene promoter. The transcriptional activity of deletion and insertion promoter mutants was studied after both trans activation, mediated by viral products, and cis activation by a linked SV40 enhancer. Two G-rich areas (upstream of a TATA signal) were identified as important regions of the promoter. These “upstream” signals were active in both orientations. A functional TATA-box region was detected. A second region, not homologous to the concensus TATA sequence, also appeared to have a role in the positioning of the RNA cap-sites, which included both purine and pyrimidine 5′ ends. Deletion of the cap-site region resulted in a moderate reduction in transcription. All the promoter elements were important for both cis and trans activated transcription. No sequence specific for viral (trans) regulation was detected, implying that Early promoters are not distinguished by specific sequences. Since HSV-1 and some other animal viruses can activate transcription from unrelated promoters, this process is probably non-specific and applicable to many, particularly extra-chromosomal, genes. The possible mechanisms of this activation are discussed