Analysis of DNA sequences which regulate the transcription of a herpes simplex virus immediate early gene

The locations and functions of DNA sequences involved in transcription of the gene encoding herpes simplex virus type 1 immediate early (IE) mRNAs 4 and 5 were analyzed by use of a transient-expression assay. The region upstream of the genes encoding IE mRNAs 4 and 5 was fused to the thymidine kinase gene coding sequences, and production of enzyme or RNA was measured after transfection of plasmids into BHK cells. The effect of deletions in the upstream region was determined in the absence or presence of a virus structural component which stimulates herpes simplex virus IE transcription. Two distinct units were identified. One of these was a promoter which required not more than 69 base pairs of DNA specific for the genes encoding IE mRNAs 4 and 5 upstream from the mRNA 5' terminus. The other was a far-upstream region which mediated the response to the virion component and had an upstream boundary between nucleotides -347 and -335. An origin of DNA replication was interposed between these two units. The element TAATGAGATAC , which represents a consensus sequence present in the upstream regions of all herpes simplex type 1 IE genes, appeared to be essential for stimulation by the virion component. The activity of this element was modulated by the sequences which flank it, especially by regions having extremely high contents of guanine plus cytosine and which contain a conserved unit CCCGCCC or its complement GGGCGGG .