Abstract
The structure and precise map location of the 4.1-kb herpes simplex virus type 1 (HSV-1) immediate-early mRNA (IE mRNA-3) that encodes a regulatory polypeptide, with an approximate mol. wt. of 175 000, has been determined. Nuclease S1 digestion procedures using labelled virus DNA probes have shown that IE mRNA-3 is unspliced and maps entirely within the TRs/IRs genome regions. DNA sequences at the 5' and 3' ends of IE mRNA-3 have been examined and regulatory signals involved in initiation of transcription and polyadenylation have been identified. No other mRNA is known to map within the region coding for IE mRNA-3.