Nucleotide sequence of the pseudorabies virus immediate early gene, encoding a strong transactivator protein

We report the complete DNA sequence of teh pseudorabies virus (PRV) immediate early (IE) gene and its flanking nucleotide sequences, together comprising 5091 base pairs. An open reading frame starts with an ATG codon in position 263 from the transcription-initiation site and ends with a TGA codon in position 4601, thus encoding a predicted protein of 1446 amino acids (150 kD). The PRV IE protein exhibits significant homology with the functionally related transactivator proteins, ICP4 of herpes simplex virus-1 (HSV-1) and p140 of varicella zoster virus (VZV). The extent of homology varies widely along the three sequences: Two regions of the PRV IE protein extending from amino acids 482 to 659 and 959 to 1350 exhibit 50% to 60% identity with the cognate sequences, whereas the remaining sequence reveals little homology apart from a common polyserine stretch. The base composition of the PRV IE coding region is 80% G + C, compared with 81.5% for HSV-1 and 64.1% for VZV. Yet the PRV IE protein appears to be as closely related to VZV p140 as to HSV-1 ICP4. The regions of strong homology are also apparent in plots predicting secondary structure.