Characterization of the genes, including that encoding the viral proteinase, contained in BamHI restriction fragment 9 of the pseudorabies virus genome.

We describe the nucleotide sequence, transcription pattern and open reading frames (ORFs) located on BamHI restriction fragment 9 (0.406-0.435 map units) in the unique long segment of the pseudorabies virus (PRV) genome. The fragment contains three nested genes with a common 3' end. The 5' ends of the corresponding 0.9, 1.7 and 3.3 kb mRNAs have been mapped. Fragment BamHI-9 contains three complete ORFs, ORF1, ORF2 and ORF2.5. ORF1, which is within the 3.3 kb transcript, encodes a protein with an apparent molecular mass of 60 kDa which is homologous to the product of the herpes simplex virus type 1 UL25 gene. The 1.7 kb mRNA contains ORF2, whose product is homologous to the herpesvirus proteinases, while the 0.9 kb transcript contains ORF2.5, which probably encodes the assembly protein precursor. ORF2 was identified as the PRV proteinase gene following expression in E. coli, using the product of ORF2.5 as the substrate protein.