Identification and transcriptional analysis of a 3'-coterminal gene cluster containing UL1, UL2, UL3, and UL3.5 open reading frames of bovine herpesvirus-1.

We have identified and sequenced 3113 nucleotides located at the right end of the HindIII L fragment of the bovine herpesvirus-1 genome from map units 0.712 to 0.734. Analysis of the sequence identified four open reading frames (ORFs) which are designated UL1, UL2, UL3, and UL3.5 based on their homology with proteins of herpes simplex virus-1 (HSV-1), pseudorabies virus (PRV), equine herpesvirus-1, and varicella-zoster virus. The UL1 ORF of 158 amino acids exhibits limited homology with UL1 (glycoprotein gL) of HSV-1 (27%) and PRV (21%). The UL2 ORF of 204 amino acids shows significant homology to UL2 (uracil-DNA glycosylase) of HSV-1 (68%) and PRV (75%). The UL3 ORF of 204 amino acids shows significant homology to UL3 (nuclear phosphoprotein) of HSV-1 (62%) and PRV (53%). The UL3.5 ORF of 126 amino acids shows limited homology to the UL3.5 ORF of PRV (31%). The homolog of this gene is absent in HSV-1. Nucleotide sequence analyses also revealed potential TATA boxes located upstream of each ORF. However, only one polyadenylation signal was detected downstream of the UL3.5 ORF. Northern (RNA) blot analyses revealed four transcripts of 2.4, 1.9, 1.3, and 0.7 kb, which are transcribed in the same direction and are 3'-coterminal transcripts. These mRNAs appear to yield proteins encoded by UL1 (2.4 kb), UL2 (1.9 kb), UL3 (1.3 kb), and UL3.5 (0.7 kb) ORFs.