Identification and characterization of an equine herpesvirus 1 late gene encoding a potential zinc finger

In this report, we present the DNA sequence and transcriptional characterization of a gene (IR5) that maps within each of the inverted repeat (IR) segments of the equine herpesvirus type 1 (EHV-1) genome. The IR5 open reading frame (ORF) is located within both IR sequences (nucleotides 9932–10,642 of the IR). DNA sequence analyses of the IR5 gene region revealed an ORF of 236 amino acids (24,793 Da) that showed significant homology to ORF64 of varicella-zoster virus and ORF3 of EHV-4 both of which map within the inverted repeats and to the US10 ORF of herpes simplex virus type 1 (HSV-1) which maps within the unique short segment. Additional analyses of the nucleotide sequence failed to reveal any overlapping ORFs that would correspond to US11 or US12 of HSV-1. Interestingly, the IR5 ORF of EHV-1 possesses a sequence of 13 amino acids ( C AYW C CLG H AFA C ) that is a perfect match to the consensus zinc finger motif (C-X 2−4 -C-X 2−15 -CβH-X 2−4 -CβH). Putative cis -acting elements flanking the IR5 ORF include a TATA box (nucleotides 9864–9870), a CART box (nucleotides 9709–9714), and a polyadenylation signal (nucleotides 10,645–10,650). Northern blot and S1 nuclease analyses identified a single 0.9-kb mRNA species that first appears at 2 hr postinfection, and whose synthesis is reduced in the presence of phosphonoacetic acid, an inhibitor of EHV-1 DNA synthesis. Thus, the IR5 gene of EHV-1 exhibits characteristics representative of a late gene of the γ-1 class. The characterization of the IR5 gene at the DNA and RNA levels will facilitate ongoing studies to identify and characterize the IR5 polypeptide.