GENE ORGANIZATION IN THE U-L REGION AND INVERTED REPEATS OF THE CANINE HERPESVIRUS GENOME

Restriction mapping and the determination of scattered nucleotide sequ ences have permitted a description of the global structure and evoluti onary affinities of the canine herpesvirus (CHV) genome. The global st ructure closely resembles that of the totally sequenced genomes of var icella-zoster virus and equine herpesvirus 1 (EHV-1) in having a 37 bp inverted repeat flanking a long unique region (U-L) of approximately 100 000 bp, and a 10 100-10 700 bp inverted repeat flanking a short un ique region (U-S) of roughly 7400-8600 bp. On the basis of the sequenc es obtained, 35 homologues to previously identified herpesvirus gene p roducts were found in U-L and the major inverted repeat, and the level of the similarities indicated that CHV belongs to the genus Varicello virus. Within the genus, CHV appears to be most closely related to EHV -1, pseudorabies virus and feline herpesvirus. Surprisingly, genes for both subunits of the viral ribonucleotide reductase were found to be missing from their equivalent place in other herpesvirus genomes. Eith er they have been translocated to another position in the CHV genome o r, we think more likely, they have been lost.