Structure of the genome of equine herpesvirus type 3

Abstract

Restriction endonuclease mapping studies were performed to determine the molecular structure of the genome of equine herpesvirus type 3 (EHV-3). Purified EHV-3 DNA, either unlabeled or 32P-labeled, was analyzed using the restriction enzymes BamHI, BclI, BglII, EcoRI, and HindIII. The findings that four 0.5 M (molar) fragments were present, that two of these were terminal fragments, and that all 0.5 M fragments contained homologous DNA sequences as judged by DNA hybridization analyses indicated that DNA sequences located at one terminus are repeated within the molecule and that two populations of molecules exist with regard to the arrangement of this pair of shared sequences. Mapping of BamHI, BclII, BglII, EcoRI, and HindIII fragments by double digestion of intact EHV-3 DNA, reciprocal digestion of isolated restriction enzyme fragments, and blot hybridization experiments revealed that the EHV-3 genome is a linear, double-stranded DNA molecule with a molecular size of 96.2 ± 0.48 MDa and is comprised of two covalently linked segments, designated L (long) and S (short). The S region is approximately 22.9 MDa in size and consists of a unique segment (U s) of approximately 5.8 MDa bracketed by 8.5 MDa inverted repeat sequences that allow the S region to invert relative to the fixed L region which is approximately 73.3 MDa in size and consists only of unique sequences. Thus, these data confirm that EHV-3 DNA exists in two isomeric forms and has a molecular structure similar to that of the genomes of EHV-1 ( B. E. Henry, S. A. Robinson, S. A. Dauenhauer, S. S. Atherton, G. S. Hayward, and D. J. O'Callaghan, 1981; D. J. O'Callaghan, G. A. Gentry, and C. C. Randall, 1983; D. J. O'Callaghan, B. E. Henry, J. H. Wharton, S. A. Dauenhauer, R. B. Vance, J. Staczek, and R. A. Robinson, 1981; W. T. Ruyechan, S. A. Dauenhauer, and D. J. O'Callaghan, 1982), pseudorabies virus ( W. Stevely, 1977; T. Ben-Porat, F. J. Rixon, and M. L. Blankenship, 1979), varicella-zoster virus ( A. M. Dumas, J. L. Geelen, M. W. Weststrate, P. Wertheim, and J. Van Der Noordaa, 1981; S. E. Straus, H. S. Aulakh, W. T. Ruyechan, J. Hay, T. A. Casey, G. F. Vande Woude, J. Owens, and H. A. Smith, 1981; S. E. Straus, J. Owens, W. T. Ruyechan, H. E. Takiff, T. A. Casey, G. F. Vande Woude, and J. Hay, 1982) and bovine herpesvirus type 1( J. E. Mayfield, P. J. Good, H. J. Van Oort, A. R. Campbell, and D. E. Reed, 1983).