Electron microscopic study of equine herpesvirus type 1 DNA.

Electron microscopic studies of equine herpesvirus DNA revealed that single strands that were allowed to reanneal formed single-stranded loops with double-stranded stems only at one end of the molecule. These observations support restriction enzyme analyses which indicate that the 92-megadalton DNA molecule exists as a long region of unique sequences covalently linked to a short region. The short region is comprised of an internal unique sequence, which forms the loop during reannealing of single strands, and two terminal inverted repeat sequences that bracket the unique sequence and form the double-stranded stem structure observed upon reannealing of single strands. Measurements of the unique sequence and terminal inverted repeat subgenomic sequences indicate a size of 6.4 megadaltons for each and thus fix the size of the short region at approximately 19.2 megadaltons.