Anatomy of Bovine Mammillitis DNA I. Restriction Endonuclease Maps of Four Populations of Molecules That Differ in the Relative Orientation of Their Long and Short Components

Abstract

The DNA of bovine mammillitis virus (BMV) consists of 2 covalently linked components that are 71.5 .times. 106 and 15.7 .times. 106 in MW and is designated as L and S, respectively. The BMV DNA consists of 4 equimolar populations differing only in the orientation of the L and S components relative to each other. The sum MW of fragments generated by digestion of BMV DNA with Hsu I, Hpa I, Bgl II or Xba I significantly exceeds the established MW of the intact DNA. In each digest, the fragments form 3 groups differing in molar concentration. In reference to the molar concentration of intact DNA, each enzyme digest contained a set of four fragments 0.25 M in concentration, a set of 4 fragments 0.5 M in concentration, and a variable size set, unique for each enzyme digest, 1.0 M in concentration. Experiments involving digestion of intact DNA by [phage] .lambda. exonuclease followed by restriction endonuclease digestion established that each of four 0.5 M fragments were positioned at the termini of the BMV DNA. Complete maps for the fragments generated by each enzyme established that the 0.25 M fragments arise by fusion of the sequences of the terminal fragments when these are juxtaposed as a consequence of the inversion of L and S components. The maps also established the dimensions of the L and S components. The structure of BMV DNA is apparently similar to that of HSV [herpes simplex virus] DNA previously shown to consist of 2 unequal size components that invert relative to each other.