Molecular cloning and mapping of rat cytomegalovirus DNA

The DNA of a rat cytomegalovirus (RCMV) isolate from England is cleaved by HindIII into 25 fragments, 20 of which have been cloned into recombinant plasmids. Twenty-two of thirty KpnI fragments were similarly cloned which, together with the HindIII clones, resulted in cloning of 93% of the viral genome. Terminal fragments were identified and restriction site maps were constructed of the viral genome for HindIII, KpnI, and HpaI. The lack of cross-hybridization among fragments derived with each restriction enzyme and the finding of only two termini support the view that RCMV DNA consists of one long unique sequence. The size of the genome of the English strain of RCMV is approximately 206 kbp, much smaller than that of the previously reported “Dutch” strain.