Demonstration of the Colinearity of Human Cytomegalovirus Genomes and Construction of Restriction Maps of Unknown Isolates Using Cloned Subgenomic Fragments

In this study, we have established the colinearity of human cytomegalovirus (HCMV) genomes using stringent conditions of DNA-DNA filter hybridization of HCMV HindIII fragments and cosmid-cloned AD169 strain HCMV DNA fragments. Large cosmid-cloned fragments of AD169 DNA were used for the preparation of radioactive probes by nick translation. These probes were hybridized to HindIII digests of DNA from three fresh isolates of HCMV and to that of the Davis strain. Using published HindIII restriction maps for the AD169 strain as a reference, the results obtained by hybridization allowed us to construct HindIII restriction maps for the genomes of the three fresh isolates. Confirmation of our methodology was found in the correspondence between the HindIII map we constructed for the Davis strain and that published previously. Furthermore, it is shown that variation in the restriction profiles of the unique regions of the genome are due to the absence or gain of restriction sites, and not to a rearrangement of fragments. This technique allows rapid construction of physical maps of the DNA of any fresh isolate for a given restriction enzyme provided the corresponding restriction map of a strain to be used as reference is available.