Distinct regions of the human cytomegalovirus genome are responsible for the immortalization and tumorigenicity of animal cells.

Dog embryo kidney cells were efficiently transformed by human cytomegalovirus (HCMV) particles or intact viral DNA. Negative results were obtained after transfection of the canine cells with recombinant plasmids carrying the HCMV Hind III-E subgenomic fragment or with limit Bgl II and Hind III digests of the viral genome. Immortalized dog cells with typical transformation properties appeared, however, after transfection with EcoR I fragments of the HCMV DNA. Distinct regions of the viral genome are probably responsible for the immortalization and the tumorigenicity of mammalian cells.