Tandem integration of complete and defective SV40 genomes in mouse-human somatic cell hybrids

We have analyzed the arrangement of SV40 DNA sequences integrated in human chromosome 7 in two lines of mouse-human somatic cell hybrids: one containing only one human chromosome 7 per cell and the other containing an average of about three. We found that the integration site differs in both the viral and host sequences in the two clones. However, the sites of integration into the several copies of human chromosome 7 of one clone are identical. Each chromosome 7 in both clones carries approximately six viral genomes tandemly linked. Some of these genomes lack about 20% of the DNA from the late region, including the Eco RI site.