Localization polymorphism of EBV DNA genomes in the chromosomes of Burkitt lymphoma cell lines

The localization of Epstein-Barr virus (EBV) genomes in nuclei of the human lymphoblastoid cell lines Raji, Jijoye, P3HR-1, Daudi and Ramos was investigated by in situ hybridization with biotinylated EBV DNA probes. We found that all sites of hybridization were associated with the chromosomes. Only some of these sites were present on both chromatids and these had a non-random distribution; these sites could represent EBV sequences integrated at specific points on the chromosomes. The total mean site number corresponded with the number of viral DNA copies estimated in the different cell lines by other techniques, but the copy number was highly variable from cell to cell in a given line.