FREQUENCY AND DISTRIBUTION OF CHROMOSOMAL INTEGRATION SITES OF THE EPSTEIN-BARR-VIRUS GENOME

Human lymphocytes can be transformed in vitro by integration of the Ep stein-Barr virus (EBV) into the host genome. To study whether integrat ion sites are stable or changeable in the course of long-term cultivat ion, three EBV-transformed lymphoblastoid cell lines, along with posit ive control (Namalwa cell line) and negative control (noninfected lymp hocytes) cells were studied. A biotinylated Bam H1W EBV-DNA fragment w as used as the probe for fluorescence in situ hybridization to count t he numbers and to localize the sites of integrated EBV-DNA. Among thes e cell lines, the percentage of cells with integrated signals varied f rom 58% to 91%, with a mean of 1.43 to 2.66 signals per cell. No consi stent tendency of increasing or decreasing number of signals was obser ved for the three cell lines harvested at four different cultivation i ntervals (86-204 days after infection). Although the integration was n ot site-specific, high frequencies of integration did occur in all thr ee cell lines at the following chromosomal sites: 1p31, 1q31, 2q32, 3q 13, 6q24 and 7q31. Because there were multiple integration sites prese nt, it was difficult to draw any conclusion on integration site stabil ity.