Figure 3.

EBV infection promotes lengthening of telomeres in the absence of telomerase activity. (a) Representative micrographs of Q-FISH-stained metaphase plates illustrating the heterogeneity of telomere signals in EBV-infected cells compared with mitogen-induced blasts. The chromosomes were stained by 4,6-diamidino-2-phenylindole (DAPI). (b) Quantification of the average intensity of telomere signals in EBV-infected and mitogen-induced blasts. Mean±s.e. of the number of pixels/telomere in three independent experiments. Twenty-five metaphase plates were analyzed per each time point and condition. (c) Box plots of the intensity of telomere signals in 25 randomly selected metaphase plates from EBV-infected and mitogen-induced blasts on day 21 of culture. (d) Representative SYBR gold-stained polyacrylamide gels of TRAP assay performed with cell extract from EBV-infected and mitogen-induced blasts harvested at different times after infection. The control lanes illustrate the size of the telomere template and 6-bp extension ladder obtained with the reference telomerase-positive cell extract provided by the kit. The 36-bp bands at the bottom represent the internal PCR control. The asterisk indicates a nonspecific band detected in most of the assays. (e) Mean±s.e. of total product generated (TPG) units in three independent experiments.