Figure 4.

Expression of hTERT-HA does not result in telomere maintenance. (A) The TRF of a representative control, low, and high hTERT-HA-expressing clones at late passage are shown compared with the parental line at the time of transfection. The relative migration of molecular weight markers is indicated on the right. (B) Genomic DNA was isolated from hTERT-HA-expressing fibroblast clones one passage before terminal growth arrest and hybridized with a telomeric probe to visualize the TRF. Cultures of uninfected, normal (p21^+/+) cells in senescence and p21^−/− cells in crisis are included to show the telomere length at terminal growth arrest. (C) Individual telomeres (yellow) of a metaphase spread of chromosomes (blue) of a high hTERT-HA-expressing clone before crisis were identified by fluorescent in situ hybridization with a telomeric probe. Arrow denotes a chromosome end that fails to hybridize to the probe.