Telomerase activity. (A) 20- and 200-ng aliquots of
cellular extracts were assayed for the presence of telomerase activity
by the telomeric repeat amplification protocol (TRAP) assay. Extracts
(200 ng each) were heat-treated (HI) to inactivate telomerase and
assayed as a negative control. An internal PCR standard was included in
each PCR to demonstrate that an absence of telomerase did not result
from PCR inhibitors in the cell extracts. (B) Telomerase
activity measured by the TRAP assay was detected in cellular extracts
(20 and 200 ng) from HMF3 and HMME7 cells containing ectopic hTERT and
U19tsA58 LT cultured at both 33.5°C (permissive temperature for tsA58
LT) and at 39.5°C (nonpermissive temperature) for 7 days. Activity
was not detected in HMF3 and HMME7 cells containing U19tsA58 LT alone.
(C) Southern blot showing TRF lengths for the fibroblast
cultures HMF3 at p3 (lane 1), p12 (lane 2), p18 (lane 3), p24 after
early transduction of tsLT (lane 4), p23 after late transduction of
tsLT (lane 5), and p17 after both early (lane 6) and late (lane 7)
transduction of hTERT. Numerical values for mean TRF lengths of these
and other cultures are shown in Table 1.