Transcript TELOMERASE

Telomeres are repeating sequences that
allow cells to distinguish the ends of
chromosomes from broken DNA ends.
Telomerase is an RNA+protein
enzyme that solves the end
replication problem by elongating
telomeres
Normal somatic human cells do not
express telomerase, so they have a
limited lifespan
The Hayflick Limit = the number of times a cell
can divide before telomeres are critically short
Telomerase is essential in human stem
Cells in culture and in its absence cells
senesce and eventually die
One would think that a telomerase
knockout mouse would not be able
to survive…
…but this is not the case!
Telomerase knockout mice survive
for at least six generations and can
develop tumors
Telomerase is re-expressed in 90%
of human tumors
Telomerase re-expression
immortalizes cells and contributes to
cancer
Because it is present in so many
tumors, telomerase is an attractive
drug target
Targeting Telomerase could be an
issue since it is necessary for stem
cells
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