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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
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
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
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Lacking Telomerase RNA.” Cell. Vol 91 No 1. 3 October 1997 25-34
De Lange, Titia. “Shelterin: the protein complex that shapes and safeguards human telomeres.” Genes and
Development. 2005 vol 19 2100-2110
Greider, Carol W. “Telomerase Discovery: The Excitement of Putting Together Pieces of the Puzzle (Nobel
Lecture). Angewandte Chemie International Edition. Vol 49 issue 41 p.7422-7439 4 October 2010.
Hamilton, Jon. “Matching DNA with Medical Records to prevent Disease and Aging.” NPR. 19 November
2012. <>
Hiyama, E and K. Hiyama. “Telomere and Telomerase in Stem Cells.” British Journal of Cancer. Vol 96 No.
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Mathon, Nicole F. and Alison C. Lloyd “Box 1: Telomeres and telomerase” from “Milestones in Cell Division:
Cell Senescence and Cancer.” Nature
Mocellin, Simone, Karen A. Pooley, and Donato Nitti. “Telomerase and the search for the end of cancer.”
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Shay, Jerry W., Ying Zou, Eiso Hiyama, and Woodring E. Wright. “Telomerase and Cancer” Human
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“Telomere Functioning.” Pharminox. <>