I thought shortening of telomeres was the clock of cell death, and that using telomerase to restore the shortened ends rewound the clock.
Well, it might be more involved than that, and probably is.
Telomeres reside at the end of chromosomes and shorten each time a cell divides. They are composed of repeated segments of deoxyribonucleic acid (DNA) -- the material containing the genetic code of a cell. Eventually, healthy telomeres shorten, and the cell stops dividing and enters senescence, or the state of being old.
Human cancer cells do not follow the same schedule. Some cells live too long, and some become what Shay and Wright call "immortal." Instead of shortening, the tumor cell produces an enzyme not found in normal cells -- telomerase, which maintains the length of the telomere, allowing it to divide indefinitely.
Likewise.