Telomerase

first to put it in context

this is what's possible right now in terms of genetic manipulation:
aleph.se/../genes.html in it the guy says

"The telomeres form protective ends of the chromosomes, since normal replication tends to cut of the outermost parts of the DNA strands. At each cell division some more of the telomeres is lost, but the enzyme telomerase rebuilds these sequences.

However, apparently the telomerases gradually loose their efficiency (or are less promoted by the cell) as it ages, and the telomeres gradually shortens. When they vanish, coding genome will begin to be lost and the cell dies. This is assumed to be one major cause of cell senescence and death, the so called Hayflick-limit on cell division. "

now, since that's the background, this article has a pretty hefty implication: betterhumans.com/../articleID=2004-05-17-2

wherein it says :

"Telomerase is an enzyme that lengthens telomeres.

The researchers found that this program restores telomeres in cloned embryos regardless of the telomere length of donor cells."

so Telomerase is the fountain of youth.