cells counting off in culture

Michael J Conboy conboymj at leland.Stanford.EDU
Mon Jan 16 17:49:37 EST 1995

	It is my understanding that the cellular clock in somatic cells
is telomere length.  In the absence of telomerase, telomeres progressively
shorten with each cell division.  Dividing cells from an older person
have shorter telomeres and less potential doublings than dividing cells
from a young person.  Germ cells, immortal cell lines and tumor cells
have active telomerase, and longer, stable telomeres.  I'm not sure
anyone knows exactly how the telomere length regulates the ability of
the cell to divide, but short telomeres have less heterochromatin,
more transcriptional activity, and a higher incidence of recombination.
Thus a short telomere may cause the expression of a nearby senescence
regulator gene, or cause gross chromosomal mutation.
	Look in the December twenty-something, 1994 issue of Science
(telomerase activity and immortal cells) and the October 21 issue (a
great paper on the cloning of a yeast telomerase component).



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