>P.N.A.S. Vol. 96, Issue 7, 3723-3728, March 30, 1999
>> Cell Biology
> Telomerase extends the lifespan of virus-transformed human
> cells without net telomere lengthening
>> Jiyue Zhu*,, He Wang*,, J. Michael Bishop,, and Elizabeth H. Blackburn,§
>> The G. W. Hooper Foundation, Department of Microbiology and Immunology, University of California,
> San Francisco, CA 94143
>> Contributed by Elizabeth H. Blackburn, January 14, 1999
>> Human fibroblasts whose lifespan in culture has been extended by expression of a viral oncogene eventually undergo a growth crisis marked by failure
> to proliferate. It has been proposed that telomere shortening in these cells is the property that limits their proliferation. Here we report that ectopic
> expression of the wild-type reverse transcriptase protein (hTERT) of human telomerase averts crisis, at the same time reducing the frequency of dicentric
> and abnormal chromosomes. Surprisingly, as the resulting immortalized cells containing active telomerase continue to proliferate, their telomeres
> continue to shorten to mean lengths below those in control cells that enter crisis. These results provide evidence for a protective function of human
> telomerase that allows cell proliferation without requiring net lengthening of telomeres.
>
