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Mechanism of yeast telomerase enzyme revealed
By Birgit Hofmann

Scientists have been intensively studying telomerase activity in cells to find out more about the enzyme's role in both aging and cancer. Recent findings by a research team led by microbiologist Elizabeth H. Blackburn, of the University of California, San Francisco, suggest that a region of the telomerase molecule could prove to be a target for killing cancer cells or regenerating dying cells. It might also lead to a possible target for HIV therapy. The research results are published in the May 5 issue of Science.

Telomerase is an enzyme—found in the cells of human beings and simple organisms alike—that patrols the end portions of chromosomes, called telomeres. Telomeres not only hold the two ends of chromosomes together and prevent them from unwinding; they also play a role in the aging process of a cell because they lose their final fragments whenever a cell divides. As the telomeres gradually become very small, the cell stops dividing and eventually dies.

The telomerase enzyme—active in cells that are rapidly dividing, as in the self-renewal of adult cells of the immune system or in cancer—has the ability to prevent the shortening of the telomeres by adding DNA back onto the chromosome ends. The researchers have now discovered a small region within the RNA molecule of yeast telomerase that is responsible for this function.

"This discovery represents the first time anybody has shown a mechanistic role for a structure of RNA in the action of telomerase, and we think this is probably a universal kind of feature of telomerase," says Blackburn in a statement for the press.

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Tzfati, Y., Fulton, T.B., Roy, J., & Blackburn, E.H. Template boundary in a yeast telomerase specified by RNA structure. Science 288, 863-867 (May 5, 2000).

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