Tetrahymena, the one-celled organism we know as pond scum, intrigued molecular biologist Elizabeth Blackburn decades ago. Its single cell divides endlessly, seemingly immortal. Blackburn, 60, suspected that an enzyme keeps the organism's genetic material from eroding, as it does in other living things. She was right—and it works the same in humans. Now telomerase, the enzyme she codiscovered, is emerging as a key link to aging, susceptibility to certain diseases, and cancer.
Telomerase makes and replenishes telomeres, tiny units of DNA. They are protective caps like shoestring tips on the ends of chromosomes that house our genetic makeup. The length of the telomeres dictates cellular life span. As they shrink when a cell divides, so does the life of the cell. In tetrahymena, constant production of telomerase keeps the telomeres intact and the cells from dying. But the enzyme level in humans isn't high enough to confer pond-scumlike immortality, says Blackburn, a molecular and cell biologist at the University of California, San Francisco.
The ability of telomerase to renew cells has a "dark side," says Blackburn: The enzyme is perfect for fueling uncontrolled division of cancer cells. But that suggested to Blackburn that she could exploit cancer cells' already high telomerase levels and engineer mutant gene variations into the enzyme to poison the cells' telomeres. "It's a great way of killing cancer cells," she says. "They just curl up their toes and die." We're nowhere near a magic drug yet, she cautions—the approach is still too preliminary to be in human trials. But since telomerase is involved in roughly 90 percent of human cancers, she sees therapeutic potential.
What particularly fascinates Blackburn these days is the possibility of changing telomerase levels to slow the deterioration of our telomeres. A low-fat diet, regular exercise, stress reduction, and other lifestyle changes helped men with early prostate cancer boost their telomerase, she and others reported last year. She and her team previously found that chronic stress lowered telomerase and shortened telomeres in a small group of women.
It's rumored that Blackburn's research is of Nobel Prize caliber, but she refuses to speculate about that or any other form of public recognition. What she likes to mull is the implication of her findings on everyday life. That includes her own. When she is stressed, or tempted to skip a workout, sometimes she scolds herself: "Damn, my telomeres will be shortened."