STOCKHOLM (Reuters) - Three Americans won the Nobel prize for medicine on Monday for discovering and identifying telomerase, the enzyme that renews the little caps on the end of chromosomes whose natural fraying underlies aging and cancer.

Australian-born Elizabeth Blackburn, British-born Jack Szostak and Carol Greider won the prize of 10 million Swedish crowns ($1.42 million), Sweden's Karolinska Institute said.

"The discoveries...have added a new dimension to our understanding of the cell, shed light on disease mechanisms, and stimulated the development of potential new therapies," it said.

Blackburn, Greider and Szostak's work laid the foundation for studies that have linked telomerase and telomeres to human cancer and age-related conditions.

Work on the enzyme has become a hot area of drug research, particularly in cancer, as it is thought to play a role in allowing tumor cells to reproduce out of control.

Merck & Co, for example, is developing a vaccine that targets telomerase under an agreement with U.S. biotech company Geron, with early trials of its so-called therapeutic vaccine under way since last year.

"This has broad medical implications for cancer, certain inherited diseases and for aging," said Rune Toftgard, a professor at Karolinska Institutet.

"FOLLOW YOUR NOSE"

Carol Greier, 48, who grew up in Davis, California, where her father was a physicist, said the Nobel prize recognized the value of discoveries driven by pure curiosity.

"We had no idea when we started this work that telomerase would be involved in cancer, but were simply curious about how chromosomes stayed intact," she said in an emailed statement.

"Our approach shows that while you can do research that tries to answer specific questions about a disease, you can also just follow your nose," she said.

Greider started research on telomerase in the late 1970s with Blackburn, her academic adviser, who pioneered research into chromosomes and DNA at the University of California.

An outspoken researcher, Blackburn was fired in 2004 from then-President George W. Bush's Council on Bioethics for her criticism of his policy on embryonic stem cell research.

Blackburn, who was born in 1948 to a family of scientists, and her two fellow Nobel recipients, were among those considered likely winners in a Thomson Reuters forecast.

Dr. Jeremy Berg of the U.S. National Institute of General Medical Sciences, which funded some of the research, said this year's prize was no surprise.

"It was at the top of all lists this year," Berg said in a telephone interview. "The work on telomeres and telomerase is a classic in curiosity-driven discovery in a fundamental biological process."

Telomeres had been discovered decades before but Blackburn wondered how they got copied, in essence, renewing the cell's life.

"People started making connections right away with cancer and cellular aging," Berg said.

Berg says Szostak, 56, has moved along since his work on telomerase.

"He is trying to figure out how he can make proto-cells and get them to copy their genetic material. That's almost literally creating life in a test tube."

Blackburn is with the University of California, San Francisco, Greider is with the Johns Hopkins School of Medicine in Baltimore. Szostak, at Harvard Medical School since 1979, is currently at the Massachusetts General Hospital in Boston and the Howard Hughes Medical Institute.

Medicine is traditionally the first of the Nobel prizes awarded each year. The prizes for achievement in science, literature and peace were first awarded in 1901 accordance with the will of dynamite inventor and businessman Alfred Nobel.

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