U.S. scientists win Nobel Prize-medicine

STOCKHOLM, Sweden, Oct. 5 (UPI) -- Three U.S. scientists earned the 2009 Nobel Prize in Physiology and Medicine for work on how chromosomes are protected, the Nobel Foundation in Sweden said.

Elizabeth H. Blackburn, Carol W. Greider and Jack W. Szostak addressed a major problem in biology of how the chromosomes could be copied in a complete way during cell divisions and how they are protected against degradation, the foundation said in a news release.

The laureates showed the answer lies in the telomeres and telomerase -- the ends of the chromosomes and the enzyme that forms them, the foundation said.

DNA molecules carry human genes in chromosomes capped by telomeres on their ends. Blackburn and Szostak discovered that a specific DNA sequence in the telomeres protects the chromosomes from degradation. Greider and Blackburn identified telomerase, the enzyme making telomere DNA. The body of work explain how the ends of the chromosomes are protected by the telomeres and that they are built by telomerase.

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

Blackburn has dual U.S-Australian citizenship. Since 1990, she has been professor of biology and physiology at the University of California in San Francisco.

Greider was appointed professor in the department of molecular biology and genetics at Johns Hopkins University School of Medicine in Baltimore in 1997.

Szostak is professor of genetics at Massachusetts General Hospital in Boston and affiliated with the Howard Hughes Medical Institute.