The Nobel Prize was awarded today to three American scientists for their discoveries related to how chromosomes protect themselves from degradation. The discovery has huge significance in the areas of cancer research and aging. It was also the first Nobel awarded to more than one woman.
Sharing the $1.4 million prize are Elizabeth Blackburn of the University of California, San Francisco, Carol Greider, Ph.D. of Johns Hopkins University School of Medicine and Jack Szostak, Ph.D. of Massachusetts General Hospital.
The New York Times reported that although the award was swept by Americans again, two of the three were immigrants. The Times also explained the science behind the award:
The recipients solved a longstanding puzzle involving the ends of chromosomes, the giant molecules of DNA that embody the genetic information. These ends, called telomeres, get shorter each time a cell divides and so serve as a kind of clock that counts off the cell’s allotted span of life.
The field of telomere research grew out of a puzzle in the mechanics of copying DNA. The copying enzyme works in such a way that one of the two strands of the double helix is left a little shorter after each division. Work by the three winners and others led to the discovery of telomerase, a special enzyme that can prevent the shortening by adding extra pieces of DNA.
Dr. Blackburn addressed this problem by working with a single-celled organism found in pond water known as Tetrahymena. It was particularly suitable because its genome is divided into many small chromosomes so each cell has a large number of telomeres.
While she and Dr. Greider were working with Tetrahymena, Dr. Szostak was studying the same problem in yeast. The two groups in collaboration worked out the basic mechanism of how telomerase works and the special piece of RNA it carries to help elongate the chromosomes. RNA is a close chemical cousin of DNA.
This piece of basic biology soon turned out to have important implications for aging and cancer. Telomerase is usually active only at the beginning of life; thereafter the telomeres get shorter each time a cell divides. When they get too short, a cell is thrown into senescence, meaning that it is prevented from dividing again.
Short telomeres are known to play a role in certain diseases of aging, and may be of more general importance. Telomeres are also important in cancer, a disease in which control of cell proliferation is lost. Cancer cells need to reactivate the telomerase gene, or their telomeres will get steadily shorter, forcing them into senescence. In some 80 to 90 percent of human cancer cells, the telomerase gene has been switched back on, Dr. Blackburn said. Clinical trials are under way to see if cancers can be treated by inhibiting telomerase.
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