3 Americans share Nobel medicine prize

Three Americans won the Nobel prize in medicine on Monday for discovering how chromosomes protect themselves as cells divide, work that has inspired experimental cancer therapies and may offer insights into aging.

The research by Elizabeth H. Blackburn, Carol W. Greider and Jack W. Szostak revealed the workings of chromosome features called telomeres, which play an important role in the aging of cells.

It's the first time two women have shared in a single Nobel science prize. Over the years, a total of 10 women have won the prize in medicine.

Blackburn, 60, who holds U.S. and Australian citizenship, is a professor of biology and physiology at the University of California, San Francisco. Greider, 48, is a professor in the department of molecular biology and genetics at Johns Hopkins University School of Medicine in Baltimore.London-born Szostak, 56, is a professor of genetics at Harvard Medical School and a researcher with the Howard Hughes Medical Institute.

Their work, done in the 1970s and 1980s, showed how features at the tips of chromosomes — telomeres TEE-loh-meers — can keep them from getting progressively shorter as cells divide. It's been compared to the way plastic tips on the ends of shoelaces keep the laces from fraying.Blackburn and Greider discovered an enzyme, telomerase teh-LAH-meh-race, that maintains the lengths of the telomeres. Later research has shown that telomerase is switched on in almost all cancers.

Telomerase is active before birth, when cells are dividing rapidly. By age 4 or 5 it's basically shut off in almost all cells. That means the telomeres degrade over time, leading those cells to age and eventually stop dividing. But scientists have shown that adding telomerase to human cells can extend their lifespan indefinitely. ... Such research spurred speculation that telomerase might turn out to be a fountain of youth. But experts say that aging is more complicated than just changes in telomeres.

Scientists are still studying what impact telomeres might have; perhaps they will reveal ways to ward off some aspects of aging, researchers say.