2009诺贝尔生理学或医学奖揭晓 美国科学家获奖

卡萝尔・格雷德的资料照片。新华社/法新

伊丽莎白・布莱克本的资料照片。新华社/法新

杰克・绍斯塔克的资料照片。新华社/法新

　　卡罗林斯卡医学院发布的新闻公报说，这三位科学家的发现“解决了一个生物学的重要课题，即染色体在细胞分裂的过程中是怎样实现完全复制的，同时还能受到保护不至于发生降解。”

　　伊丽莎白・布莱克本和卡萝尔・格雷德都是女性科学家，两人分别出生于1948年和1961年。她们将与现年57岁的杰克・绍斯塔克分享1000万瑞典克朗(约合140万美元)的奖金。

Three Americans Win Physiology or Medicine Nobel

By Gretchen Vogel
ScienceNOW Daily News
5 October 2009

Telomeres are repetitive stretches of DNA that cap the ends of chromosomes. First described in the 1950s, telomeres were initially thought to prevent chromosomes from attaching to each other. In 1982, Blackburn and Szostak showed that the telomere sequence from a single-celled organism called a tetrahymena could prevent the usual degradation of foreign DNA that was inserted into yeast, suggesting that telomeres work to protect DNA. It has later became clear that telomeres also help their own cell's DNA: DNA-copying enzymes can't read all the way to the end of the chromosome, inevitably producing a slightly shorter copy than the original; without telomeres, important stretches of DNA would be lost every time a cell divides.

Two years later, while Greider was a graduate student in Blackburn's lab, she discovered the enzyme telomerase, which adds telomere sequences to the ends of chromosomes, keeping them "topped up" and long enough to make up for the shortening during cell division. The pair isolated and characterized the enzyme, which is part protein and part RNA. (The RNA provides a template for the telomere DNA sequence.)

Work from Szostak's lab and Blackburn's lab showed that without telomerase, cells will eventually stop dividing and will die. Some people initially guessed that telomerase might be a fountain of youth, preventing aging in both cells and entire organisms. But the story isn't that simple. Many types of cancer cells, it turns out, have overactive telomerase that allows them to continue dividing when they shouldn't. There are clinical trials under way testing whether a vaccine against telomerase could help fight certain kinds of cancer.

Not having enough telomerase is bad news as well, though. A rare disorder called dyskeratosis congenita, which causes symptoms that resemble premature aging, is caused by a faulty telomere-maintenance system. That discovery hasn't yet led to a treatment for the disease, says Tom Vulliamy of the University of London, who studies the disorder. "Sometimes we're a bit impatient in how quickly our discoveries impact in health care. ... I am sure that the understanding of telomeres will help us treat patients someday."

This year's prize is the first Nobel to be shared by two women. Blackburn and Greider are just the ninth and 10th women, respectively, to be awarded the prize in physiology or medicine in the award's 108-year history.

For full coverage of this prize, see the 9 October issue of Science.