Nobel prize for chromosome find

Chromosomes house genetic material

This year's Nobel prize for medicine goes to three US-based researchers who discovered how the body protects the chromosomes housing vital genetic code.

Elizabeth Blackburn, Carol Greider and Jack Szostak jointly share the award.

Their work revealed how the chromosomes can be copied and has helped further our understanding on human ageing, cancer and stem cells.

The answer lies at the ends of the chromosomes - the telomeres - and in an enzyme that forms them - telomerase.

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The 46 chromosomes contain our genome written in the code of life - DNA.

When a cell is about to divide, the DNA molecules, housed on two strands, are copied.

But scientists had been baffled by an anomaly.

For one of the two DNA strands, a problem exists in that the very end of the strand cannot be copied.

Protecting the code of life

Therefore, the chromosomes should be shortened every time a cell divides - but in fact that is not usually the case.

If the telomeres did repeatedly shorten, cells would rapidly age.

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 The Nobel Assembly

Conversely, if the telomere length is maintained, the cell would have eternal life, which could also be problematic. This happens in the case of cancer cells.

This year's prize winners solved the conundrum when they discovered how the telomere functions and found the enzyme that copies it.

Elizabeth Blackburn, of the University of California, San Francisco, and Jack Szostak, of Harvard Medical School, discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation.

Joined by Johns Hopkins University's Carol Greider, then a graduate student, Blackburn started to investigate how the teleomeres themselves were made and the pair went on to discover telomerase - the enzyme that enables DNA polymerases to copy the entire length of the chromosome without missing the very end portion.

Their research has led others to hunt for new ways to cure cancer.

It is hoped that cancer might be treated by eradicating telomerase. Several studies are under way in this area, including clinical trials evaluating vaccines directed against cells with elevated telomerase activity.

Some inherited diseases are now known to be caused by telomerase defects, including certain forms of anaemia in which there is insufficient cell divisions in the stem cells of the bone marrow.

The Nobel Assembly at Sweden's Karolinska Institute, which awarded the prize, 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."

Carol Greider, now 48, said she was phoned in the early hours with the news that she had won.

She said: "It's really very thrilling, it's something you can't expect."

Elizabeth Blackburn, now 60, shared her excitement, saying: "Prizes are always a nice thing. It doesn't change the research per se, of course, but it's lovely to have the recognition and share it with Carol Greider and Jack Szostak."

Professor Roger Reddel of the Children's Medical Research Institute in Sydney, Australia, said: "The telomerase story is an outstanding illustration of the value of basic research."

Sir Leszek Borysiewicz, chief executive of the Medical Research Council, said: "The Medical Research Council extends its congratulations to Blackburn, Greider and Szostak on winning the 2009 Nobel Prize.

"Their research on chromosomes helped lay the foundations of future work on cancer, stem cells and even human ageing, research areas that continue to be of huge importance to the scientists MRC funds and to the many people who will ultimately benefit from the discoveries they make."

美3科學家 獲諾貝爾醫學獎

2009年諾貝爾醫學獎得主傑克．索斯塔克。（路透）

2009年諾貝爾醫學獎得主伊麗莎白．布萊克本（右）和凱蘿．格蕾德（左）。（歐新社檔案照）

兩女性同獲獎 醫學獎第一次

〔編 譯魏國金／綜合斯德哥爾摩五日外電報導〕包括兩名女性在內的三名美國科學家，因發現染色體端粒（telomere）與端粒?（telomerase），進 而啟發癌症與老化過程的新研究，五日獲頒諾貝爾醫學獎殊榮。諾貝爾獎委員會也指出，這是醫學獎有史以來首次有兩名女性同時獲獎。

諾貝爾獎評審團表示，美國科學家伊麗莎白．布萊克本、凱蘿．格蕾德與傑克．索斯塔克因發現染色體如何被端粒保護，以及端粒?（酵素）在維持或去除這個重要保護罩上扮演何種角色而獲獎。評審團說：「諾貝爾獎肯定這項對細胞基礎機制的發現，該發現已激勵新醫療對策的發展。」

六十歲的布萊克本為澳洲裔，目前在加州大學舊金山分校擔任生物與生理學教授。她在凌晨二時被喚醒告知獲獎，她說：「得獎不會改變研究本身，不過能有這份肯定，並能與格蕾德、索斯塔克共享殊榮，令人高興。」

四十八歲的格蕾德則是在近清晨五點清洗衣物時被電告得獎。目前在約翰霍普金斯大學執教的格蕾德表示，該研究始於理解細胞如何運作的實驗，而非源於某種醫學應用的構想。她說：「出資贊助這類由好奇心驅使的科學，真的非常重要。」

倫敦出生的索斯塔克自一九七九年起便任職於哈佛醫學院，他說這份榮譽因與布萊克本、格蕾德共享而更為甜美，他期待有個大型歡慶派對。

發現端粒? 有助抗癌抗老化

三人將共同分享一千萬瑞典克朗（約台幣四千五百八十萬元）獎金。他們也曾因相同研究而於二○○六年獲頒有「美國諾貝爾獎」之稱的拉斯克獎。

染色體是載有遺傳物質ＤＮＡ的棒狀結構，端粒則是老化的關鍵因素，它們就像是裝置在染色體末端的保護罩。布萊克本與索斯塔克於一九八二年發現，當細胞分裂時，端粒中一個獨特的ＤＮＡ序列有保護染色體免於降解之效。

在 格蕾德協助下，布萊克本也辨識出能製造端粒ＤＮＡ的端粒?，倘若端粒耗損，細胞就會變老。然而，如果端粒?的濃度高，端粒長度得以維持，細胞的老化便可獲 得抑制。同時，端粒?濃度過高將使細胞無止境地複製，進而可能引發癌症。研究發現，端粒?在許多癌細胞上非常活躍，透過端粒?抑制劑找到阻斷該機制的方 式，因而成為癌症研究中最熱切探索的領域。