The 2009 Nobel Prize in Physiology or Medicine will go to three Americans who discovered telomeres, the genetic code that protects the ends of chromosomes, and telomerase, the enzyme that assists in this process, findings that are important in the study of cancer, aging and stem cells.

Announced this morning in Stockholm, the three geneticists—Elizabeth Blackburn, a professor of biology and physiology at the University of California, San Francisco, Carol Greider, a professor in the department of molecular biology and genetics at Johns Hopkins University School of Medicine in Baltimore, and Jack Szostak, a professor of genetics at Massachusetts General Hospital in Boston, who are all previous Scientific American authors—will split the award of 10 million Swedish kronor (about $1.4 million), along with the prestige and honor.

The work for which they received the award illuminated key aspects of the DNA replication process. As genetic material is copied from the chromosome during cell division, the whole DNA strand must be duplicated from end to end, otherwise, portions of genetic information will be lost. Until the 1980s, it was a mystery as to how the chromosomes could be reliably copied the whole way through without missing bits and pieces at the very end of each strand. Work completed by this year’s laureates demonstrated how, if parts of the end-cap telomeres were missing, DNA would eventually be shortened and cut off in the replication process.

Blackburn and Szostak, who had been studying the ends of chromosomes and minichromosomes respectively, met at a conference in 1980, after which they began collaborating. Two years later, they demonstrated in a paper published in Cell that the telomere sequence could be isolated, inserted into another organism and still serve the same function. Working with Blackburn, Greider helped in 1989 to identify the RNA-based telomerase—the enzyme that creates the crucial telomeres—in a paper published in Nature. (Scientific American is part of the Nature Publishing Group.)

The findings have since been applied in studies of aging, stem cells and cancer. Early research by Blackburn and Szostak showed that if telomeres were shortened it would lead to slower cell division and premature aging in yeast—and later in human cells. Since the early discoveries, defective telomeres have also been found to play a role in some forms of inherited anemia, as they affect the division of bone marrow stem cells. Cancer may also be in part a disease of telomere dysfunction. Given the rapid rate of division among cancer cells, they have been a more recent target of telomere research. Treatments taking advantage of this new knowledge are in clinical trails—the data from which are still outstanding—noted the Nobel Committee. 

Although findings related to this research have been generating much excitement in the field of cancer research—as well as that of aging—those issuing the award note that much study remains to be done.  "Now it will be very important to figure out what is real, what is mechanism and what is statistical noise," said Goran Hansson, a professor of cardiology at the Karolinska Institute and member of the Prize Committee, said during the announcement press briefing.

For the researchers, much of the early discoveries were driven by general curiosity about the workings of chromosomes and DNA replication. "We had no idea when we started this work that telomerase would be involved in cancer, but were simply curious about how chromosomes stayed intact," Greider said in a statement after winning the Lasker Award in 2006 for some of the same research. "Our approach shows that while you can do research that tries to answer specific questions about a disease, you can also just follow your nose."

Jeremy Berg, director of the National Institute of General Medical Sciences was pleased to see an example of general research chosen for the prize. He calls it "A great example of a curiosity-driven process." The selection of telomeres research was not a surprise to many in the field, he says, as the research has "been moving along steadily under its own power…[and] everybody had known how important it was. "Nevertheless, there are some large questions that remain to be answered about the workings of telomeres and the associated telomerase—in addition to results from the ongoing clinical trials. From an evolutionary standpoint, for example, the similarities between telomerase and the reverse transcriptase in retroviruses and living telomereless knockout mice beg for further study, Berg notes.

This is the first time in the prize's 108-year history that more than one woman has been awarded the prize in medicine in a single year. Only eight other women have won the medical Nobel. Last year's Nobel Prize in Physiology or Medicine was shared by Harald zur Hausen—for his work discovering the link between the HPV (the human papilloma virus) and cervical cancer—and Francoise Barre Sinoussi and Luc Montagnier—for their joint discovery of HIV (the human immunodeficiency virus).