杏吧原创

TWO Britons and an American have won science鈥檚 top prize for discovering how
living cells grow, divide and multiply.

Paul Nurse and Tim Hunt of the London-based Imperial Cancer Research Fund
have become the first Britons since 1988 to win the Nobel Prize in Physiology or
Medicine. They share the prize with Leland Hartwell, director of the Fred
Hutchinson Cancer Research Center in Seattle.

Each of the winners discovered key genes and proteins that orchestrate the
growth and division of cells鈥攖he cell cycle. This is such a fundamental
process in all plants and animals that their work is important in every field of
biology, especially medicine.

Through work on mutant strains of baker鈥檚 yeast, Hartwell discovered a
hundred or so 鈥渃ell-division cycle鈥� genes. One, called CDC28, triggers
the whole process. It was also Hartwell who realised that there are
鈥渃heckpoints鈥� or delays in the cell cycle while damaged DNA is repaired. These
are important because they prevent cells with damaged DNA from dividing. If the
checkpoints go awry, cells can divide out of control and become cancerous.

By studying mutants of another yeast, Nurse discovered cdc2, a
master gene controlling many phases of the cell-division cycle. Next, Nurse
proved that we humans also have our own version of cdc2, which codes
for a protein called CDK1. 鈥淚t was a real eureka moment,鈥� says Nurse. 鈥淚t meant
that the same gene controls everything in organisms from yeast to humans.鈥�

Hunt, working on eggs from the sea urchin Arbacia, discovered that
CDK1 is activated by proteins called cyclins. He found that levels of cyclin
increase greatly in cells as they approach division, then 鈥渧anish into thin air鈥�
once division is complete. 鈥淚 knew I鈥檇 made a very important discovery straight
away,鈥� Hunt says.