An adult human comprises roughly 100 000 billion cells all originating through division from a single fertilised egg cell. To do this the cell swells, duplicating its chromosomes to split into two equal cells. The 2001 award in physiology or medicine was divided evenly between Tim Hunt and Paul Nurse, both of the Imperial Cancer Research Fund (ICRF), UK, for their individual discoveries concerning molecules that regulate the cell cycle, and American Leland Hartwell for his discoveries of a specific class of genes that control the cell cycle. This may open new possibilities for cancer treatment, as defects in cell cycle control may lead to the type of chromosome alterations seen in cancer cells. In the early 1980s Hunt discoved the first cyclin molecules, so named because the levels of these proteins vary during the cell cycle. The cyclins bind to the CDK (cyclin dependent kinase) molecules, regulating the CDK activity and selecting the proteins to be phosphorylated. He showed that cyclins are degraded at each cell division, an important mechanism for cell cycle control.
Tim Hunt was born in 1943 at Neston in the Wirral, near Liverpool, but grew up in Oxford, where his father worked at the Bodleian Library. His education began oddly with latin lessons from a governess, and the infants department of the Oxford High School for Girls before moving to the Dragon School, where he first became fascinated by biology. At 14, he entered Magdalen College School, where his interest in science grew – he even dissected his brother’s pet rabbit when it died – and attended regular lectures in the city. In 1961 Hunt entered Clare College, Cambridge, to read natural sciences. He joined the department of biochemistry in 1964, working on the control of translation of mRNA. In 1966, he visited Irving London at the Albert Einstein College of Medicine in New York for further studies, and joined him full time after gaining his PhD in 1968.
Hunt returned to Cambridge and continued to work on RNA throughout the 1970s, and began teaching summer
courses at the Marine Biological Laboratory, Woods Hole, Massachusetts, to look at changes in protein synthesis in sea urchin and clam eggs after fertilisation. In 1979, he helped Joan Ruderman and Eric Rosenthal with experiments on the translational control of maternal mRNA; the major mRNAs concerned later turned out to be the A and B-type cyclins. By 1982, Hunt felt he had exhausted the potential of sea urchin eggs, but it was then that he performed a simple protein experiment that led to the discovery of cyclins and their degradation. In 1990, Hunt joined ICRF, (now Cancer Research UK) in London. He became a fellow of the Royal Society in 1991 and a foreign associate of the US National Academy of Sciences in 1999. He was knighted in 2006.
This text and the picture of the Nobel Laureate were taken from the book: "NOBELS. Nobel Laureates photographed by Peter Badge" (WILEY-VCH, 2008).
By Volker Steger
This is not just a Nobel Laureate, but a knight, too. Sir Tim is a very nice,
likeable gentleman. He just loves this photo project, posing, and even
jumping with his drawing! Later he does the unexpected: he photographs
me using a small camera he pulls out of his coat pocket. The next day, I
receive his pictures in my mail, signed, “Best regards, Tim. This is the bait,
now send me my pictures!” He got them quickly after that! Looking back Iʼm
amazed how scientific and precise his drawing turned out to be.
Er ist nicht nur einfach ein Nobelpreisträger, sondern sogar ein geadelter
Nobelpreisträger. Sir Tim ist wirklich nett, ein sympathischer Gentleman. Er
genießt dieses Fotoprojekt einfach und posiert, ja springt sogar mit seiner
Zeichnung durch die Luft! Später tut er das Unerwartete: Er fotografiert mich
mit einer kleinen Kamera, die er aus seiner Manteltasche zieht. Am nächsten
Tag erhalte ich seine Bilder per Post, signiert mit „Freundliche Grüße, Tim.
Dies ist der Köder, damit Sie mir sofort meine Bilder senden!“ Er hat sie sehr
schnell bekommen! Im Rückblick bin ich erstaunt, wie wissenschaftlich
und präzise seine Zeichnung geraten ist.
Subdividing Cell Division
by Adam Smith
“Aha, the cell cycle!”, exclaims Tim Hunt. “What is the cell cycle? Well I like a sort of simple definition, which is that the cell cycle is a series of events, or you might call them processes, which cells in our bodies have to go through in order to reproduce themselves.”
The cell cycle is conventionally divided into four phases, of which the important ones have been placed by Hunt at the top and bottom. Mitosis, at the top, is the process when the cell actually divides into two and S-phase (which stands for ‘DNA Synthesis phase’), at the bottom, is when the chromosomes are replicated. And in between those two important events are G1 and G2, standing simply for ‘Gap 1’ and ‘Gap 2’.
The checkpoints, a concept introduced by Hunt’s co-Laureate Leland Hartwell, are places in the cell cycle where the cell decides whether or not to go on. So, for example, the first checkpoint on the top left side of the diagram is where the cell checks to make sure that the chromosomes have been fully replicated and that they don’t have any damage, before going into mitosis.
As for the cyclins, the proteins which Hunt discovered, he remarks that “it’s sort of hard to explain that you won an important scientific prize for discovering something that went away.” But that’s how they were discovered. Hunt analysed the proteins made by sea urchin eggs after they were fertilised, up to and including the time when they first divided. Taking out samples every ten minutes, he noticed that one of the proteins suddenly faded away when the cells divided. “That struck me as very extraordinary,” he recalls.
The cyclins he uncovered turned out to be key regulators of the cell cycle that combine with another regulator protein discovered by Hunt’s other co-Laureate, Paul Nurse, called CDK1 (cyclin-dependent kinase 1). That word “dependent” means that without the cyclins this kinase won’t work, so when the cyclins are degraded, the kinase turns off.
“I mean it’s interesting that you’d think that something as fundamental as cell division would all have been figured out long ago,” says Hunt, “but actually there’s still an awful lot to work out. Each of those arrows is an adventure, and that’s the amazing thing, how long it takes to figure stuff