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Francois Jacob

(1920 - 2013)

Francois Jacob was a Jewish French biologist who was the recipient of the 1965 Nobel Prize in Medicine.

Jacon (born June 17, 1920; died April 19, 2013) was born in Nancy, France. Following his studies at the Lycee Carnot in Paris, Jacob began studying medicine at the Faculty of Paris. During World War II, Jacob joined the Free French Forces in London. He was sent as a medical officer to several locations in Africa and Europe. Jacob was wounded in both Tunisia and in Normandy (August 1944). On account of the injuries, Jacob was unable to practice medicine.

In 1950, Jacob joined the research team at the Institut Pasteur under the guidance of André Lwoff. In 1951, he obtained a science degree, and then a doctorate in science in 1954 at Sorbonne. After graduation, in 1956, he was appointed Laboratory Director at the Institut Pasteur. Then in 1960, he became the Head of the Department of Cell Genetics at the Institut. In 1964, he accepted a faculty position at the Collège de France.

In 1965, Jacob received the Nobel Prize for Medicine, along with Jacques Monod and André Lwoff, for their research on the idea that control of enzyme levels in all cells happens through feedback on transcription. He is also a member of the Royal Society in London (1973) and Academy of Sciences of the United States (1969).

Nobel Prize Research

Around 1961, Jacob and Jacques Monod explored the idea that the control of enzyme expression levels in cells is a result of feedback on the transcription of DNA sequences. Their experiments and ideas gave impetus to the emerging field of molecular developmental biology, and of transcriptional regulation in particular.

For many years it had been known that bacterial and other cells could respond to external conditions by regulating levels of their key metabolic enzymes, and/or the activity of these enzymes. For instance if a bacterium finds itself in a broth containing lactose, rather than the simpler sugar glucose, it has to adapt itself to the need to 1) import lactose, 2) cleave lactose to its constituents glucose and galactose, and 3) convert the galactose to glucose. It was known that cells ramp up their production of the enzymes that do these steps when exposed to lactose, rather than wastefully producing these enzymes all the time. Studies of enzyme activity control were progressing through theories of the (allosteric) action of small molecules on the enzyme molecule itself (switching it on or off), but how the production of enzymes themselves were controlled was less easy to understand.

With the earlier determination of the structure and central importance of DNA, it became clear that all proteins were being produced in some way from its genetic code, and that this step might form a key control point. Jacob and Monod made key experimental and theoretical discoveries that demonstrated that in the case of the lactose system outlined above (in the bacterium E. coli), there are specific proteins that are devoted to repressing the transcription of the DNA to its product (RNA, which in turn is decoded into protein).

This repressor (the lac repressor) is made in all cells, binds directly to DNA at the genes it controls, and physically prevents the transcription apparatus from gaining access to the DNA. In the presence of lactose, this repressor binds lactose, making it no longer able to bind to DNA, and the transcriptional repression is lifted. In this way, a robust feedback loop is constructed that allows the set of lactose-digesting proteins products to be made only when they are needed.

Sources: Wikipedia; Nobel Prize