(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.