Researchers hope the discovery will help find new drugs for jet lag and mental health treatments.
The body clock keeps us in tune with the pattern of day and
night. It means we sleep at night, but also affects hunger, mood and
Light acts like a reset button to keep the clock to time, but
when we fly around the world it takes time for our body clocks to
adjust. The resulting fatigue, which can last for days, is known as jet
The research team, funded by The Wellcome Trust, was trying to
figure out why people do not instantly adapt. They looked in mice as
all mammals have the same core body clock mechanisms.
They focused on the "master clock" in a part of the brain,
which keeps the rest of the body in sync, called the suprachiasmatic
They were looking for sections of DNA that changed their activity levels in response to light.
They found a huge numbers of genes were
activated, but then a protein called SIK1 went round turning them all
off again. It was acting as a brake by limiting the effect of light.
Experiments to reduce the function of SIK1 meant the mice
could rapidly adjust their body clock when it was shifted six hours -
the equivalent of a flight from the UK to India.
Prof Russell Foster told the BBC: "We reduced levels by
50-60%, which is big enough to get a very, very big effect. What we saw
was the mice would actually advance their clock six hours within a day
[rather than taking six days for untreated mice].
"We've know there's been a brake on the clock for some time,
but we had absolutely no idea what it is, this provides a molecular
basis for jet lag and as a result new targets for potentially developing
He said some mental health disorders including schizophrenia
were linked to an out-of-tune body clock, so these findings may open up
new areas for research.
The brakes are likely to be in place to prevent the body
clock from becoming erratic and being reset by artificial or moon light.
Dr Akhilesh Reddy, a specialist in the body clock, at the
University of Cambridge, was very confident that treatments would follow
as "it is a very drugable target and I would suspect there are lots of
potential drugs already developed".
He told the BBC: "We have known a lot about the basis of jet lag and why it occurs.
"This shows how you can get into the brain and manipulated the clock, which is why this study is important.
"We have drugs which can make the clock shorter or longer,
what we need is to shift it to a new time zone and that is what they