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Cell Biology: Researchers Find the Reset Button for the Fruit Fly Clock

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Science  22 Mar 1996:
Vol. 271, Issue 5256, pp. 1671-1672
DOI: 10.1126/science.271.5256.1671


One of the more puzzling observations concerning the circadian clock of the fruit fly concerns how it can be reset by light. If the light comes on early at night, it sets the clock back, but if it comes on late it pushes the clock forward. Now four independent groups, two of which describe their work in this issue, have solved the puzzle. They've found that a recently discovered clock protein called TIM (for timeless) is the key. TIM and its partner PER (for period) control the clock by cycling up and down, reaching peak concentrations at night. Light destroys TIM, and when this happens early in the evening when TIM and PER are still being made, it just delays the clock. But later at night, when TIM and PER levels are falling anyway, it accelerates this effect, advancing the clock.