Light causes breakdown of TIMELESS protein and resets the fruit fly's internal clock

The TIM protein may be rapidly degraded after exposure to light.

• Two genes, period (per) and timeless (tim), are essential for circadian rhythm production in fruit flies.
• The proteins produced by these genes, PER and TIM, interact physically.
• The timing of PER and TIM's association and movement into the nucleus may regulate their own production through a feedback loop.
• TIM accumulates rhythmically in the nuclei of both the eyes and brain's pacemaker cells.
• Light pulses at different times can advance or delay the phase of TIM rhythms, which corresponds with changes in behavioral rhythms.

Simplified