A light-entrainment mechanism for the Drosophila circadian clock

Nature. 1996 Mar 14;380(6570):129-35. doi: 10.1038/380129a0.


Biochemical studies indicate that the Drosophila timeless protein (Tim) is a stoichiometric partner of the period protein (Per) in fly head extracts. A Per-Tim heterodimeric complex explains the reciprocal autoregulation of the proteins on transcription. The complex is under clock control, and many circadian features of the Tim cycle resemble those of the Per cycle. However, Tim is rapidly degraded in the early morning or in response to light, releasing Per from the complex. The Per-Tim complex is a functional unit of the Drosophila circadian clock, and Tim degradation may be the initial response of the clock to light.

MeSH terms

  • Animals
  • Biopolymers
  • Centrifugation, Density Gradient
  • Chromatography, Gel
  • Circadian Rhythm / genetics
  • Circadian Rhythm / physiology*
  • Drosophila / genetics
  • Drosophila / physiology*
  • Drosophila Proteins*
  • Gene Expression Regulation
  • Light
  • Models, Biological
  • Nuclear Proteins / genetics
  • Nuclear Proteins / isolation & purification
  • Nuclear Proteins / physiology*
  • Nuclear Proteins / radiation effects
  • Period Circadian Proteins
  • Precipitin Tests
  • Proteins / genetics
  • Proteins / physiology*
  • Proteins / radiation effects
  • Transcription, Genetic


  • Biopolymers
  • Drosophila Proteins
  • Nuclear Proteins
  • PER protein, Drosophila
  • Period Circadian Proteins
  • Proteins
  • tim protein, Drosophila