dCLOCK is present in limiting amounts and likely mediates daily interactions between the dCLOCK-CYC transcription factor and the PER-TIM complex

Kiho Bae, Choogon Lee, Paul E. Hardin, Isaac Edery

Research output: Contribution to journalArticlepeer-review

110 Scopus citations

Abstract

In Drosophila melanogaster four circadian clock proteins termed PERIOD (PER), TIMELESS (TIM), dCLOCK (dCLK), and CYCLE (CYC/dBMAL1) function in a transcriptional feedback loop that is a core element of the oscillator mechanism. dCLK and CYC are members of the basic helix-loop-helix (bHLH)/PAS (PER-ARNT-SIM) superfamily of transcription factors and are required for high-level expression of per and tim and repression of dClk, whereas PER and TIM inhibit dCLK-CYC-mediated transcription and lead to the activation of dClk. To understand further the dynamic regulation within the circadian oscillator mechanism, we biochemically characterized in vivo-produced CYC, determined the interactions of the four clock proteins, and calculated their absolute levels as a function of time. Our results indicate that throughout a daily cycle the majority of the dCLK present in adult heads stably interacts with CYC, indicating that CYC is the primary in vivo partner of dCLK. dCLK- CYC dimers are bound by PER and TIM during the ate evening and early morning, suggesting the formation of a tetrameric complex with impaired transcriptional activity. Although dCLK is present in limiting amounts and CYC is by far the most abundant of the four clock proteins that have been examined, PER and TIM appear to interact preferentially with dCLK. Our results suggest that dCLK is the main component regulating the daily abundance of transcriptionally active dCLK-CYC complexes.

Original languageEnglish (US)
Pages (from-to)1746-1753
Number of pages8
JournalJournal of Neuroscience
Volume20
Issue number5
DOIs
StatePublished - Mar 1 2000

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)

Keywords

  • Circadian rhythms
  • Clock proteins
  • Drosophila
  • PAS
  • Protein- protein interactions
  • Transcription

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