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Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures
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Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures

Published on: November 11, 2016

mCRY1 and mCRY2 are essential components of the negative limb of the circadian clock feedback loop

K Kume1, M J Zylka, S Sriram

  • 1Laboratory of Developmental Chronobiology, Pediatric Service, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.

Cell
|July 31, 1999
PubMed

Insights

Mouse cryptochrome (mCRY) proteins mCry1 and mCry2 are key components of the circadian clock. These proteins regulate gene expression by inhibiting the CLOCK:BMAL1 transcriptional complex, acting in the negative feedback loop.

Area of Science:

  • * Molecular Biology
  • * Chronobiology
  • * Genetics

Background:

  • * The circadian clock regulates daily biological rhythms.
  • * The core clock mechanism involves transcriptional-translational feedback loops.
  • * The roles of specific clock components like cryptochromes in these loops require elucidation.

Purpose of the Study:

  • * To determine the function of mouse cryptochrome genes (mCry1 and mCry2) in the circadian clock.
  • * To investigate the interaction of mCRY proteins with mPER proteins and their effect on CLOCK:BMAL1 transcription.

Main Methods:

  • * Analysis of mCry1 and mCry2 RNA levels in Clock/Clock mutant mice.
  • * Cellular localization studies of mCRY1 and mCRY2 proteins.
  • * Co-immunoprecipitation assays to study protein interactions.
  • * Luciferase reporter gene assays to assess transcriptional inhibition.

Main Results:

  • * mCry1 and mCry2 RNA levels are reduced in Clock/Clock mutant mice.
  • * mCRY1 and mCRY2 are nuclear proteins that interact with mPER proteins.
  • * mCRY1 and mCRY2 translocate mPER proteins from the cytoplasm to the nucleus.
  • * mCRY1 or mCRY2 alone inhibits CLOCK:BMAL1-mediated transcription.
  • * mPER and mCRY proteins differentially inhibit the transcriptional complex.

Conclusions:

  • * Mouse cryptochromes mCry1 and mCry2 function in the negative limb of the circadian clock feedback loop.
  • * mCRY proteins are essential for the nuclear localization of mPER proteins and inhibition of CLOCK:BMAL1 transcription.
  • * Differential inhibition by mPER and mCRY proteins suggests complex regulatory mechanisms within the clock.

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