Related Experiment Video

Updated: Aug 11, 2026

In Vitro Bioluminescence Assay to Characterize Circadian Rhythm in Mammary Epithelial Cells
11:56

In Vitro Bioluminescence Assay to Characterize Circadian Rhythm in Mammary Epithelial Cells

Published on: September 28, 2017

Feedback repression is required for mammalian circadian clock function

Trey K Sato1, Rikuhiro G Yamada, Hideki Ukai

  • 1Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Dr., San Diego, California 92121, USA.

Nature Genetics
|February 14, 2006
PubMed

Insights

The circadian clock requires transcriptional feedback repression for proper function. This study identifies mutations in CLOCK and BMAL1 proteins that disrupt this feedback, leading to arrhythmic cellular behavior.

Area of Science:

  • Chronobiology
  • Molecular genetics
  • Mammalian cell biology

Background:

  • Circadian rhythms are endogenous biological processes that regulate daily cycles.
  • Transcriptional feedback repression is a key mechanism in circadian clock function.
  • Previous studies lacked direct evidence for the necessity of this repression.

Purpose of the Study:

  • To identify specific mutations in CLOCK and BMAL1 that impair CRYPTOCHROME-mediated transcriptional repression.
  • To provide direct evidence for the requirement of transcriptional feedback in mammalian circadian clock function.

Main Methods:

  • Developed a molecular genetic screen in mammalian cells.
  • Identified CLOCK and BMAL1 mutants uncoupled from CRY-mediated repression.
  • Analyzed physical interactions between mutant proteins and CRY.
  • Assessed circadian phenotypes using population and single-cell assays.

Main Results:

  • Mutations in the PER-ARNT-SIM domain of CLOCK and the C terminus of BMAL1 reduced physical interaction with CRY.
  • These mutations led to synergistic insensitivity to CRY-mediated repression.
  • Coexpression of mutant proteins resulted in arrhythmic phenotypes in cultured fibroblasts.

Conclusions:

  • CRYPTOCHROME-mediated repression of the CLOCK/BMAL1 complex is essential for maintaining circadian rhythmicity.
  • This study provides formal proof for the requirement of transcriptional feedback in mammalian clock function.
  • Identified specific domains and interactions critical for circadian clock regulation.

More Related Videos

Monitoring Cell-autonomous Circadian Clock Rhythms of Gene Expression Using Luciferase Bioluminescence Reporters10:38

Monitoring Cell-autonomous Circadian Clock Rhythms of Gene Expression Using Luciferase Bioluminescence Reporters

Published on: September 27, 2012

In Vivo Monitoring of Circadian Clock Gene Expression in the Mouse Suprachiasmatic Nucleus Using Fluorescence Reporters07:44

In Vivo Monitoring of Circadian Clock Gene Expression in the Mouse Suprachiasmatic Nucleus Using Fluorescence Reporters

Published on: July 4, 2018

Related Concept Videos

Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
Co-activators and Co-repressors02:04

Co-activators and Co-repressors

Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
Eukaryotic Transcription Inhibitors01:52

Eukaryotic Transcription Inhibitors

Certain biochemical processes, such as embryonic development and cell growth regulation, depend on the repression of specific genes. DNA binding proteins known as eukaryotic transcription inhibitors regulate the repression of gene expression in eukaryotes. The presence of these inhibitors at the required location and time in the cell is triggered by the presence of hormones and additional signals from other cells.
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
Repressible Operon: trp Operon01:21

Repressible Operon: trp Operon

The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
Transcriptional Regulation: Riboswitches01:23

Transcriptional Regulation: Riboswitches

Riboswitches are RNA elements that regulate gene expression by altering their secondary structures in response to specific effector molecules. These elements, located in the leader regions of certain mRNAs, act as transcriptional regulators by toggling between alternative conformations to control downstream gene expression. Riboswitch-mediated regulation is a precise mechanism for modulating biosynthetic pathways, as exemplified by the riboflavin biosynthesis pathway in Bacillus...
Master Transcription Regulators02:23

Master Transcription Regulators

Master transcription regulators are regulatory proteins that are predominantly responsible for regulating the expression of multiple genes. Often these genes work in concert to drive a  complex process. Activation of a master transcription regulator can lead to a cascade of transcriptional activation necessary for that outcome. These regulators can directly bind to the regulatory sequences of the various genes involved, or they can indirectly regulate transcription by binding to regulatory...