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Related Experiment Videos

A coherent feed-forward loop with a SUM input function prolongs flagella expression in Escherichia coli.

Shiraz Kalir1, Shmoolik Mangan, Uri Alon

  • 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel.

Molecular Systems Biology
|May 27, 2006
PubMed
Summary

The sum input function feed-forward loop (SUM-FFL) in E. coli flagella networks prolongs gene expression after signal loss. This gene circuit protects flagella production from temporary signal interruptions.

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Area of Science:

  • Systems Biology
  • Molecular Biology
  • Genetics

Background:

  • Gene regulation relies on recurring network motifs.
  • Coherent feed-forward loops (FFLs) are key motifs, with AND-gated FFLs acting as delay elements.
  • The function of SUM-FFLs remains less understood.

Purpose of the Study:

  • To investigate the dynamics and function of the coherent FFL with a sum input function (SUM-FFL).
  • To analyze the SUM-FFL within the Escherichia coli flagella gene-regulation network.

Main Methods:

  • High-resolution gene expression measurements.
  • Analysis of the flagella gene-regulation network in E. coli.
  • Investigating the role of the FlhDC and FliA regulators.

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Main Results:

  • The SUM-FFL prolongs flagella gene expression after the master regulator (FlhDC) is deactivated.
  • This motif protects flagella production against transient signal loss.
  • The SUM-FFL functions as predicted, even within complex feedback systems.

Conclusions:

  • The SUM-FFL acts as a signal-deactivation delay element, contrasting with the AND-FFL's activation delay.
  • This mechanism ensures robust flagella production in E. coli.
  • SUM-FFLs may perform similar protective functions in gene networks across diverse organisms.