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Structure and function of the feed-forward loop network motif
 

Summary: Structure and function of the feed-forward loop
network motif
S. Mangan and U. Alon
Departments of Molecular Cell Biology and Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
Edited by Arnold J. Levine, Institute for Advanced Study, Princeton, NJ, and approved August 25, 2003 (received for review June 22, 2003)
Engineered systems are often built of recurring circuit modules
that carry out key functions. Transcription networks that regulate
the responses of living cells were recently found to obey similar
principles: they contain several biochemical wiring patterns,
termed network motifs, which recur throughout the network. One
of these motifs is the feed-forward loop (FFL). The FFL, a three-gene
pattern, is composed of two input transcription factors, one of
which regulates the other, both jointly regulating a target gene.
The FFL has eight possible structural types, because each of the
three interactions in the FFL can be activating or repressing. Here,
we theoretically analyze the functions of these eight structural
types. We find that four of the FFL types, termed incoherent FFLs,
act as sign-sensitive accelerators: they speed up the response time
of the target gene expression following stimulus steps in one
direction (e.g., off to on) but not in the other direction (on to off).

  

Source: Alon, Uri - Departments of Molecular Cell Biology & Physics of Complex Systems, Weizmann Institute of Science

 

Collections: Biology and Medicine