The Utility of Paradoxical Components in Biological Circuits

Yuval Hart, Uri Alon*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

118 Scopus citations


A recurring theme in biological circuits is the existence of components that are antagonistically bifunctional, in the sense that they simultaneously have two opposing effects on the same target or biological process. Examples include bifunctional enzymes that carry out two opposing reactions such as phosphorylating and dephosphorylating the same target, regulators that activate and also repress a gene in circuits called incoherent feedforward loops, and cytokines that signal immune cells to both proliferate and die. Such components are termed "paradoxical", and in this review we discuss how they can provide useful features to cell circuits that are otherwise difficult to achieve. In particular, we summarize how paradoxical components can provide robustness, generate temporal pulses, and provide fold-change detection, in which circuits respond to relative rather than absolute changes in signals.

Original languageAmerican English
Pages (from-to)213-221
Number of pages9
JournalMolecular Cell
Issue number2
StatePublished - 24 Jan 2013
Externally publishedYes

Bibliographical note

Funding Information:
U.A. is the incumbent of the Abisch-Frenkel Professorial Chair. U.A. thanks the European Research Council (FP7) and the Israel Science Foundation for their support.


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