Oscillatory dynamics in a double activator motif

Abstract

Biological oscillators, specially those that constitute the circadian clock, have been extensively modelled as coupled feedback loops of positive and negative elements in gene regulatory circuits. The presence of a negative feedback loop is a necessary condition for the onset of oscillations, and different mechanistic implementations have been modelled, such as transcriptional repression (such as CRY/PER down-regulating activation by CLOCK:BMAL1 in the mammalian clock) or by enhancing proteolysis. It is also a characteristic feature of transcriptional control in clock systems that conserved cis-regulatory sequences (such as E- and D-boxes) are competitively bound by transctiption factors. Using this feature, we propose a new duplicated autoregulated motif where competition for the same promoters by differentially activating transctiption factors drives oscillations.

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