The observation that, through a titration mechanism, microRNAs (miRNAs) can
act as mediators of effective interactions among their common targets
(competing endogenous RNAs or ceRNAs) has brought forward the idea ('ceRNA
hypothesis') that RNAs can regulate each other in extended 'cross-talk'
networks. Such an ability might play a major role in post-transcriptional
regulation (PTR) in shaping a cell's protein repertoire. Recent work focusing
on the emergent properties of the cross-talk networks has emphasized the high
flexibility and selectivity that may be achieved at stationarity. On the other
hand, dynamical aspects, possibly crucial on the relevant time scales, are far
less clear. We have carried out a dynamical study of the ceRNA hypothesis on a
model of PTR. Sensitivity analysis shows that ceRNA cross-talk is dynamically
extended, i.e. it may take place on time scales shorter than those required to
achieve stationairity even in cases where no cross-talk occurs in the steady
state, and is possibly amplified. Besides, in case of large, transfection-like
perturbations the system may develop strongly non-linear, threshold response.
Finally, we show that the ceRNA effect provides a very efficient way for a cell
to achieve fast positive shifts in the level of a ceRNA when necessary. These
results indicate that competition for miRNAs may indeed provide an elementary
mechanism to achieve system-level regulatory effects on the transcriptome over
physiologically relevant time scales.Comment: Main text: 10 pages, 13 figures. Supporting Text: 3 pages, 6 figure