Fig. 1.

Schematic comparison of direct transcriptional regulation (DTR) and indirect translational regulation (ITR) schemes. (a) In direct transcriptional regulation (DTR), activator (or repressor) TFs, depicted as green squares and present at concentration c, interact with (potentially multiple, not necessarily identical) TF binding regions to activate (repress) expression of the regulated gene g. (b) In the indirect translational regulation (ITR) scenario, input molecules (green squares) bind to mRNAs m of protein y (red chain) to make the mRNA unaccessible for translation (gray oval). Translation can proceed from unbound mRNA molecules, giving rise to proteins y (red stars). These proteins act as repressors (or activators) for gene g; the overall mapping from c to g is thus activating (repressing) in both scenarios.