Network to fit the data NOT1 & PAN3 KD. After fixing the rates µ, λ and ν from the fitting of the negative decay pattern in Figure 4, we use this network in order to model the decay pattern when miRNA is expressed but NOT1 and PAN3 are knocked down. In order to perform this fit, however, we must add a new transition to degradation after the binding of the miRISC (rightmost transition to degradation). This new transition might contain a complex set of processes which are most likely independent of deadenylation. In the light of recent results, this arrow could include deadenylation-independent decapping [23, 24].