The initial hypothesis of Braun et al.  is complemented with an alternative pathway that competes with the miRNA-mediated pathway. Initially, all mRNA start at the state represented by the central green circle and follow one of the two competing paths. The path towards the left (denoted by λ) is exclusive of the miRISC pathway (towards the right, denoted by λR ), and vice versa. The rates λ, µ and ν have been fixed through the fitting performed in Figure 4. The negative control "Control (-)" data result from the decay pattern of the mRNA when only the states represented by the green circles are available.