ИСТИНА

The ribosome flow model (RFM) is a deterministic model for mRNA translation. Each RFM has an input that controls its initiation rate and an output that represents the ribosome exit rate (and thus the protein production rate) at the 3’ end of the mRNA molecule. As a first step towards studying the interconnected production of proteins in the many mRNAs moelcules in the cell, we consider here layered feedforward networks of RFMs, where the output of an RFM can be connected to the inputs of other RFMs in the next layer. We show that the entire network converges to a steady-state that depends only on the initiation and transition rates in all the RFMs, but not on the initial condition. We also show that the problem of dividing the output of one RFM between the inputs of the consecutive RFMs in a way that maximizes the total production rate is a convex optimization problem. We describe the implications of our results to several aspects of translation.