Before revision:  an increase in the extrinsic noise shifts the range of target transcription rates that allow bimodality towards higher values, (iii) the protein half-life may buffer bimodal mRNA preventing its distribution from becoming bimodal and that (iv) in a noisy environment different targets may cross-regulate each other's bimodal distribution when competing for a shared pool of miRNAs even if the miRNA regulation is small .
After revision:  an increase in the extrinsic noise shifts the range of target transcription rates that allow bimodality towards higher values, (iii) the protein half-life .