MicroRNA-mediated regulation of gene expression is characterised by some
distinctive features that set it apart from unregulated and transcription
factor-regulated gene expression. Recently, a mathematical model has been
proposed to describe the dynamics of post-transcriptional regulation by
microRNAs. The model explains the observations made in single cell experiments
quite well. In this paper, we introduce some additional features into the model
and consider two specific cases. In the first case, a non-cooperative positive
feedback loop is included in the transcriptional regulation of the target gene
expression. In the second case, a stochastic version of the original model is
considered in which there are random transitions between the inactive and
active expression states of the gene. In the first case we show that
bistability is possible in a parameter regime, due to the presence of a
non-linear protein decay term in the gene expression dynamics. In the second
case, we derive the conditions for obtaining stochastic binary gene expression.
We find that this type of gene expression is more favourable in the case of
regulation by microRNAs as compared to the case of unregulated gene expression.
The theoretical predictions relating to binary gene expression are
experimentally testable.Comment: 10 Pages, 5 Figure
