  Gene expression is a noisy process and several mechanisms, both
transcriptional and posttranscriptional, can stabilize protein levels in cells.
Much work has focused on the role of miRNAs, showing in particular that
miRNA-mediated regulation can buffer expression noise for lowly expressed
genes. Here, using in silico simulations and mathematical modeling, we
demonstrate that miRNAs can exert a much broader influence on protein levels by
orchestrating competition-induced crosstalk between mRNAs. Most notably, we
find that miRNA-mediated cross-talk (i) can stabilize protein levels across the
full range of gene expression rates, and (ii) modifies the correlation pattern
of co-regulated interacting proteins, changing the sign of correlations from
negative to positive. The latter feature may constitute a potentially robust
signature of the existence of RNA crosstalk induced by endogenous competition
for miRNAs in standard cellular conditions.
