MicroRNAs are small regulatory RNA molecules that exert post-transcriptional control overexpression of specific target mRNAs. AU-rich elements (AREs) are highly conserved 3'UTR sequences that alter the stability and translation of mRNAs of clinical importance as a rapid and transient response to external and internal changes. We recently demonstrated that a reporter mRNA containing the tumor necrosis factor alpha (TNFalpha) ARE activates translation in response to quiescence via microRNA target sites in the ARE. Further studies revealed that microRNAs in general have the potential to regulate translation in a cell cycle determined manner: in quiescent cells, microRNAs activate translation while in cycling/proliferating cells, microRNAs repress translation.