Fig. 6 Target regulation by microRNAs (as discussed by Sengupta et al84). (a) After binding to the mRNA, miRNA immediately activates the target mRNA degradation and causes target repression. (b) Low target degradation after miRNA binding and translation of miRNA bound complex can result in target upregulation.
They predicted that the stabilization of the target mRNA due to miRNA binding and translation of protein from miRNA bound mRNA are important to achieve the target protein upregulation by the miRNA.105 The above-mentioned studies suggest that translation upregulation is possible when the miRNA:mRNA complex is somehow stabilized and the degradation of mRNA along with the translation inhibition is not high from the corresponding complex (Fig. 6b ). It was further suggested by certain studies that the presence of the regulatory sequences such as ARE binding motifs, poly C motifs can facilitate the binding of RNA binding proteins, which stabilizes mRNAs and upregulates translation.106,107