miRNA-Mediated RNA Activation in Mammalian Cells.

MicroRNA (miRNA or miR) is a small noncoding RNA molecule ~22 nucleotides in size, which is found in plants, animals, and some viruses. miRNAs are thought to primarily down regulate gene expression by binding to 3' untranslated regions of target transcripts, thereby triggering mRNA cleavage or repression of translation. Recently, evidence has emerged that miRNAs can interact with the promoter and activate gene expression. This mechanism, called RNA activation (RNAa), is a process of transcriptional activation where the direct interaction of miRNA on the promoter triggers the recruitment of transcription factors and RNA-Polymerase-II on the promoter to activate gene transcription. To date, very little is known about the mechanism by which miRNA regulates RNA activation (RNAa) and their role in tumor progression. This is an emerging field in RNA biology. In this chapter, we describe the mechanisms utilized by miRNAs to activate transcription.