MicroRNA: Function, Detection, and Bioanalysis

Mature microRNAs (miRNAs) are a class of evolutionally conserved, single-stranded, small, endogenously expressed, and non-protein-coding RNAs that act as post-transcriptional regulators of gene expression in a broad range of animals, plants, and viruses. The biogenesis of miRNAs is a multiple step process. miRNAs are initially transcribed in the cell nucleus from intragenic or intergenic regions by RNA polymerase II to form primary miRNAs with length of 1-3 kb. As the miRNA field continues to evolve, it is an essential step to develop efficient and reliable detection strategies for miRNAs toward understanding the functions of miRNAs in diverse regulatory pathways, which eventually influence the development of miRNA-based therapies in diagnostic tests at molecular level and new targets in drug discovery. As for hybridization-based detection, it is difficult to label the short probe for selective detection of miRNAs. Meanwhile, the duplex melting temperature between the probe and its target is low, which sharply decreases the stringency of hybridization and increases the risk of crosshybridization. Mismatch sequence can easily produce a false positive signal.