Cloning microRNAs from mammalian tissues

MicroRNAs (miRNAs) are ubiquitous regulators of gene expression in plants and animals. Their distinctive structure, as very short RNAs with a 5'-phosphate and 3'-hydroxyl group, has enabled the development of protocols to clone miRNAs. After enrichment of these small molecules by size, serial ligation of adapter oligonucleotides to each terminus allows amplification using reverse transcription (RT)-polymerase chain reaction (PCR). Plasmid cloning of multiple miRNA sequences and subsequent DNA sequence analysis enable both bioinformatic characterization of the various miRNAs and experimental validation of their accumulation in cells.