Biological and Clinical Implications of Micro-RNA in the Pathogenesis of Cancer and Human Diseases

MicroRNAs (miRNAs) are a group of small RNAs, with around 19 to 25 nucleotides, which results from cleavage of larger noncoding RNAs. They act as regulators of gene expression posttranscriptionally both in plants and in animals. The first miRNA was discovered in 1993 by Victor Ambros and colleagues Rosalind Lee and Rhonda Feinbaum. Subsequently, many more short regulatory RNAs were identified in almost all multicellular organisms, including flowering plants, worms, flies, fish, mammals and in single cellular algae and DNA viruses. More than 500 human miRNAs have been experimentally identified till date. It has been studied by computational predictions of miRNA that up to 30% of human protein coding genes may be regulated by miRNAs. This makes miRNAs one of the most abundant groups of regulatory genes in human body. MicroRNAs are now perceived as a key layer of posttranscriptional control within the networks of gene regulation.