MicroRNA with a MacroFunction.

With the advent of microRNA (miRNA) we are compelled to revise our understanding of the mechanisms underlying gene regulation during health and disease. A miRNA is approximately 21 ribonucleotides-long, genetically encoded, with a potential to recognize multiple mRNA targets guided by sequence complementarity and RNA-binding proteins. This class of molecules is functionally versatile, with the capacity to specifically inhibit translation initiation or elongation, as well as, induce mRNA degradation, through predominantly targeting the 3'-untranslated regions of mRNA. Early on it was realized that the levels of individual miRNA varied under different developmental, biological, or pathological conditions, thus, implicating these molecules in normal and pathological cellular attributes. In this article we will share our views on how the functions of miRNA conform to our existing knowledge on post-transcriptional regulation of gene expression and disease mechanisms, and their potential as biomarkers and therapeutic targets in diseases.