Structural and Functional Organization of miRNAs

Abstract

Understanding human gene regulation is of pivotal importance in the field of genetics and genomics, including pharmacogenomics. Increasingly many described effects of natural genetic variation are exerted on the level of gene regulation. A novel mechanism of regulation of gene expression involving the so called the non coding microRNAs (miRNAs) has attracted a lot of attentions during the last years. MicroRNAs are a class of endogenous small regulatory RNA molecules that target mRNAs and trigger either translation repression or mRNA degradation. They are known to regulate genes involved in the control of development, proliferation, apoptosis, stress response, and tumourigenesis. They are transcribed as individual units, polycistronic clusters or in concert with a protein coding host gene. The picture emerging reveals a widespread influence on many cellular processes. The analysis of miRNA regulation and its involvement in diseases is hampered by the great redundancy of miRNA genes and the unknown complexity in the modular regulatory mechanisms they may exert. An individuals genetic background will in addition influence this regulation. This review provides insights into the complexity of human miRNA organization, and may facilitate future analysis of miRNA expression as well as studies of the modular regulatory effects of miRNAs.