Micro-ARN : oncogènes et suppresseurs de tumeurs

Abstract

microRNAs constitute one of the most important discovery in the past few years in the field of gene expression regulation. They can precisely regulate the expression of a specific protein by inhibiting its translation and/or promoting the degradation of its mRNA. In several cancers, the expression of some microRNAs is misregulated, pointing toward the existence of microRNAs with oncogenic or tumour suppressor properties. The miR-17-92 miRNA cluster has been reported to have a pro-oncogenic role in a mouse model system of Myc-induced B cell lymphoma. Some of its targets mRNAs code for proteins with pro-apoptotic or anti-proliferative functions, which shed some light on the mechanism of action of this cluster. On the other hand, a tumour suppressor miRNA like let-7 targets mRNAs coding for oncogenes and is frequently down-regulated in cancers. The finding that c-Myc controls the expression of several of these microRNAs reveals new information on how misregulation of this proto-oncogene can promote tumorigenesis.