In the Aug. 1 issue of G&D, a team of Japanese scientists led by Dr. Shigeyuki Yokoyama (RIKEN and the University of Tokyo), presents heretofore the most relevant experimental system of microRNA-mediated translational repression.
“Our cell-free system provides breakthrough in elucidating miRNP function,” according to Dr. Yokoyama.
Their study provides unprecedented insight into how miRNAs repress translation, and helps to resolve the current conflict over the precise mechanism of miRNA action.
Dr. Yokoyama and colleagues developed a cell-free system using extracts from human epithelial cells that were engineered to over-express specific miRNA pathway components. They introduced exogenous let-7 miRNAs and monitored its effects on the translation of luciferase reporter mRNA.
The researchers found that let-7 miRNAs recruited miRNP complexes containing Ago2 and GW182 proteins to target mRNAs, resulting in mRNA deadenylation and translational repression. These findings suggest that miRNAs interfere with the initiation step of translation.
Genes & Development