The Chicken or the Egg: MicroRNA-Mediated Regulation of mRNA Translation or mRNA Stability  Arina D. Omer, Maja M. Janas, Carl D. Novina  Molecular Cell  Volume 35, Issue 6, Pages 739-740 (September 2009) DOI: 10.1016/j.molcel.2009.09.003 Copyright © 2009 Elsevier Inc. Terms and Conditions

Figure 1 Model of miRNA Function in Mammalian Cells Ago-miRNA-containing complexes repress translation initiation by blocking 40S subunit recruitment to target mRNAs or 60S subunit joining to recruited 40S subunits positioned at AUG (upper right). The cell interprets translationally repressed mRNAs as defective (not translatable) and translocates these mRNAs to P bodies (solid line down) where mRNAs are destabilized through recruitment of deadenylation complexes (bottom right). mRNAs can be degraded by the 5′→3′ decay pathway (bottom center) or, by mechanisms that are poorly defined, stored (bottom left) and returned later (dashed line up) to the pool of actively translating mRNAs (top left). Other mechanisms of miRNA-mediated translational repression have been reported that do not target the initiation step (upper right). It is unclear if deadenylation plays a role in these mechanisms of translational repression at the postinitiation stage of translation. Molecular Cell 2009 35, 739-740DOI: (10.1016/j.molcel.2009.09.003) Copyright © 2009 Elsevier Inc. Terms and Conditions