Figure 1.

Regulation of eukaryotic mRNA translation occurs at numerous control points. Recognition of 3' UTR sequence or structural elements (green and red boxes) by RNA-binding proteins leads to either activation or repression of translation, often through alteration of the 3' poly(A) tail or through interactions with proteins that bind at the 5' terminal cap structure (that is, the initiation factor eIF4E or cap-binding proteins). Repression of translation by miRNAs can occur through inhibition of translation initiation or elongation, and may also lead to changes in the status of the mRNA 3' poly(A) tail. Elements found within the mRNA 5' UTR (yellow box) can bind regulatory proteins that repress translation by inhibiting 48S ribosome scanning. Global regulation of mRNA translation is commonly achieved through modification of the translational apparatus (that is, by phosphorylation of the translation initiation factors eIF2α and eIF4E) and the ribosome itself, or modulation of protein partner binding affinities (such as the phosphorylation of the eIF4E-binding proteins). Translation can be initiated independent of the mRNA 5' cap through a structured internal ribosome entry site (IRES) in the 5' UTR whose efficiency in initiating translation is, in turn, modulated by trans-acting factors (ITAFs).