Models of mRNA translational repression and translation initiation complexes. (a) mRNAs are translationally repressed by RBPs that bind sequence recognition motifs in the 3′UTR. Protein-protein interactions with 4EBP-eIF4E-mRNA form stable mRNP complexes that inhibit the recruitment of eIF4E-bound mRNA to eIF4G, eIF4A (an mRNA helicase), and the ribosome. (b) Model of cap-dependent translation initiation utilizing the cap-binding protein eIF4E. Cap-bound mRNAs are recruited to the 40S ribosomal subunit by association with eIF4G and PABP. Association with eIF2 and eIF3 completes the 48S preinitiation complex. (c) Model of cap-independent translation. The “short” isoform of eIF4G lacking an eIF4E-binding domain is still capable of recruiting mRNA to the 40S ribosomal subunit with eIFs by binding directly to the 5′UTR.