FIGURE 8.

Model for SLBP-mediated translation. SLBP binds the stem–loop structure in the 3′ UTR of histone mRNAs. SLBP interacts with a novel factor X that in turn binds to eIF4E at the m⁷GpppG cap (indicated as a black circle), leading to circularization of histone mRNA. Additionally, SLBP interacts with subunit h of eIF3 and with Paip1. Paip1 binds eIF4A and is predicted to bind eIF3. These interactions may play a minor role by either stabilizing end-to-end complexes containing SLBP-X-eIF4E or by aiding the recruitment of the small ribosomal subunit (40S). eIF4G may or may not be present in the complex (see Discussion). (ORF) Open reading frame. The figure is schematic and does not depict all the factors involved in translation initiation nor is it meant to indicate the full extent of RNA–protein and protein–protein interactions.