Figure 7.

Model of the specialized translation of PCE-containing mRNAs and assembly of mTOR-resistant RNP complexes. Model comparing nuclear assembly of cap-dependent mRNPs. Left, PCE-bearing mRNAs bind NCBP1-NCBP3 at the 5′-cap and RHA at the PCE and experience the exchange of PABPN to PABPC1. RHA-NCBP1-NCBP3 mRNPs facilitate assembly of JUND polysomes whether the eIF4E-mRNPs are active or inhibited by 4E-BP1. Right, canonical engagement of NCBP1-NCBP2 at the 5′-cap is depicted by mRNA lacking PCE. Consequential to nuclear export, CBC undergoes exchange to eIF4E, which engages eIF4G and other factors to assemble polysomes. In common, both mRNPs experience the exchange of PABPN to PABPC1. The eIF4E-eIF4G–dependent polysome assembly is abrogated upon the inhibition of mTOR because of down-regulated eIF4E activity.