Translation of Eukaryotic Translation Initiation Factor 4GI (eIF4GI) Proceeds from Multiple mRNAs Containing a Novel Cap-dependent Internal Ribosome Entry Site (IRES) That Is Active during Poliovirus Infection

摘要: Eukaryotic translation initiation factor 4GI (eIF4GI) is an essential scaffolding protein required to recruit the 43 S complex 5′-end of mRNA during initiation. We have previously demonstrated that eIF4GI expression translationally regulated. This regulation mediated by cis-acting RNA elements, including upstream open reading frame and IRES directs synthesis five isoforms via alternative AUG codon selection. Here, we further characterize function show expressed from several distinct mRNAs vary alternate promoter use splicing. Several variants contain element. found activity mapped multiple regions within sequence, but not 5′-UTR per se. However, enhanced in vivo played a role The was active when transfected into cells form, thus, does require nuclear processing events for its function. be dependent upon presence, cis, 5′ m7guanosine-cap. Despite this requirement, activated 2A protease cleavage eIF4GI, vitro, retained ability promote poliovirus-mediated inhibition cap-dependent translation. These data indicate intact de novo suggesting can continue under stress or infection conditions where cleaved.