Eukaryotic Translation Initiation Factor 3I (EIF3I)

Eukaryotic initiation factor 3 (eIF3) is the largest of the eIFs and consists of at least 10 nonidentical subunits in mammals. TRIP1 (TGF-beta receptor-interacting protein-1), a protein that specifically associates with RII. The association with RII requires RII's kinase activity, suggesting that receptor autophosphorylation creates a binding site for TRIP1. Since TRIP1 is phosphorylated on serine and threonine by the receptor kinase, the authors proposed that TRIP1 plays a role in TGF-beta signaling. Northern blot analysis indicated that TRIP1 was expressed as a 1.6-kb mRNA in all human fetal tissues tested. In mouse embryos, the immunolocalization patterns of TRIP1 and RII were well correlated, further supporting a functional correlation between both proteins.