Key result
Paip1 binds directly to the eIF3g subunit of eukaryotic translation initiation factor 3 to stimulate translation, likely by stabilizing the interaction between PABP and eIF4G.
This basic science study demonstrates that the eIF3-Paip1 interaction promotes translation, likely by stabilizing the interaction between PABP and eIF4G to circularize mRNA.
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Paip1-eIF3g interaction may enhance translation efficiency; leaves open its relevance to cardiac protein synthesis and disease models.
Poly(A)-binding protein (PABP) stimulates translation initiation by binding simultaneously to the mRNA poly(A) tail and eukaryotic translation initiation factor 4G (eIF4G). PABP activity is regulated by PABP-interacting (Paip) proteins. Paip1 binds PABP and stimulates translation by an unknown mechanism. Here, we describe the interaction between Paip1 and eIF3, which is direct, RNA independent, and mediated via the eIF3g (p44) subunit. Stimulation of translation by Paip1 in vivo was decreased upon deletion of the N-terminal sequence containing the eIF3-binding domain and upon silencing of PABP or several eIF3 subunits. We also show the formation of ternary complexes composed of Paip1-PABP-eIF4G and Paip1-eIF3-eIF4G. Taken together, these data demonstrate that the eIF3-Paip1 interaction promotes translation. We propose that eIF3-Paip1 stabilizes the interaction between PABP and eIF4G, which brings about the circularization of the mRNA.
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Martineau et al. (2008) studied this question. Paip1 vs. Control vector / siRNA controls was evaluated on Translation stimulation (Renilla luciferase activity). Paip1 binds directly to the eIF3g subunit of eukaryotic translation initiation factor 3 to stimulate translation, likely by stabilizing the interaction between PABP and eIF4G.
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