Structure of eIF4E in Complex with an eIF4G Peptide Supports a Universal Bipartite Binding Mode for Protein Translation

Abstract

The association-dissociation of the cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) with eIF4G is a key control step in eukaryotic translation. The paradigm on the eIF4E-eIF4G interaction states that eIF4G binds to the dorsal surface of eIF4E through a single canonical alpha-helical motif, while metazoan eIF4E-binding proteins (m4E-BPs) advantageously compete against eIF4G via bimodal interactions involving this canonical motif and a second noncanonical motif of the eIF4E surface. Metazoan eIF4Gs share this extended binding interface with m4E-BPs, with significant implications on the understanding of translation regulation and the design of therapeutic molecules. Here we show the high-resolution structure of melon (Cucumis melo) eIF4E in complex with a melon eIF4G peptide and propose the first eIF4E-eIF4G structural model for plants. Our structural data together with functional analyses demonstrate that plant eIF4G binds to eIF4E through both the canonical and noncanonical motifs, similarly to metazoan eIF4E-eIF4G complexes. As in the case of metazoan eIF4E-eIF4G, this may have very important practical implications, as plant eIF4E-eIF4G is also involved in a significant number of plant diseases. In light of our results, a universal eukaryotic bipartite mode of binding to eIF4E is proposed.The initiation of protein synthesis is a key control and highly regulated step in eukaryotic gene expression (Sonenberg and Hinnebusch, 2009). Translation initiation leads to the assembly of the large (60S) and small (40S) ribosomal subunits into an active 80S ribosome that is able to locate the correct start codon of the mRNA molecule. This is facilitated by the coordinated actions of at least 12 protein initiation factors (Browning, 2004;Jackson et al., 2010;Hinnebusch, 2011;Hinnebusch and Lorsch, 2012; Browning and BaileySerres, 2015). In cap-dependent translation, binding of the eukaryotic translation initiation factor 4F (eIF4F) to the 7-methyl guanosine cap (m 7 G cap) at the 59 end of mRNA drives the attachment of the mRNA to the ribosomal 43S preinitiation complex. In mammals, eIF4F is built by three proteins: the mRNA 59 cap binding protein eIF4E, the RNA helicase eIF4A, and the scaffolding protein eIF4G, which contains binding domains for eIF4E, eIF4A, eIF3, and poly(A)-binding protein (PABP; Marcotrigiano et al., 1997;Pestova et al., 2001;Gross et al., 2003). In plants, purified eIF4F heterodimers contain eIF4E and eIF4G (Hinnebusch and Lorsch, 2012); plant eIF4A appears to be loosely associated and is therefore easily lost during purification (Lax et al., 1986). EIF4G associates with eIF3, recruiting the 40S subunit of the ribosome and initiating scanning of the mRNA in the 59 to 39 direction (Jackson et al., 2010;Park et al., 2011). EIF4G additionally binds simultaneously to eIF4E and PABP, the latter being able to interact with the mRNA poly(A) tail (Aitken and Lorsch, 2012; Browning and BaileySerres, 2015), resulting in a transient circularization of the mRNA.Higher plants contain an addit...

A Novel Interaction Network Used by Potyviruses in Virus–Host Interactions at the Protein Level

“…Instead, recent data indicate that VPg can compete with 4E for capped RNAs to inhibit host translation [11]. Plant eIF4Gs bind to 4E via their canonical 4E-binding motif but also via a second non-canonical motif consisting of hydrophobic residues, which connect to a dorsal and a lateral hydrophobic surface of 4E, respectively [18]. The non-canonical motif of eIF4G strengthens the 4E-eIF4G interaction [18].…”

“…Plant eIF4Gs bind to 4E via their canonical 4E-binding motif but also via a second non-canonical motif consisting of hydrophobic residues, which connect to a dorsal and a lateral hydrophobic surface of 4E, respectively [18]. The non-canonical motif of eIF4G strengthens the 4E-eIF4G interaction [18]. Mutations in the lateral domain of 4E can compromise potyvirus infection and are involved in the VPg interaction [16].…”

“…The scaffold protein eIF4G contains a specific motif for 4E binding with a consensus sequence YXXXXLΦ, where X is a variable amino acid and Φ is a hydrophobic residue [17]. In addition to this canonical motif, recent data indicate that 4G interacts with 4E via a second, non-canonical motif at the lateral surface of 4E that strengthens the interaction [18]. eIF4G binds to eIF4E and eIF(iso)4G binds to eIF(iso)4E to form the host eIF4F and eIF(iso)4F complexes, respectively, which also include the ATP-dependent RNA helicase eIF4A.…”

Discovery and characterization of conserved binding of eIF4E 1 (CBE1), a eukaryotic translation initiation factor 4E–binding plant protein

“…BTF3 lacks a canonical eIF4E-binding motif and the proposed eIF4E-binding site of LOX2 shows poor evolutionary conservation ( Fig. S1) (18).…”

Trans‐species synthetic gene design allows resistance pyramiding and broad‐spectrum engineering of virus resistance in plants

“…Significantly, in our study, eIF4E1 R complementation restores full susceptibility to BMYV while it triggers full resistance to BWYV-USA, which could be of interest for sugarbeet breeding programmes. Recently, potyvirus VPg has been suggested to interact with host eIF4E through a conserved noncanonical 4E-binding domain (Miras et al, 2017) which interestingly does not seem to be conserved in VPg from other groups of ssRNA+ viruses. Other viruses are likely to recruit eIF4E through different structural binding domains and would therefore only be marginally affected by potyvirus-specific nonsynonymous AA changes in eIF4E regions I and II as the ones introduced in the synthetic eIF4E1 R allele .…”