Disease relevance of EIF5

• Binding analysis with human eIF2beta deletion mutants expressed in Escherichia coli identified a 22-amino acid domain, between amino acids 68 and 89, as the primary eIF5-binding region of eIF2beta [1].

High impact information on EIF5

• Here we show that hydrolysis of eIF2-bound GTP induced by eIF5 in 48S complexes is necessary but not sufficient for the subunits to join [2].
• In the absence of eIF1, eIF5-stimulated hydrolysis of eIF2-bound GTP occurred at the same rate in 43S pre-initiation and 48S initiation complexes [3].
• Interestingly, the 131,133 CTT mutation enhances initiation at UUG codons (Sui(-) phenotype) and decreases leaky scanning at AUG, while the NTT mutation 17-21 suppresses the Sui(-) phenotypes of eIF5 and eIF2beta mutations and increases leaky scanning [4].
• An eIF5/eIF2 complex antagonizes guanine nucleotide exchange by eIF2B during translation initiation [5].
• CK2 phosphorylation of eukaryotic translation initiation factor 5 potentiates cell cycle progression [6].

Biological context of EIF5

• This interaction is essential for eIF5-promoted hydrolysis of GTP bound to the 40 S initiation complex [7].
• Additionally, alanine substitution mutagenesis of eIF5 defined Lys-33 and Lys-55 as also critical for eIF5 function in vitro and in vivo [7].
• Using MS, we show that Ser-389 and -390 of eIF5 are major sites of phosphorylation by CK2 [6].
• Expression of these mutants reveals that they have a dominant-negative effect on phosphorylation of endogenous eIF5, and that they perturb synchronous progression of cells through S to M phase, resulting in a significant reduction in growth rate [6].
• Additionally, we demonstrate tissue-specific variations in eIF-5 mRNA expression as well as preference for polyadenylation sites [8].

Anatomical context of EIF5

• Joining of 48S complexes to 60S subunits to form 80S ribosomes requires eIF5B, which has an essential ribosome-dependent GTPase activity and hydrolysis of eIF2-bound GTP induced by eIF5 [9].
• These findings suggest that eIF5-eIF2beta interaction plays an essential role in eIF5 function in eukaryotic cells [10].
• We isolated a protein kinase from rabbit reticulocyte lysates on the basis of its ability to phosphorylate purified bacterially expressed recombinant rat eIF5 [11].

Associations of EIF5 with chemical compounds

• Mutation of this arginine residue to alanine or even to conservative lysine caused a severe defect in the ability of eIF5 to promote GTP hydrolysis from the 40 S initiation complex, although the ability of these mutant proteins to bind to eIF2 beta remained unchanged [7].
• Alanine substitution mutagenesis at sites within this region defined several conserved glutamic acid residues in a bipartite motif as critical for eIF5 function [10].
• Thus, rather than allosterically regulating eIF2gamma-G domain function via eIF2beta, our data support a model in which the GTPase-activating factor eIF5 and the guanine-nucleotide exchange factor eIF2B modulate eIF2 function through direct interactions with the eIF2gamma-G domain [12].
• Direct Binding of Translation Initiation Factor eIF2{gamma}-G Domain to Its GTPase-activating and GDP-GTP Exchange Factors eIF5 and eIF2B{epsilon} [12].
• These serine residues are embedded within a cluster of acidic amino acid residues and account for nearly 90% of the total in vitro eIF5 phosphorylation [11].

Other interactions of EIF5

• We have determined the crystal structure of residues 544-704 from yeast eIF2Bepsilon at 2.3-A resolution, and this fragment is an all-helical protein built around the conserved aromatic acidic (AA) boxes also found in eIF4G and eIF5 [13].
• Here, we report the quantitative characterization of energetic interactions between eIF1A, eIF5 and the AUG codon in an in vitro reconstituted yeast translation initiation system [14].

Analytical, diagnostic and therapeutic context of EIF5

• The accumulation of eIF-5 mRNA was studied by RNA blot and in situ hybridization [15].

References