Backbone resonance assignments of the C-terminal region of human translation initiation factor eIF4B

Abstract

Translation initiation in eukaryotes is an early step in protein synthesis, requiring multiple factors to recruit the ribosomal small subunit to the mRNA 5' untranslated region. One such protein factor is the eukaryotic translation initiation factor 4B (eIF4B), which increases the activity of the eIF4A RNA helicase, and is linked to cell survival and proliferation. We report here the protein backbone chemical shift assignments corresponding to the C-terminal 279 residues of human eIF4B. Analysis of the chemical shift values identi es one main helical region in the area previously linked to RNA binding, and con rms that the overall C-terminal region is intrinsically disordered. Biological contextAt its core, translation initiation in eukaryotes involves recruitment of the small ribosomal subunit with associated protein factors (the 43S pre-initiation complex) onto the protein-coding mRNA (Jackson et al. 2010). This process is usually achieved by the help of a mRNA cap-binding complex known as eukaryotic translation initiation factor 4F (eIF4F; comprising the three factors eIF4E, eIF4A and eIF4G), as well as eIF4B (or the homologue eIF4H) (Merrick 2015). In a concerted action, these factors recognize the mRNA 5'-cap and unwind the structured elements at the 5'-end untranslated region (5'-UTR) of the mRNA. This action facilitates the recruitment of the 43S pre-initiation complex, the scanning of the mRNA towards the start-codon recognition, and also ribosome assembly (Jackson et al. 2010). Throughout this process,

Disordered regions of human eIF4B orchestrate a dynamic self-association landscape

“…To return to the DRYG-CTR construct at moderate ionic strength, the number and position of observed amide crosspeaks is remarkably similar to the pattern observed for the isolated CTR 29 . An overlay of the DRYG-CTR and CTR spectra at 150 mM NaCl highlights this similarity (Fig.…”

“…The CD spectrum shows a large minimum at 202 nm and small ellipticity signal at 220 nm, which is consistent with low secondary structure content as expected for disordered proteins. The small contribution of ellipticity at 220 nm is likely originating from transient short helical motifs at the CTR suggested by our previous NMR data 29 (Supplementary Fig. 1).…”

“…Recently, we have also characterized the atomic details of the C-terminal region (CTR) of eIF4B, encompassing residues 333 to 611, and experimentally confirmed that this region is indeed highly intrinsically disordered 29 . Nonetheless, we could also identify a short helical segment that coincides with the previously mapped arginine-rich motif (ARM) implicated in RNA binding 11,30 (Fig.…”

“…Samples contained 170 μL in a 3mm NMR tube at 293 K, in a buffer containing 20 mM NaP (pH 7.0), 2 mM DTT, and varying amounts of NaCl and GdmCl (deuterated). Chemical shift assignments for eIF4B-CTR were previously deposited in the BMRB (https://bmrb.io/) under accession codes 51952, 51953 and 51957 29 .…”