EDF1 coordinates cellular responses to ribosome collisions

Abstract

Translation of aberrant mRNAs induces ribosomal collisions, thereby triggering pathways for mRNA and nascent peptide degradation and ribosomal rescue. Here we use sucrose gradient fractionation combined with quantitative proteomics to systematically identify proteins associated with collided ribosomes. This approach identified Endothelial differentiation-related factor 1 (EDF1) as a novel protein recruited to collided ribosomes during translational distress. Cryo-electron microscopic analyses of EDF1 and its yeast homolog Mbf1 revealed a conserved 40S ribosomal subunit binding site at the mRNA entry channel near the collision interface. EDF1 recruits the translational repressors GIGYF2 and EIF4E2 to collided ribosomes to initiate a negative-feedback loop that prevents new ribosomes from translating defective mRNAs. Further, EDF1 regulates an immediate-early transcriptional response to ribosomal collisions. Our results uncover mechanisms through which EDF1 coordinates multiple responses of the ribosome-mediated quality control pathway and provide novel insights into the intersection of ribosome-mediated quality control with global transcriptional regulation.

Structure of Gcn1 bound to stalled and colliding 80S ribosomes

“…S8a ), a conserved archaeal/eukaryotic protein that suppresses +1 frameshifting at inhibitory CGA-CGA codon pairs in yeast (Wang et al, 2018). Recent findings indicate that the mammalian Mbf1 homolog, EDF1, stabilizes GIGYF2 at collisions to inhibit translation initiation in cis (Juszkiewicz et al, 2020a; Sinha et al, 2020), however, in our reconstruction, we did not observe any additional density for the yeast GIGYF2 homolog. The assignment of Mbf1 was based on (i) the high intensity of Mbf1 peptides in the mass spectrometry analysis of the Gcn1-disome sample (see Dataset S1 ) and (ii) the excellent agreement between the cryo-EM density and a homology model for Mbf1 generated from the NMR structure of the C-terminal helix-turn-helix (HTH) domain of Mbf1 from the fungus Trichoderma reesei (Salinas et al, 2009) ( Fig.…”

Magnesium Deficiency Induces Lipid Accumulation in Vascular Endothelial Cells via Oxidative Stress—The Potential Contribution of EDF-1 and PPARγ

“…In the cytosol, it binds calmodulin [ 11 , 12 , 13 ], a Ca(2+)-binding protein which modulates several calcium-regulated enzymes, among which is the endothelial NO synthase (eNOS) [ 14 ]. In addition, EDF-1 is required for various events associated with ribosome-mediated quality control pathways [ 15 ].…”

Ribosome quality control activity potentiates vaccinia virus protein synthesis during infection

“…Our work indicates that the evolution of a viral response to the host ISR has exposed the virus to a conditional requirement for the RQC pathway in regulating translational reprogramming. While ribosome collisions are part of the regular translation cycle, feedback inhibition of translation initiation through the ISR normally curtails overt RQC activation(Hickey et al 2020; Juszkiewicz et al 2020a; Sinha et al 2020; Vind et al 2020; Wu et al 2020). When viruses interfere with this feedback inhibition, such as vaccinia virus antagonism of PKR-mediated eIF2α phosphorylation, non-productive translation cycles ensue and therefore require RQC based ribosomal rescue.…”

“…Thorough biochemical and genetic studies in multiple organisms have delineated a growing list of molecular constituents within the RQC pathway that act on collided ribosomes(Joazeiro 2019; Inada 2020). Recent studies have uncovered cellular signaling pathways that are induced by collisions that both mount a transcriptional response and result in translation initiation inhibition by multiple routes(Tollenaere et al 2019; Hickey et al 2020; Juszkiewicz et al 2020a; Meydan and Guydosh 2020; Sinha et al 2020; Vind et al 2020; Wu et al 2020). How viruses utilize various RQC components for viral propagation or are impacted by RQC dysfunction remains largely unexplored.…”