SRA

Ribosomes undergo substantial conformational changes during translation elongation to accommodate incoming aminoacyl-tRNAs and translocate along the mRNA template. We used multiple elongation inhibitors and chemical probing to define ribosome conformational states corresponding to different sized ribosome-protected mRNA fragments (RPFs) generated by ribosome profiling. We show using various genetic and environmental perturbations that the previously identified 20-22 nucleotide (nt) RPFs correspond predominantly to ribosomes in a pre-accommodation state with an open 40S ribosomal A site while the classical 27-29 nt fragments correspond to ribosomes in a pre-translocation state with an occupied 40S ribosomal A site. These distinct ribosome conformational states revealed by ribosome profiling are seen in all eukaryotes tested including fungi, worms and mammals. This high-resolution ribosome profiling approach reveals the anticipated Rck2-dependent inhibition of translocation through eEF2 phosphorylation during hyperosmotic stress. These same approaches reveal a strong translation elongation arrest during oxidative stress where the ribosomes are trapped in a pre-translocation state, but in this case the translational arrest is independent of Rck2-driven eEF2 phosphorylation. These results provide new insights and approaches for defining the molecular events that impact translation elongation throughout biology. Overall design: 24 biological samples are included for ribosome footprinting samples. These include HeLa, MB-MDA-231 and yeast cells and C. elegans embryos.