Role of eEF2 diphthamide modification in translational fidelity

Diphthamide (DPH) is a conserved amino acid modification on eukaryotic translation elongation factor eEF2. We show that loss of DPH increases -1 ribosomal frameshifting at both programmed, including in SARS-CoV-2, and non-programmed sites. Ribosome profiling of yeast and mammalian cells lacking DPH reveals increased ribosomal drop-off during elongation. The drop-off defect on the long yeast MDN1 gene was suppressed by eliminating out-of-frame stop codons. Our data reveal that loss of DPH impairs the fidelity of translocation during translation elongation resulting in increased rates of ribosomal frameshifting and premature termination at out-of-frame stop codons. Examination of yeast and mammalian cells lacking diphthamide modification in eEF2