Research Reports:

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Meike Arend1, Koray Ütkür1, Harmen Hawer1, Klaus Mayer2, Namit Ranjan3, Lorenz Adrian4, Ulrich Brinkmann2 and Raffael Schaffrath1

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In yeast, Elongator-dependent tRNA modifications are regulated by the Kti11•Kti13 dimer and hijacked for cell killing by zymocin, a tRNase ribotoxin. Kti11 (alias Dph3) also controls modification of elongation factor 2 (EF2) with diphthamide, the target for lethal ADP-ribosylation by diphtheria toxin (DT). Diphthamide formation on EF2 involves four biosynthetic steps encoded by the DPH1-DPH7 network and an ill-defined KTI13 function. On further examining the latter gene in yeast, we found that kti13Δ null-mutants maintain unmodified EF2 able to escape ADP-ribosylation by DT and to survive EF2 inhibition by sordarin, a diphthamide-dependent antifungal. Consistently, mass spectrometry shows kti13Δ cells are blocked in proper formation of amino-carboxyl-propyl-EF2, the first diphthamide pathway intermediate. Thus, apart from their common function in tRNA modification, both Kti11/Dph3 and Kti13 share roles in the initiation step of EF2 modification. We suggest an alias KTI13/DPH8 nomenclature indicating dual-functionality analogous to KTI11/DPH3.

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ACKNOWLEDGMENTS

We thank Tessa Hübner (MPI, Göttingen, Germany) and Benjamin Scheer (UFZ, Leipzig, Germany) for assistance with EF2 purification and nLC-MS/MS, Dr Roland Klassen (Kassel University, Germany) for critical reading of the manuscript and Prof Jeremy Thorner (University of California, Berkeley, USA) for kindly donating anti-Cdc19 antibodies. The work was supported by DFG (Bonn, Ger-many) Priority Program 1927 Iron-Sulfur for Life to LA (AD178/7-1) and RS (SCHA750/21-1) and by a Diphthamide Pilotgrant to RS (#2887) from ZFF (Kassel University, Germany).

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Yeast gene KTI13 (alias DPH8) operates in the initiation step of diphthamide synthesis on elongation factor 2 by Arend et al. is licensed under a Creative Commons Attribution 4.0 International License.