The cryo-EM structure of a ribosome–Ski2-Ski3-Ski8 helicase complex

Christian Schmidt (1) , Eva Kowalinski (2) , Vivekanandan Shanmuganathan (1) , Quentin Defenouillère (3, 4) , Katharina Braunger (1) , André Heuer (1) , Markus Pech (1) , Abdelkader Namane (3) , Otto Berninghausen (1) , Micheline Fromont-Racine (3) , Alain Jacquier (3) , Elena Conti (2) , Thomas Becker (1) , Roland Beckmann (1)

1 CIPSM - Center for Integrated Protein Science
2 MPIB - Max-Planck-Institut für Biochemie = Max Planck Institute of Biochemistry
3 Génétique des Interactions macromoléculaires / Genetics of Macromolecular Interactions
4 ED 515 - Complexité du vivant

Ski2-Ski3-Ski8 (Ski) is a helicase complex functioning with the RNA-degrading exosome to mediate the 3'-5' messenger RNA (mRNA) decay in turnover and quality-control pathways. We report that the Ski complex directly associates with 80S ribosomes presenting a short mRNA 3' overhang. We determined the structure of an endogenous ribosome-Ski complex using cryo-electron microscopy (EM) with a local resolution of the Ski complex ranging from 4 angstroms (Å) in the core to about 10 Å for intrinsically flexible regions. Ribosome binding displaces the autoinhibitory domain of the Ski2 helicase, positioning it in an open conformation near the ribosomal mRNA entry tunnel. We observe that the mRNA 3' overhang is threaded directly from the small ribosomal subunit to the helicase channel of Ski2, primed for ongoing exosome-mediated 3'-5' degradation.

Domaines: Sciences du Vivant [q-bio]

Christian Schmidt, Eva Kowalinski, Vivekanandan Shanmuganathan, Quentin Defenouillère, Katharina Braunger, et al.. The cryo-EM structure of a ribosome–Ski2-Ski3-Ski8 helicase complex. Science, 2016, 354 (6318), pp.1431-1433. ⟨10.1126/science.aaf7520⟩. ⟨pasteur-03431216⟩