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Structures of B. subtilis Maturation RNases Captured on 50S Ribosome with Pre-rRNAs

2020; Elsevier BV; Volume: 80; Issue: 2 Linguagem: Inglês

10.1016/j.molcel.2020.09.008

1097-4164

Stephanie Oerum, Tom Dendooven, Marjorie Catala, Laetitia Gilet, Clément Dégut, Aude Trinquier, Maxime Bourguet, Pierre Barraud, Sarah Cianférani, Ben F. Luisi, Ciarán Condon, Carine Tisné,

RNA modifications and cancer

The pathways for ribosomal RNA (rRNA) maturation diverge greatly among the domains of life. In the Gram-positive model bacterium, Bacillus subtilis, the final maturation steps of the two large ribosomal subunit (50S) rRNAs, 23S and 5S pre-rRNAs, are catalyzed by the double-strand specific ribonucleases (RNases) Mini-RNase III and RNase M5, respectively. Here we present a protocol that allowed us to solve the 3.0 and 3.1 Å resolution cryoelectron microscopy structures of these RNases poised to cleave their pre-rRNA substrates within the B. subtilis 50S particle. These data provide the first structural insights into rRNA maturation in bacteria by revealing how these RNases recognize and process double-stranded pre-rRNA. Our structures further uncover how specific ribosomal proteins act as chaperones to correctly fold the pre-rRNA substrates and, for Mini-III, anchor the RNase to the ribosome. These r-proteins thereby serve a quality-control function in the process from accurate ribosome assembly to rRNA processing.