Abstract
Establishment of translational competence represents a decisive cytoplasmic step in the biogenesis of 40S ribosomal subunits. This involves final 18S rRNA processing and release of residual biogenesis factors, including the protein kinase RIOK1. To identify novel proteins promoting the final maturation of human 40S subunits, we characterized pre-ribosomal subunits trapped on RIOK1 by mass spectrometry, and identified the deubiquitinase USP16 among the captured factors. We demonstrate that USP16 constitutes a component of late cytoplasmic pre-40S subunits that promotes the removal of ubiquitin from an internal lysine of ribosomal protein RPS27a/eS31. USP16 deletion leads to late 40S subunit maturation defects, manifesting in incomplete processing of 18S rRNA and retarded recycling of late-acting ribosome biogenesis factors, revealing an unexpected contribution of USP16 to the ultimate step of 40S synthesis. Finally, ubiquitination of RPS27a appears to depend on active translation, pointing at a potential connection between 40S maturation and protein synthesis.
Highlights
Ribosomes stand at the center of translation in all kingdoms of life, catalyzing the synthesis of proteins by reading a messenger RNA template
While DIM2 and NOB1 are associated with pre-40S subunits already during earlier nuclear and cytoplasmic 40S subunit maturation steps (Ameismeier et al, 2018; Larburu et al, 2016; Montellese et al, 2017; Wyler et al, 2011; Zemp et al, 2014; Zemp et al, 2009), RIOK1 associates with pre-40S particles only in the course of their final maturation (Ameismeier et al, 2018; Widmann et al, 2012)
Affinity purifications were performed in biological triplicates and the respective eluates were analyzed by mass spectrometry using datadependent acquisition (Supplementary file 2)
Summary
Ribosomes stand at the center of translation in all kingdoms of life, catalyzing the synthesis of proteins by reading a messenger RNA (mRNA) template. While the initial steps of eukaryotic ribosome synthesis leading to the formation of immature preribosomal subunits occur in the nucleolus, ribosomal subunits gain competence for protein translation only during their ultimate maturation in the cytoplasm. This involves structural rearrangements of the subunits, incorporation of late-assembling ribosomal proteins, final ribosomal RNA (rRNA) processing steps, and the eventual release of all ribosome assembly factors (reviewed in Cerezo et al, 2019; Chaker-Margot, 2018; Nerurkar et al, 2015; Pena et al, 2017; Woolford and Baserga, 2013; Zemp and Kutay, 2007).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
