The association of late-acting snoRNPs with human pre-ribosomal complexes requires the RNA helicase DDX21

Nucleic Acids Res. 2015 Jan;43(1):553-64. doi: 10.1093/nar/gku1291.

Katherine E Sloan ¹, Matthias S Leisegang ², Carmen Doebele ¹, Ana S Ramírez ², Stefan Simm ³, Charlotta Safferthal ³, Jens Kretschmer ¹, Tobias Schorge ⁴, Stavroula Markoutsa ⁴, Sara Haag ¹, Michael Karas ⁴, Ingo Ebersberger ⁵, Enrico Schleiff ⁶, Nicholas J Watkins ⁷, Markus T Bohnsack ⁸

Affiliations

1 Institute for Molecular Biology, Göttingen University Medical Department, 37073 Göttingen, Germany.
2 Institute for Molecular Biology, Göttingen University Medical Department, 37073 Göttingen, Germany Institute for Molecular Biosciences, Goethe University, 60438 Frankfurt, Germany.
3 Institute for Molecular Biosciences, Goethe University, 60438 Frankfurt, Germany.
4 Institute of Pharmaceutical Chemistry, Goethe University, 60438 Frankfurt, Germany.
5 Institute for Cell Biology and Neuroscience, Goethe University, 60438 Frankfurt, Germany.
6 Institute for Molecular Biosciences, Goethe University, 60438 Frankfurt, Germany Cluster of Excellence Macromolecular Complexes, Goethe University, 60438 Frankfurt, Germany.
7 Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
8 Institute for Molecular Biology, Göttingen University Medical Department, 37073 Göttingen, Germany Institute for Molecular Biosciences, Goethe University, 60438 Frankfurt, Germany Cluster of Excellence Macromolecular Complexes, Goethe University, 60438 Frankfurt, Germany Göttingen Centre for Molecular Biosciences, Georg-August-University, 37073 Göttingen, Germany Markus.Bohnsack@med.uni-goettingen.de.

PMID: 25477391 DOI: 10.1093/nar/gku1291

Abstract

Translation fidelity and efficiency require multiple ribosomal (r)RNA modifications that are mostly mediated by small nucleolar (sno)RNPs during ribosome production. Overlapping basepairing of snoRNAs with pre-rRNAs often necessitates sequential and efficient association and dissociation of the snoRNPs, however, how such hierarchy is established has remained unknown so far. Here, we identify several late-acting snoRNAs that bind pre-40S particles in human cells and show that their association and function in pre-40S complexes is regulated by the RNA helicase DDX21. We map DDX21 crosslinking sites on pre-rRNAs and show their overlap with the basepairing sites of the affected snoRNAs. While DDX21 activity is required for recruitment of the late-acting snoRNAs SNORD56 and SNORD68, earlier snoRNAs are not affected by DDX21 depletion. Together, these observations provide an understanding of the timing and ordered hierarchy of snoRNP action in pre-40S maturation and reveal a novel mode of regulation of snoRNP function by an RNA helicase in human cells.

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