The Bowen–Conradi syndrome protein Nep1 (Emg1) has a dual role in eukaryotic ribosome biogenesis, as an essential assembly factor and in the methylation of Psi1191 in yeast 18S rRNA

  • The Nep1 (Emg1) SPOUT-class methyltransferase is an essential ribosome assembly factor and the human Bowen–Conradi syndrome (BCS) is caused by a specific Nep1D86G mutation. We recently showed in vitro that Methanocaldococcus jannaschii Nep1 is a sequence-specific pseudouridine-N1-methyltransferase. Here, we show that in yeast the in vivo target site for Nep1-catalyzed methylation is located within loop 35 of the 18S rRNA that contains the unique hypermodification of U1191 to 1-methyl-3-(3-amino-3-carboxypropyl)-pseudouri-dine (m1acp3Psi). Specific 14C-methionine labelling of 18S rRNA in yeast mutants showed that Nep1 is not required for acp-modification but suggested a function in Psi1191 methylation. ESI MS analysis of acp-modified Psi-nucleosides in a DeltaNep1-mutant showed that Nep1 catalyzes the Psi1191 methylation in vivo. Remarkably, the restored growth of a nep1-1ts mutant upon addition of S-adenosylmethionine was even observed after preventing U1191 methylation in a deltasnr35 mutant. This strongly suggests a dual Nep1 function, as Psi1191-methyltransferase and ribosome assembly factor. Interestingly, the Nep1 methyltransferase activity is not affected upon introduction of the BCS mutation. Instead, the mutated protein shows enhanced dimerization propensity and increased affinity for its RNA-target in vitro. Furthermore, the BCS mutation prevents nucleolar accumulation of Nep1, which could be the reason for reduced growth in yeast and the Bowen-Conradi syndrome.

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Author:Britta Meyer, Jan Philip WurmGND, Peter KötterORCiD, Matthias LeisegangORCiDGND, Valeska Schilling, Markus BuchhauptORCiDGND, Martin Held, Ute Bahr, Michael KarasGND, Alexander HeckelORCiDGND, Markus Bohnsack, Jens WöhnertORCiDGND, Karl-Dieter Entian
Pubmed Id:
Parent Title (English):Nucleic acids research
Publisher:Oxford Univ. Press
Place of publication:Oxford
Document Type:Article
Date of Publication (online):2010/10/23
Date of first Publication:2010/10/23
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2010/11/12
Page Number:12
First Page:1526
Last Page:1537
© The Author(s) 2010. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Institutes:Biowissenschaften / Biowissenschaften
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Sammlung Biologie / Sondersammelgebiets-Volltexte
Licence (German):License LogoCreative Commons - Namensnennung-Nicht kommerziell 2.0