Article
- The EMBO Journal (2009) 28, 2293 - 2306
- doi:10.1038/emboj.2009.175
Published online: 25 June 2009
Subject Categories:
Unusual bipartite mode of interaction between the nonsense-mediated decay factors, UPF1 and UPF2
Marcello Clerici1,2, André Mourão3,4,5, Irina Gutsche2, Niels H Gehring6,7, Matthias W Hentze6, Andreas Kulozik6,7, Jan Kadlec1,2, Michael Sattler3,5 and Stephen Cusack1,2
- European Molecular Biology Laboratory, Grenoble Outstation, Grenoble Cedex 9, France
- Unit of Virus Host-Cell Interactions, UJF-EMBL-CNRS, UMI3265, Grenoble Cedex 9, France
- Munich Center for Integrated Protein Science, Department Chemie, Technische Universität München, Garching, Germany
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg, Germany
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and University of Heidelberg, Heidelberg, Germany
- Department of Pediatric Oncology, Hematology and Immunology, Children's Hospital, University of Heidelberg, Heidelberg, Germany
Correspondence to:
Stephen Cusack, Corresponding author. European Molecular Biology Laboratory, Grenoble Outstation, 6 rue Jules Horowitz, BP 181, 38042 Grenoble Cedex 9, France. Tel.: +33 476 207238; Fax: +33 476 207786; E-mail: cusack@embl.fr
Received 1 November 2008; Accepted 3 June 2009
Abstract
Nonsense-mediated decay (NMD) is a eukaryotic quality control mechanism that degrades mRNAs carrying premature stop codons. In mammalian cells, NMD is triggered when UPF2 bound to UPF3 on a downstream exon junction complex interacts with UPF1 bound to a stalled ribosome. We report structural studies on the interaction between the C-terminal region of UPF2 and intact UPF1. Crystal structures, confirmed by EM and SAXS, show that the UPF1 CH-domain is docked onto its helicase domain in a fixed configuration. The C-terminal region of UPF2 is natively unfolded but binds through separated 
-helical and 
-hairpin elements to the UPF1 CH-domain. The -helical region binds sixfold more weakly than the -hairpin, whereas the combined elements bind 80-fold more tightly. Cellular assays show that NMD is severely affected by mutations disrupting the beta-hairpin binding, but not by those only affecting alpha-helix binding. We propose that the bipartite mode of UPF2 binding to UPF1 brings the ribosome and the EJC in close proximity by forming a tight complex after an initial weak encounter with either element.
Keywords:
- mRNA quality control,
- nonsense mediate decay (NMD),
- NMR,
- UPF1,
- UPF2,
- X-ray crystallography
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