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Published March 3, 2009 | Published + Supplemental Material
Journal Article Open

Structural and functional analysis of the interaction between the nucleoporin Nup214 and the DEAD-box helicase Ddx19


Key steps in the export of mRNA from the nucleus to the cytoplasm are the transport through the nuclear pore complex (NPC) and the subsequent remodeling of messenger RNA-protein (mRNP) complexes that occurs at the cytoplasmic side of the NPC. Crucial for these events is the recruitment of the DEAD-box helicase Ddx19 to the cytoplasmic filaments of the NPC that is mediated by the nucleoporin Nup214. Here, we present the crystal structure of the Nup214 N-terminal domain in complex with Ddx19 in its ADP-bound state at 2.5 Å resolution. Strikingly, the interaction surfaces are not only evolutionarily conserved but also exhibit strongly opposing surface potentials, with the helicase surface being positively and the Nup214 surface being negatively charged. We speculate that the positively charged surface of the interacting ADP-helicase binds competitively to a segment of mRNA of a linearized mRNP, passing through the NPC on its way to the cytoplasm. As a result, the ADP-helicase would dissociate from Nup214 and replace a single bound protein from the mRNA. One cycle of protein replacement would be accompanied, cooperatively, by nucleotide exchange, ATP hydrolysis, release of the ADP-helicase from mRNA and its rebinding to Nup214. Repeat of these cycles would remove proteins from a mRNP, one at a time, akin to a ratchet mechanism for mRNA export.

Additional Information

© 2009 National Academy of Sciences. Contributed by Günter Blobel, December 29, 2008 (sent for review December 9, 2008). We thank Daniel Andor, Martin Kampmann, Vivien Nagy, Alina Patke, Hang Shi, and Pete Stavropoulos for discussions and comments on the manuscript; D. King for mass spectrometry analysis; Stephanie Etherton for help with editing the manuscript; and Corie Ralston and the staff at beamlines 8.2.1 and 8.2.2 of the Advanced Light Source for support during data collection. The peptide array was synthesized by the Protein Center of the Rockefeller University. E.W.D. is a Dale F. and Betty Ann Frey Fellow of the Damon Runyon Cancer Research Foundation. A.H. is supported by a grant from the Leukemia and Lymphoma Society. Author contributions: J.N. and A.H. designed research; J.N., S.A.K., E.W.D., R.W.W., and A.H. performed research; J.N., G.B., and A.H. analyzed data; and J.N., G.B., and A.H. wrote the paper. The authors declare no conflict of interest. Data deposition: The atomic coordinates have been deposited in the Protein Data Bank, www.pdb.org (PDB ID codes 3FMO and 3FMP). This article contains supporting information online at www.pnas.org/cgi/content/full/0813267106/DCSupplemental.

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Published - 3089.full.pdf

Supplemental Material - 0813267106SI.pdf


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