A Novel Ded1-like RNA Helicase Interacts with the Y-box Protein ctYB-1 in Nuclear mRNP Particles and in Polysomes*
- Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, SE-171 77 Stockholm, Sweden
- 4 To whom correspondence should be addressed: Dept. of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, SE-171 77 Stockholm, Sweden. Tel.: 46-8-52487370; Fax: 46-8-313529; E-mail: bertil.daneholt{at}ki.se.
Abstract
We have characterized a novel mRNA-binding protein, designated hrp84, in the dipteran Chironomus tentans and identified it as a DEAD-box RNA helicase. The protein contains the typical helicase core domain, a glycine-rich C-terminal part and a putative nuclear export signal in the N terminus. The protein belongs to the Ded1 subgroup of DEAD-box helicases, which is highly conserved from yeast (Ded1p) to mammals (DDX3). In tissue culture cells, hrp84 is present both in the nucleus and cytoplasm and, as shown by in vivo UV cross-linking, is bound to mRNA in both compartments. Immunoprecipitation experiments revealed that hpr84 is associated with the C. tentans homologue (ctYB-1) of the vertebrate Y-box protein YB-1 both in the nucleus and cytoplasm, and the two proteins also appear together in polysomes. The interaction is likely to be direct as shown by in vitro binding of purified components. We conclude that the mRNA-bound hrp84·ctYB-1 complex is formed in the nucleus and is translocated with mRNA into the cytoplasm and further into polysomes. As both Ded1 and YB-1 are known to regulate the initiation of translation, we propose that the RNA helicase-Y-box protein complex affects the efficiency of mRNA translation, presumably by modulating the conformation of the mRNP template.
Footnotes
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↵5 The abbreviations used are: DEAD-box, protein with Asp-Glu-Ala-Asp motif; PBS, phosphate-buffered saline; eIF, eukaryotic translation initiation factors; hnRNP, heterogenous nuclear ribonucleoproteins.
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↵* The study was supported by the Swedish Research Council, Human Frontier Science Program Organization, and Knut and Alice Wallenberg Foundation. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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The on-line version of this article (available at http://www.jbc.org) contains supplemental figures.
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↵1 Recipient of a fellowship from the Swedish Institute.
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↵2 Recipient of fellowships from the Wenner-Gren Foundations and the Swedish Cancer Fund. Present address: Dept. of Pathology and Oncology, Karolinska University Hospital, SE-17176, Stockholm, Sweden.
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↵3 Present address: Dept. of Molecular Biology and Functional Genomics, Stockholm University, SE-10691 Stockholm, Sweden.
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- Received January 10, 2006.
- Revision received March 17, 2006.
- The American Society for Biochemistry and Molecular Biology, Inc.
