The Glucocorticoid Receptor Is Associated with the RNA-binding Nuclear Matrix Protein hnRNP U*
- Martin Eggert,
- Jörg Michel,
- Sandra Schneider,
- Harald Bornfleth‡,
- Aria Baniahmad,
- Frank O. Fackelmayer§,
- Susanne Schmidt and
- Rainer Renkawitz¶
- From the Genetisches Institut der Justus-Liebig-Universität, Heinrich-Buff-Ring 58–62, D-35392, the ‡Institut für Angewandte Physik, Ruprecht-Karls-Universität, Albert-Ueberle-Strasse 3–5, D-69120 Heidelberg, and the§Fakultät für Biologie der Universität, Universitätsstrasse 10, D-78646 Konstanz, Germany
Abstract
The glucocorticoid receptor (GR) is a ligand-dependent transcription factor that is able to modulate gene activity by binding to its response element, interacting with other transcription factors, and contacting several accessory proteins such as coactivators. Here we show that GRIP120, one of the factors we have identified to interact with the glucocorticoid receptor, is identical to the heterogeneous nuclear ribonucleoprotein U (hnRNP U), a nuclear matrix protein binding to RNA as well as to scaffold attachment regions. GR·hnRNP U complexes were identified by blotting and coimmunoprecipitation. The subnuclear distribution of GR and hnRNP U was characterized by indirect immunofluorescent labeling and confocal laser microscopy demonstrating a colocalization of both proteins. Using a nuclear transport-deficient deletion of hnRNP U, nuclear translocation was seen to be dependent on GR and dexamethasone. Transient transfections were used to identify possible interaction domains. Overexpressed hnRNP U interfered with glucocorticoid induction, and the COOH-terminal domains of both proteins were sufficient in mediating the transcriptional interference. A possible functional role for this GR binding-protein in addition to its binding to the nuclear matrix, to RNA, and to scaffold attachment regions is discussed.
Footnotes
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↵* This work was supported in part by Deutsche Forschungsgemeinschaft Grant Re 433/9-3) and by the Fonds der Chemischen Industrie.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The first two authors contributed equally to this manuscript, which is part of the Ph.D. thesis of J. M.
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↵‡ Supported by a fellowship from the Studienstiftung des Deutschen Volkes.
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↵¶ To whom correspondence should be addressed. Tel.: 641-99-35460; Fax: 641-99-35469; E-mail:Rainer.Renkawitz{at}gen.bio.uni-giessen.de.
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↵1 The abbreviations used are: hnRNP U, heterogeneous nuclear ribonucleoprotein U; GR, glucocorticoid receptor; CAT, chloramphenicol acetyltransferase; PAGE, polyacrylamide gel electrophoresis; PBS, phosphate-buffered saline; GRIP, GR-interacting protein; HPLC, high performance liquid chromatography; FITC, fluorescein isothiocyanate; TRITC, tetramethylrhodamine isothiocyanate; hGR, human glucocorticoid receptor; tk, thymidine kinase; GRE, glucocorticoid-responsive element; NLS, nuclear localization signal; DBD, DNA binding domain.
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↵2 F. O. Fackelmayer, unpublished data.
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↵3 S. Schneider, unpublished data.
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- Received July 16, 1997.
