Human Ribosomal Protein L5 Contains Defined Nuclear Localization and Export Signals*
- Olaf Rosorius‡§,
- Barbara Fries‡§,
- Roland H. Stauber‡§,
- Nicole Hirschmann‡,
- Dorian Bevec¶‖ and
- Joachim Hauber‡**
- From the ‡Institute for Clinical and Molecular Virology, University Erlangen-Nürnberg, Schloßgarten 4, D-91054 Erlangen, Germany and the ¶Novartis Research Institute, Department of Immunology, Brunner Straße 59, A-1235 Vienna, Austria
Abstract
Ribosomal protein L5 is part of the 60 S ribosomal subunit and localizes in both the cytoplasm and the nucleus of eukaryotic cells, accumulating particularly in the nucleoli. L5 is known to bind specifically to 5 S rRNA and is involved in nucleocytoplasmic transport of this rRNA. Here, we report a detailed analysis of the domain organization of the human ribosomal protein L5. We show that a signal that mediates nuclear import and nucleolar localization maps to amino acids 21–37 within the 297-amino acid L5 protein. Furthermore, carboxyl-terminal residues at positions 255–297 serve as an additional nuclear/nucleolar targeting signal. Domains involved in 5 S rRNA binding are located at both the amino terminus and the carboxyl terminus of L5. Microinjection studies in somatic cells demonstrate that a nuclear export signal (NES) that maps to amino acids 101–111 resides in the central region of L5. This NES is characterized by a pronounced clustering of critical leucine residues, which creates a peptide motif not previously observed in other leucine-rich NESs. Finally, we present a refined model of the multidomain structure of human ribosomal protein L5.
Footnotes
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↵* This work was supported by Deutsche Forschungsgemeinschaft Grant SFB466.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.
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↵§ These authors contributed equally to this work.
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↵‖ Current address: Axxima Pharmaceuticals AG, Am Klopferspitz 19, D-82152 Martinsried, Germany
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↵** To whom correspondence should be addressed. Tel.: 49-9131-85-26182; Fax: 49-9131-85-22101; E-mail: jmhauber@viro.med.uni- erlangen.de.
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↵2 O. Rosorius, unpublished data.
- Abbreviations:
- HIV-1
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human immunodeficiency virus type 1
- GFP
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green fluorescent protein
- GST
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glutathione S-transferase
- βGal
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β-galactosidase
- NLS
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nuclear localization signal
- NES
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nuclear export signal
- aa
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amino acid(s)
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- Received October 22, 1999.
- Revision received January 7, 2000.
- The American Society for Biochemistry and Molecular Biology, Inc.
