The Nuclear Localization Signal of Lymphoid Enhancer Factor-1 Is Recognized by Two Differentially Expressed Srp1-Nuclear Localization Sequence Receptor Proteins (*)
- From the Department of Microbiology and Molecular Genetics, University of California, Irvine, California 92717-4025
- §To whom correspondence and reprint requests should be addressed. Tel.: 714-824-2885; Fax: 714-824-8598.
Abstract
Proteins are directed to the nucleus by their nuclear localization sequences (NLSs) in a multistep process. The first step, which is to dock the NLS-containing protein to the nuclear pore, is carried out in part by a recently identified NLS receptor named Srp1/importin-α. Using the high mobility group (HMG) DNA binding domain of human lymphoid enhancer factor-1 (hLEF-1) as bait in a yeast two-hybrid screen, we have identified two different mouse Srp1 proteins (pendulin/importin-α and mSrp1) that each bind to a 9-amino acid sequence in hLEF-1 called the B box. We show that the B box of hLEF-1, a region essential for high affinity DNA binding, is also necessary and sufficient for nuclear localization, lending support to the model that NLSs can function both in nuclear transport and DNA binding. Pendulin and mSrp1 are the mouse homologues of hRch1/hSrp1α/importin-α and hSrp1/karyopherin α/NPI-1, respectively, and show considerable sequence divergence from each other. We find a surprising and significant difference in the expression pattern of pendulin and mSrp1 mRNA, suggesting that these two Srp1 proteins are distinguishable in function as well as sequence.
Footnotes
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↵* This work was supported by National Institutes of Health Grant CA-62079 and in part by support from the University of California (Irvine) Academic Senate Committee on Research and a Leukemia Society Special Fellowship (to M. L. W.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank(™)/EMBL Data Bank with accession number(s) U34228 and U34229.
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↵1 The abbreviations used are:
- NLS
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nuclear localization signal
- HMG
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high mobility group
- hLEF-1
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human lymphoid enhancer factor-1
- hTCF-1
-
human T cell factor-1
- GST
-
glutathione S-transferase
- PAGE
-
polyacrylamide gel electrophoresis
- PBS
-
phosphate-buffered saline
- BSA
-
bovine serum albumin
- FITC
-
fluorescein isothiocyanate
- GFP
-
green fluorescent protein.
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↵2T. Loftus and E. Stanbridge, unpublished results.
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↵3J. A. Claypool and S. Sandmeyer, unpublished results.
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- Received November 28, 1995.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
