Glycobiology Advance Access published online on February 9, 2006
Glycobiology, doi:10.1093/glycob/cwj088
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1 Cell and Molecular Biology Program, Michigan State University, East Lansing, MI 48824, USA
* To whom correspondence should be addressed. Galectin-3, a factor involved in the splicing of pre-mRNA, shuttles between the nucleus and the cytoplasm. We have engineered a vector that expresses the fusion protein containing: (a) Green Fluorescent Protein as a reporter of localization; (b) bacterial maltose-binding protein to increase the size of the reporter polypeptide; and (c) galectin-3, whose sequence we wished to dissect in search of amino acid residues vital for nuclear localization. In mouse 3T3 fibroblasts transfected with this expression construct, the full-length galectin-3 (residues 1-263) fusion protein was localized predominantly in the nucleus. Mutants of this construct, containing truncations of the galectin-3 polypeptide from the amino terminus, retained nuclear localization through residue 128; thus, the amino-terminal half was dispensable for nuclear import. Mutants of the same construct, containing truncations from the carboxyl terminus, showed loss of nuclear localization. This effect was observed beginning with truncation at residue 259, and the full effect was seen with truncation at residue 253. Site-directed mutagenesis of the sequence ITLT (residues 253-256) suggested that nuclear import was dependent on the IXLT type of nuclear localization sequence, first discovered in the Drosophila protein Dsh (dishevelled). In the galectin-3 polypeptide, the activity of this nuclear localization sequence is modulated by a neighboring leucine-rich nuclear export signal.
Received December 7, 2005
Revised January 25, 2006
Accepted February 3, 2006
Article
Transport of Galectin-3 between the Nucleus and Cytoplasm. I. Conditions and Signals for Nuclear Import
Peter J. Davidson 1,
Su-Yin Li 2,
Andrew G. Lohse 3,
Rianna Vandergaast 3,
Elisa Verde 3,
Andrea Pearson 3,
Ronald J. Patterson 4,
John L. Wang 2,
and
Eric J. Arnoys 5 *
2 Departments of Biochemistry, Michigan State University, East Lansing, MI 48824, USA
3 Department of Chemistry and Biochemistry, Calvin College, Grand Rapids, MI 49546, USA
4 Departments of Microbiology, Michigan State University, East Lansing, MI 48824, USA
5 Department of Biochemistry, Michigan State University, East Lansing, MI 48824, USA
Eric J. Arnoys, E-mail: earnoys{at}calvin.edu
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