A Novel Motif Mediates the Targeting of theArabidopsis COP1 Protein to Subnuclear Foci*
Abstract
The constitutive photomorphogenesis 1 (COP1) protein of Arabidopsis thaliana accumulates in discrete subnuclear foci. To better understand the role of subnuclear architecture in COP1-mediated gene expression, we investigated the structural motifs of COP1 that mediate its localization to subnuclear foci using mutational analysis with green fluorescent protein as a reporter. In a transient expression assay, a subnuclear localization signal consisting of 58 residues between amino acids 120 and 177 of COP1 was able to confer speckled localization onto the heterologous nuclear NIa protein from tobacco etch virus. The subnuclear localization signal overlaps two previously characterized motifs, a cytoplasmic localization signal and a putative α-helical coiled-coil domain that has been implicated in COP1 dimerization. Moreover, phenotypically lethal mutations in the carboxyl-terminal WD-40 repeats inhibited localization to subnuclear foci, consistent with a functional role for the accumulation of COP1 at subnuclear sites.
Footnotes
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↵* This work was supported by Department of Energy Grant No. DE-FG02-96ER20223.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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↵‡ To whom correspondence should be addressed: Dept. of Botany, The University of Tennessee, Knoxville, TN 37996-1100. Tel.: 423-974-6206; Fax: 423-974-0978; E-mail: vonarnim@utk.edu.
- Abbreviations:
- CLS
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cytoplasmic localization signal
- NLS
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nuclear localization signal
- GFP
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green fluorescent protein
- SNLS
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subnuclear localization signal
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- Received April 20, 1999.
- Revision received July 7, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
