PMID:11080276

Citation	Stacey, MG, Kopp, OR, Kim, TH and von Arnim, AG (2000) Modular domain structure of Arabidopsis COP1. Reconstitution of activity by fragment complementation and mutational analysis of a nuclear localization signal in planta. Plant Physiol. 124:979-90
Abstract	The Arabidopsis COP1 protein functions as a developmental regulator, in part by repressing photomorphogenesis in darkness. Using complementation of a cop1 loss-of-function allele with transgenes expressing fusions of cop1 mutant proteins and beta-glucuronidase, it was confirmed that COP1 consists of two modules, an amino terminal module conferring a basal function during development and a carboxyl terminal module conferring repression of photomorphogenesis. The amino-terminal zinc-binding domain of COP1 was indispensable for COP1 function. In contrast, the debilitating effects of site-directed mutations in the single nuclear localization signal of COP1 were partially compensated by high-level transgene expression. The carboxyl-terminal module of COP1, though unable to substantially ameliorate a cop1 loss-of-function allele on its own, was sufficient for conferring a light-quality-dependent hyperetiolation phenotype in the presence of wild-type COP1. Moreover, partial COP1 activity could be reconstituted in vivo from two non-covalently linked, complementary polypeptides that represent the two functional modules of COP1. Evidence is presented for efficient association of the two sub-fragments of the split COP1 protein in Arabidopsis and in a yeast two-hybrid assay.
Links	PubMed PMC59198
Keywords	Arabidopsis/chemistry; Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins; Blotting, Western; Carrier Proteins/chemistry; Carrier Proteins/genetics; Carrier Proteins/metabolism; Genetic Complementation Test; Glucuronidase/genetics; Glucuronidase/metabolism; Light; Mutagenesis, Site-Directed; Nuclear Localization Signals/chemistry; Nuclear Localization Signals/genetics; Nuclear Localization Signals/metabolism; Peptide Fragments/chemistry; Peptide Fragments/metabolism; Phenotype; Plant Proteins/chemistry; Plant Proteins/genetics; Plant Proteins/metabolism; Plant Structures/genetics; Plant Structures/growth & development; Plant Structures/metabolism; Plants, Genetically Modified; Precipitin Tests; Protein Structure, Tertiary; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Repressor Proteins/chemistry; Repressor Proteins/genetics; Repressor Proteins/metabolism; Two-Hybrid System Techniques; Ubiquitin-Protein Ligases
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