Evidence for functional conservation of a mammalian homologue of the light-responsive plant protein COP1.
Identified in Arabidopsis as a repressor of light-regulated development, the COP1 (constitutively photomorphogenic 1) protein is characterized by a RING-finger motif and a WD40 repeat domain [1]. The subcellular localization of COP1 is light-dependent. COP1 acts within the nucleus to repress photomorphogenic development, but light inactivates COP1 and diminishes its nuclear abundance [2]. Here, we report the identification of a mammalian COP1 homologue that contains all the structural features present in Arabidopsis COP1 (AtCOP1). When expressed in plant cells, a fusion protein comprising mammalian COP1 and beta-glucuronidase (GUS) responded to light by changing its subcellular localization pattern in a manner similar to AtCOP1. Whereas the mammalian COP1 was unable to rescue the defects of Arabidopsis cop1 mutants, expression of the amino-terminal half of mammalian COP1 in Arabidopsis interfered with endogenous COP1 function, resulting in a hyperphotomorphogenic phenotype. Therefore, the regulatory modules in COP1 proteins that are responsible for the signal-dependent subcellular localization are functionally conserved between higher plants and mammals, suggesting that mammalian COP1 may share a common mode of action with its plant counterpart in regulating development and cellular signaling.
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA.
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D000818:Animals; D017360:Arabidopsis / Q000737:chemistry* / Q000254:growth & development; D029681:Arabidopsis Proteins; D002352:Carrier Proteins / Q000737:chemistry* / Q000502:physiology; D002478:Cells, Cultured; D005966:Glucuronidase / Q000032:analysis; D006801:Humans; D008027:Light; D019697:Onions; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry* / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000502:physiology; D044767:Ubiquitin-Protein Ligases
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D005966:Glucuronidase