Functional dissection of Arabidopsis COP1 reveals specific roles of its three structural modules in light control of seedling development.
Arabidopsis COP1 acts as a repressor of photomorphogenesis in darkness, and light stimuli abrogate the repressive ability and nuclear abundance of COP1. COP1 has three known structural modules: an N-terminal RING-finger, followed by a predicted coiled-coil and C-terminal WD-40 repeats. A systematic study was undertaken to dissect the functional roles of these three COP1 domains in light control of Arabidopsis seedling development. Our data suggest that COP1 acts primarily as a homodimer, and probably dimerizes through the coiled-coil domain. The RING-finger and the coiled-coil domains can function independently as light-responsive modules mediating the light-controlled nucleocytoplasmic partitioning of COP1. The C-terminal WD-40 domain functions as an autonomous repressor module since the overexpression of COP1 mutant proteins with intact WD-40 repeats are able to suppress photomorphogenic development. This WD-40 domain-mediated repression can be at least in part accounted for by COP1's direct interaction with and negative regulation of HY5, a bZIP transcription factor that positively regulates photomorphogenesis. However, COP1 self-association is a prerequisite for the observed interaction of the COP1 WD-40 repeats with HY5. This work thus provides a structural basis of COP1 as a molecular switch.
Torii
K U
KU
Department of Molecular, Cellular and Developmental Biology, Yale University, PO Box 208104, 165 Prospect Street, OML 301, New Haven, CT 06520-8104, USA.
McNellis
T W
TW
Deng
X W
XW
D017360:Arabidopsis / Q000254:growth & development* / Q000528:radiation effects*; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D019281:Dimerization; D018546:Hypocotyl / Q000254:growth & development / Q000528:radiation effects; D008027:Light; D009024:Morphogenesis; D009687:Nuclear Proteins / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins; C109254:HY5 protein, Arabidopsis; D009687:Nuclear Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases