Arabidopsis COP1 protein specifically interacts in vitro with a cytoskeleton-associated protein, CIP1.
Arabidopsis COP1 acts inside the nucleus to suppress photomorphogenic cellular development, and light inactivation of COP1 may involve a specific control of its nuclear activity in hypocotyls and cotyledons, but not in roots, of developing seedlings. To understand the molecular mechanisms of COP1 action during light-mediated development, we initiated a screen for Arabidopsis cDNAs encoding proteins which interact directly with COP1 in vitro as a step to identify the cellular components involved. We report here the isolation and characterization of a cDNA clone encoding a protein designated CIP1 (COP1-interactive protein 1). CIP1 is predominantly alpha-helical and most likely involved in coiled-coil formation. It interacts specifically with the putative coiled-coil region of COP1 in vitro. Further, CIP1 is encoded by a single gene in Arabidopsis, and its mRNA and protein levels are not regulated by light. Immunofluorescent labeling of CIP1 in Arabidopsis seedling protoplasts demonstrated that CIP1 is part of, or associated with, a cytoskeletal structure in hypocotyl and cotyledon cells, but not in roots. Our results are consistent with a possible role of CIP1 in mediating light control of COP1 nuclear activity by regulating its nucleocytoplasmic partitioning.
Matsui
M
M
Department of Biology, Yale University, New Haven, CT 06520-8104, USA.
Stoop
C D
CD
von Arnim
A G
AG
Wei
N
N
Deng
X W
XW
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D018546:Hypocotyl / Q000378:metabolism; D008969:Molecular Sequence Data; D009024:Morphogenesis; D016366:Open Reading Frames; D010940:Plant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D010940:Plant Proteins; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D012097:Repressor Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases