title: Arabidopsis COP1 SUPPRESSOR 2 Represses COP1 E3 Ubiquitin Ligase Activity through Their Coiled-Coil Domains Association.
abstract: CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) functions as an E3 ubiquitin ligase and mediates a variety of developmental processes in Arabidopsis by targeting a number of key regulators for ubiquitination and degradation. Here, we identify a novel COP1 interacting protein, COP1 SUPPRESSOR 2 (CSU2). Loss of function mutations in CSU2 suppress the constitutive photomorphogenic phenotype of cop1-6 in darkness. CSU2 directly interacts with COP1 via their coiled-coil domains and is recruited by COP1 into nuclear speckles in living plant cells. Furthermore, CSU2 inhibits COP1 E3 ubiquitin ligase activity in vitro, and represses COP1 mediated turnover of HY5 in cell-free extracts. We propose that in csu2 cop1-6 mutants, the lack of CSU2's repression of COP1 allows the low level of COP1 to exhibit higher activity that is sufficient to prevent accumulation of HY5 in the dark, thus restoring the etiolated phenotype. In addition, CSU2 is required for primary root development under normal light growth condition.
authors.affiliation: State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing, China.|Department of Biological and Environmental Sciences, Gothenburg University, Gothenburg, Sweden.
authors.forename: Dongqing
authors.initials: D
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing, China.|Department of Biological and Environmental Sciences, Gothenburg University, Gothenburg, Sweden.
authors.forename: Yan
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing, China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Ling
authors.affiliation: Department of Chemistry, University of Colombo, Colombo, Sri Lanka.
authors.forename: Chamari
authors.initials: C
authors.lastname: Hettiarachchi
authors.affiliation: Uppsala Genome Center, National Genomics Infrastructure, Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, BMC, Uppsala, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Tellgren-Roth
authors.affiliation: Department of Biological and Environmental Sciences, Gothenburg University, Gothenburg, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Holm
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing, China.
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D001665:Binding Sites; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; C000608770:CSU2 protein, Arabidopsis; C109254:HY5 protein, Arabidopsis; D009687:Nuclear Proteins; D012097:Repressor Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases