title: An Arabidopsis SUMO E3 Ligase, SIZ1, Negatively Regulates Photomorphogenesis by Promoting COP1 Activity.
abstract: COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), a ubiquitin E3 ligase, is a central negative regulator of photomorphogenesis. However, how COP1 activity is regulated by post-translational modifications remains largely unknown. Here we show that SUMO (small ubiquitin-like modifier) modification enhances COP1 activity. Loss-of-function siz1 mutant seedlings exhibit a weak constitutive photomorphogenic phenotype. SIZ1 physically interacts with COP1 and mediates the sumoylation of COP1. A K193R substitution in COP1 blocks its SUMO modification and reduces COP1 activity in vitro and in planta. Consistently, COP1 activity is reduced in siz1 and the level of HY5, a COP1 target protein, is increased in siz1. Sumoylated COP1 may exhibits higher transubiquitination activity than does non-sumoylated COP1, but SIZ1-mediated SUMO modification does not affect COP1 dimerization, COP1-HY5 interaction, and nuclear accumulation of COP1. Interestingly, prolonged light exposure reduces the sumoylation level of COP1, and COP1 mediates the ubiquitination and degradation of SIZ1. These regulatory mechanisms may maintain the homeostasis of COP1 activity, ensuing proper photomorphogenic development in changing light environment. Our genetic and biochemical studies identify a function for SIZ1 in photomorphogenesis and reveal a novel SUMO-regulated ubiquitin ligase, COP1, in plants.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Lin
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: De
authors.initials: D
authors.lastname: Niu
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Zi-Liang
authors.initials: ZL
authors.lastname: Hu
authors.affiliation: Department of Biology, Sunchon National University, Sunchon, Republic of Korea.
authors.forename: Dae Heon
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yin Hua
authors.initials: YH
authors.lastname: Jin
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Cai
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Miura
authors.affiliation: Division of Applied Life Science (BK21Plus), PMBBRC & IALS, Gyeongsang National University, Jinju, Republic of Korea.
authors.forename: Dae-Jin
authors.initials: DJ
authors.lastname: Yun
authors.affiliation: Division of Applied Life Science (BK21Plus), PMBBRC & IALS, Gyeongsang National University, Jinju, Republic of Korea.
authors.forename: Woe-Yeon
authors.initials: WY
authors.lastname: Kim
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Rongcheng
authors.initials: R
authors.lastname: Lin
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jing Bo
authors.identifier: 0000-0001-5847-5138
authors.initials: JB
authors.lastname: Jin
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008025:Ligases / Q000235:genetics* / Q000378:metabolism; D008027:Light; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D063245:Plant Development / Q000235:genetics*; D059748:Proteolysis; D036226:Seedlings / Q000235:genetics / Q000254:growth & development; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism; D058207:Sumoylation / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism; D054875:Ubiquitination / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; C109254:HY5 protein, Arabidopsis; D009687:Nuclear Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C502552:SIZ1 protein, Arabidopsis