title: Noncanonical role ofArabidopsisCOP1/SPA complex in repressing BIN2-mediated PIF3 phosphorylation and degradation in darkness.
abstract: The E3 ligase CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) has been known to mediate key signaling factors for degradation via the ubiquitin/26S proteasome pathway in both plants and animals. Here, we report a noncanonical function ofArabidopsisCOP1, the central repressor of photomorphogenesis, in the form of a COP1/ SUPPRESSOR ofphyA-105(SPA) complex. We show that the COP1/SPA complex associates with and stabilizes PHYTOCHROME INTERACTING FACTOR 3 (PIF3) to repress photomorphogenesis in the dark. We identify the GSK3-like kinase BRASSINOSTEROID-INSENSITIVE 2 (BIN2) as a kinase of PIF3, which induces PIF3 degradation via 26S proteasome during skotomorphogenesis. Mutations on two typical BIN2 phosphorylation motifs of PIF3 lead to a strong stabilization of the protein in the dark. We further show that the COP1/SPA complex promotes PIF3 stability by repressing BIN2 activity. Intriguingly, without affecting BIN2 expression, the COP1/SPA complex modulates BIN2 activity through interfering with BIN2-PIF3 interaction, thereby inhibiting BIN2-mediated PIF3 phosphorylation and degradation. Taken together, our results suggest another paradigm for COP1/SPA complex action in the precise control of skotomorphogenesis.
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 100871, China.
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Ling
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 100871, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
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 100871, China zhudanmeng@pku.edu.cn deng@pku.edu.cn.
authors.forename: Danmeng
authors.initials: D
authors.lastname: Zhu
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 100871, China zhudanmeng@pku.edu.cn deng@pku.edu.cn.
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D010766:Phosphorylation / Q000528:radiation effects; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis / Q000528:radiation effects; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D011494:Protein Kinases; D044767:Ubiquitin-Protein Ligases; C116162:PIF3 protein, Arabidopsis; C118571:SPA1 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis; C448985:At4g18710 protein, Arabidopsis
keywords: COP1/SPA complex; photomorphogenesis; posttranscriptional regulation