The RING-Finger E3 Ubiquitin Ligase COP1 SUPPRESSOR1 Negatively Regulates COP1 Abundance in Maintaining COP1 Homeostasis in Dark-Grown Arabidopsis Seedlings.
CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) functions as an E3 ubiquitin ligase in both plants and animals. In dark-grown Arabidopsis thaliana seedlings, COP1 targets photomorphogenesis-promoting factors for degradation to repress photomorphogenesis. Little is known, however, about how COP1 itself is regulated. Here, we identify COP1 SUPPRESSOR1 (CSU1), a RING-finger E3 ubiquitin ligase, as a regulator of COP1. Genetic evidence demonstrates that csu1 mutations suppress cop1-6 phenotypes completely in the dark. Furthermore, CSU1 colocalizes with COP1 in nuclear speckles and negatively regulates COP1 protein accumulation in darkness. CSU1 can ubiquitinate COP1 in vitro and is essential for COP1 ubiquitination in vivo. Therefore, we conclude that CSU1 plays a major role in maintaining COP1 homeostasis by targeting COP1 for ubiquitination and degradation in dark-grown seedlings.
Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden.
Dongqing
D
Xu
Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China.
Fang
F
Lin
Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden.
Yan
Y
Jiang
Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China.
Xi
X
Huang
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Jigang
J
Li
Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China.
Junjie
J
Ling
Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden.
Chamari
C
Hettiarachchi
Uppsala Genome Center, National Genomics Infrastructure-Science for Life Laboratory, Department of Immunology, Genetics, and Pathology, Uppsala University, Rudbeck Laboratory, SE-751 85 Uppsala, Sweden.
Christian
C
Tellgren-Roth
Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden.
Magnus
M
Holm
Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520 xingwang.deng@yale.edu.
Xing Wang
XW
Deng