The COP1–SPA1 interaction defines a critical step in phytochrome A-mediated regulation of HY5 activity
- Yusuke Saijo1,4,
- James A. Sullivan1,4,
- Haiyang Wang2,4,
- Jianping Yang2,
- Yunping Shen1,
- Vicente Rubio1,
- Ligeng Ma1,
- Ute Hoecker3, and
- Xing Wang Deng1,5
- 1 Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA
- 2 Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, New York 14853, USA
- 3 Department of Plant Developmental and Molecular Biology, Institute fur Entwicklungsund Molekularbiologie der Pflanzen, Heinrich-heine-Universitaet, D-40225Duesseldorf, Germany
Abstract
Arabidopsis COP1 is a constitutive repressor of photomorphogenesis that interacts with photomorphogenesis-promoting factors such as HY5 to promote their proteasome-mediated degradation. SPA1 is a repressor of phytochrome A-mediated responses to far-red light. Here we report that COP1 acts as part of a large protein complex and interacts with SPA1 in a light-dependent manner. We further demonstrate the E3 ubiquitin ligase activity of COP1 on HY5 in vitro and the alteration of that activity by SPA1. Thus, the COP1-SPA1 interaction defines a critical step in coordinating COP1-mediated ubiquitination and subsequent degradation of HY5 with PHYA signaling.
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Footnotes
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Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1122903.
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↵4 These authors contributed equally to this work.
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↵5 Corresponding author. E-MAIL xingwang.deng{at}yale.edu; FAX (203) 432-5726.
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- Accepted September 9, 2003.
- Received June 17, 2003.
- Cold Spring Harbor Laboratory Press