The COP1–SPA1 interaction defines a critical step in phytochrome A-mediated regulation of HY5 activity

  1. Yusuke Saijo1,4,
  2. James A. Sullivan1,4,
  3. Haiyang Wang2,4,
  4. Jianping Yang2,
  5. Yunping Shen1,
  6. Vicente Rubio1,
  7. Ligeng Ma1,
  8. Ute Hoecker3, and
  9. Xing Wang Deng1,5
  1. 1 Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA
  2. 2 Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, New York 14853, USA
  3. 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.

Keywords

Footnotes

  • Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1122903.

  • 4 These authors contributed equally to this work.

  • 5 Corresponding author. E-MAIL xingwang.deng{at}yale.edu; FAX (203) 432-5726.

    • Accepted September 9, 2003.
    • Received June 17, 2003.
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