We are interested in the cellular signaling process responsible for regulation of development by extracellular stimuli. We used two model systems: the light control of Arabidopsis seedling development and a conserved cellular pathway in mammals. During our dissection of the genetic network involved in light control of Arabidopsis development, eleven pleiotropic COP/DET/FUS loci have been identified and revealed to be responsible for mediating light control of Arabidopsis seedling developmental program switch. Among them, COP1 is the master repressor of photomorphogenic development and acts within the nucleus as an E3 ligase by directly targeting photomorphogenesis-promoting transcription factors1 degradation by the 26S proteasome in darkness. Light inactivates COP1 and causes a reduction in its nuclear abundance. Another gene, COP10, encodes a likely E2 component. Most remaining genes encode subunits of a highly conserved multi-subunit protein complex, the COP9 signalosome, which defines a novel regulator of the E3 ligases and promotes de-conjugation of NEDD8/RUB1 from the certain E3 ligase. Therefore this group of regulators define new cellular machinery in regulating cellular responses to external stimuli or stresses. Currently, we are applying both molecular genetics and genomic approaches to further analyze this novel cellular machinery conserved among all multicellular organisms. We wish to understand signaling mechanisms in how extracellular signals regulate this machinery pathway and how this machinery controls the genome expression pattern in response to the environmental signals.
Sullivan JA, Shirasu K, Deng XW. (2003). The diverse roles of ubiquitin and the 26S proteasome in the life of plants. Nat Rev Genet. Dec;4(12):948-58
Saijo Y, Sullivan JA, Wang H, Yang J, Shen Y, Rubio V, Ma L, Hoecker U, Deng XW. (2003). The COP1-SPA1 interaction defines a critical step in phytochrome A-mediated regulation of HY5 activity. Genes Dev. 2003 Nov 1;17(21):2642-7.
Suzuki, G., Yanagawa, Y., Kwok, S.F., Matsui, M., and Deng, X.W. (2002). Arabidopsis COP10 is an ubiquitin-conjugating enzyme variant that acts together with COP1 and the COP9 signalosome in repressing photomorphogenesis. Genes & Dev. 16:554-559.
Wang, H., Ma, L.G., Li, J.M., Zhao, H.Y., and Deng, X.W. (2001). Direct interaction of Arabidopsis cryptochromes with COP1 in light control development. Science 294:154-158. (epublication and news on 16th August).
Schwechheimer, C., et. al. (2001). The COP9 signalosome associates with SCFTIR1 ubiquitin ligase and plays a critical role for SCFTIR1-mediated auxin responses. Science 292:1379-1382.
See also Dept. MCDB Yale Universtity