Peng Z, Serino G, Deng X W
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520-8104, USA.
Development. 2001 Nov;128(21):4277-88. doi: 10.1242/dev.128.21.4277.
The COP9 signalosome is a highly conserved eight-subunit protein complex initially defined as a repressor of photomorphogenic development in Arabidopsis. It has recently been suggested that the COP9 signalosome directly interacts and regulates SCF type E3 ligases, implying a key role in ubiquitin-proteasome mediated protein degradation. We report that Arabidopsis FUS11 gene encodes the subunit 3 of the COP9 signalosome (CSN3). The fus11 mutant is defective in the COP9 signalosome and accumulates significant amount of multi-ubiquitinated proteins. The same mutant is specifically impaired in the 26S proteasome-mediated degradation of HY5 but not PHYA, indicating a selective involvement in protein degradation. Reduction-of-function transgenic lines of CSN3 produced through gene co-suppression also accumulate multi-ubiquitinated proteins and exhibit diverse developmental defects. This result substantiates a hypothesis that the COP9 signalosome is involved in multifaceted developmental processes through regulating proteasome-mediated protein degradation.
COP9信号体是一种高度保守的八亚基蛋白质复合物，最初被定义为拟南芥中光形态建成发育的抑制因子。最近有人提出，COP9信号体直接与SCF型E3连接酶相互作用并对其进行调控，这意味着它在泛素-蛋白酶体介导的蛋白质降解中起关键作用。我们报道，拟南芥FUS11基因编码COP9信号体的亚基3（CSN3）。fus11突变体在COP9信号体中存在缺陷，积累了大量多泛素化蛋白。同一突变体在26S蛋白酶体介导的HY5降解中受到特异性损害，但在PHYA降解中未受影响，表明其选择性参与蛋白质降解。通过基因共抑制产生的CSN3功能降低转基因系也积累多泛素化蛋白，并表现出多种发育缺陷。这一结果证实了一个假说，即COP9信号体通过调节蛋白酶体介导的蛋白质降解参与多方面的发育过程。
