Kang D, Wang X, Cao K, Sun C, Deng X W, Wei N
Peking-Yale Joint Center for Plant Molecular Genetics and Agribiotechnology, College of Life Sciences, Peking University, Beijing 100871, China.
Plant J. 2000 Sep;23(5):597-608. doi: 10.1046/j.1365-313x.2000.00824.x.
The COP9 signalosome is a conserved cellular regulator present in diverse organisms. To understand the structural and functional relationship of the COP9 signalosome with its subunits, we expressed in wild-type and mutant Arabidopsis backgrounds two orthologues of subunit 1, rice FUS6 (rFUS6) and human GPS1, and Arabidopsis subunit 8 (COP9). In Arabidopsis, rFUS6 can functionally replace Arabidopsis endogenous FUS6 to form the COP9 signalosome complex and rescue the null fus6-1 mutant phenotype. Moreover, light-grown rFUS6 over-expression seedlings displayed longer hypocotyls and reduced anthocyanin accumulation in comparison to wild-type seedlings, which is opposite to the fus6/cop11 mutant phenotype. The long-hypocotyl phenotype was also observed in transgenic seedlings over-expressing Arabidopsis COP9. This finding indicates that over-expression of a functional subunit 1 or subunit 8 of the COP9 signalosome confers a gain-of-function phenotype relative to the complex. Human GPS1, when expressed in the fus6-1 null mutant of Arabidopsis, can assemble into a chimeric COP9 signalosome at low efficiency, demonstrating the structural conservation of the complexes between human and Arabidopsis. This low-abundancy chimeric complex is insufficient to fully rescue the mutant but is able to attenuate the mutant severity.
COP9信号体是一种存在于多种生物中的保守细胞调节因子。为了了解COP9信号体与其亚基之间的结构和功能关系，我们在野生型和突变拟南芥背景中表达了亚基1的两个直系同源物，即水稻FUS6（rFUS6）和人类GPS1，以及拟南芥亚基8（COP9）。在拟南芥中，rFUS6可以在功能上替代拟南芥内源性FUS6以形成COP9信号体复合物，并挽救fus6-1 null突变体的表型。此外，与野生型幼苗相比，光照下rFUS6过表达的幼苗显示出更长的下胚轴和减少的花青素积累，这与fus6/cop11突变体表型相反。在过表达拟南芥COP9的转基因幼苗中也观察到了长下胚轴表型。这一发现表明，相对于复合物，COP9信号体功能亚基1或亚基8的过表达赋予了功能获得型表型。当在拟南芥的fus6-1 null突变体中表达时，人类GPS1可以低效率组装成嵌合COP9信号体，证明了人类和拟南芥之间复合物的结构保守性。这种低丰度的嵌合复合物不足以完全挽救突变体，但能够减轻突变体的严重程度。
