Department of Molecular Biology and Ecology of Plants, Tel Aviv University, 69978 Ramat Aviv, Israel.
Plant Mol Biol. 2011 Sep;77(1-2):77-89. doi: 10.1007/s11103-011-9795-8. Epub 2011 May 26.
The COP9 Signalosome protein complex (CSN) is a pleiotropic regulator of plant development and contains eight-subunits. Six of these subunits contain the PCI motif which mediates specific protein interactions necessary for the integrity of the complex. COP9 complex subunit 7 (CSN7) contains an N-terminal PCI motif followed by a C-terminal extension which is also necessary for CSN function. A yeast-interaction trap assay identified the small subunit of ribonucelotide reductase (RNR2) from Arabidopsis as interacting with the C-terminal section of CSN7. This interaction was confirmed in planta by both bimolecular fluorescence complementation and immuoprecipitation assays with endogenous proteins. The subcellular localization of RNR2 was primarily nuclear in meristematic regions, and cytoplasmic in adult cells. RNR2 was constitutively nuclear in csn7 mutant seedlings, and was also primarily nuclear in wild type seedlings following exposure to UV-C. These two results correlate with constitutive expression of several DNA-damage response genes in csn7 mutants, and to increased tolerance of csn7 seedlings to UV-C treatment. We propose that the CSN is a negative regulator of RNR activity in Arabidopsis.
COP9 信号体蛋白复合物（CSN）是一种植物发育的多功能调节剂，包含八个亚基。其中六个亚基包含 PCI 基序，介导特定的蛋白质相互作用，对于复合物的完整性是必需的。COP9 复合物亚基 7（CSN7）含有一个 N 端 PCI 基序，其后是一个 C 端延伸，这也是 CSN 功能所必需的。酵母相互作用陷阱测定鉴定出拟南芥的核糖核苷酸还原酶（RNR2）的小亚基与 CSN7 的 C 端部分相互作用。通过体内双分子荧光互补和免疫沉淀测定与内源性蛋白质的相互作用，证实了这一相互作用。RNR2 的亚细胞定位在分生组织区域主要是核内，在成年细胞中主要是细胞质。在 csn7 突变体幼苗中，RNR2 持续核内化，并且在 UV-C 暴露后，在野生型幼苗中也主要是核内化。这两个结果与 csn7 突变体中几种 DNA 损伤反应基因的组成型表达相关，并且与 csn7 幼苗对 UV-C 处理的耐受性增加相关。我们提出 CSN 是拟南芥中 RNR 活性的负调节剂。
