Book Adam J, Smalle Jan, Lee Kwang-Hee, Yang Peizhen, Walker Joseph M, Casper Sarah, Holmes James H, Russo Laura A, Buzzinotti Zachri W, Jenik Pablo D, Vierstra Richard D
Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA.
Plant Cell. 2009 Feb;21(2):460-78. doi: 10.1105/tpc.108.064444. Epub 2009 Feb 27.
The 26S proteasome is an essential multicatalytic protease complex that degrades a wide range of intracellular proteins, especially those modified with ubiquitin. Arabidopsis thaliana and other plants use pairs of genes to encode most of the core subunits, with both of the isoforms often incorporated into the mature complex. Here, we show that the gene pair encoding the regulatory particle non-ATPase subunit (RPN5) has a unique role in proteasome function and Arabidopsis development. Homozygous rpn5a rpn5b mutants could not be generated due to a defect in male gametogenesis. While single rpn5b mutants appear wild-type, single rpn5a mutants display a host of morphogenic defects, including abnormal embryogenesis, partially deetiolated development in the dark, a severely dwarfed phenotype when grown in the light, and infertility. Proteasome complexes missing RPN5a are less stable in vitro, suggesting that some of the rpn5a defects are caused by altered complex integrity. The rpn5a phenotype could be rescued by expression of either RPN5a or RPN5b, indicating functional redundancy. However, abnormal phenotypes generated by overexpression implied that paralog-specific functions also exist. Collectively, the data point to a specific role for RPN5 in the plant 26S proteasome and suggest that its two paralogous genes in Arabidopsis have both redundant and unique roles in development.
26S蛋白酶体是一种重要的多催化蛋白酶复合体，可降解多种细胞内蛋白质，尤其是那些被泛素修饰的蛋白质。拟南芥和其他植物利用基因对来编码大多数核心亚基，两种同工型通常都会整合到成熟复合体中。在此，我们表明，编码调节颗粒非ATP酶亚基（RPN5）的基因对在蛋白酶体功能和拟南芥发育中具有独特作用。由于雄配子发生缺陷，无法产生纯合的rpn5a rpn5b突变体。虽然单个rpn5b突变体表现出野生型特征，但单个rpn5a突变体表现出一系列形态发生缺陷，包括异常胚胎发生、在黑暗中部分去黄化发育、在光照下生长时严重矮化的表型以及不育。缺少RPN5a的蛋白酶体复合体在体外稳定性较差，这表明rpn5a的一些缺陷是由复合体完整性改变引起的。rpn5a的表型可以通过RPN5a或RPN5b的表达来挽救，这表明存在功能冗余。然而，过表达产生的异常表型表明也存在旁系同源物特异性功能。总体而言，这些数据表明RPN5在植物26S蛋白酶体中具有特定作用，并表明其在拟南芥中的两个旁系同源基因在发育中具有冗余和独特的作用。
