Yahalom A, Kim T H, Winter E, Karniol B, von Arnim A G, Chamovitz D A
Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
J Biol Chem. 2001 Jan 5;276(1):334-40. doi: 10.1074/jbc.M006721200.
The Arabidopsis COP9 signalosome is a multisubunit repressor of photomorphogenesis that is conserved among eukaryotes. This complex may have a general role in development. As a step in dissecting the biochemical mode of action of the COP9 signalosome, we determined the sequence of proteins that copurify with this complex. Here we describe the association between components of the COP9 signalosome (CSN1, CSN7, and CSN8) and two subunits of eukaryotic translation initiation factor 3 (eIF3), eIF3e (p48, known also as INT-6) and eIF3c (p105). To obtain a biochemical marker for Arabidopsis eIF3, we cloned the Arabidopsis ortholog of the eIF3 subunit eIF3b (PRT1). eIF3e coimmunoprecipitated with CSN7, and eIF3c coimmunoprecipitated with eIF3e, eIF3b, CSN8, and CSN1. eIF3e directly interacted with CSN7 and eIF3c. However, eIF3e and eIF3b cofractionated by gel filtration chromatography in a complex that was larger than the COP9 signalosome. Whereas eIF3, as detected through eIF3b, localized solely to the cytoplasm, eIF3e, like CSN7, was also found in the nucleus. This suggests that eIF3e and eIF3c are probably components of multiple complexes and that eIF3e and eIF3c associate with subunits of the COP9 signalosome, even though they are not components of the COP9 signalosome core complex. This interaction may allow for translational control by the COP9 signalosome.
拟南芥COP9信号体是光形态建成的多亚基阻遏物，在真核生物中保守。该复合体可能在发育中起普遍作用。作为剖析COP9信号体生化作用模式的一步，我们确定了与该复合体共纯化的蛋白质序列。本文描述了COP9信号体（CSN1、CSN7和CSN8）的组分与真核翻译起始因子3（eIF3）的两个亚基eIF3e（p48，也称为INT-6）和eIF3c（p105）之间的关联。为了获得拟南芥eIF3的生化标记，我们克隆了eIF3亚基eIF3b（PRT1）的拟南芥直系同源物。eIF3e与CSN7共免疫沉淀，eIF3c与eIF3e、eIF3b、CSN8和CSN1共免疫沉淀。eIF3e直接与CSN7和eIF3c相互作用。然而，eIF3e和eIF3b通过凝胶过滤色谱在一个比COP9信号体更大的复合体中共同分级分离。通过eIF3b检测到的eIF3仅定位于细胞质，而eIF3e与CSN7一样，也存在于细胞核中。这表明eIF3e和eIF3c可能是多个复合体的组分，并且eIF3e和eIF3c与COP9信号体的亚基相关联，尽管它们不是COP9信号体核心复合体的组分。这种相互作用可能允许COP9信号体进行翻译控制。
