Yahalom Avital, Kim Tae-Houn, Roy Bijoyita, Singer Ruth, von Arnim Albrecht G, Chamovitz Daniel A
Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Plant J. 2008 Jan;53(2):300-11. doi: 10.1111/j.1365-313X.2007.03347.x. Epub 2007 Dec 4.
The roles of individual eukaryotic translation initiation factor 3 (eIF3) subunits are largely unclear, although some are essential, while others are thought to have regulatory roles. The 'e' subunit, also known as Int-6/Int6, is a candidate for a regulatory subunit as it is not essential for translation initiation in yeasts. eIF3e associates with the COP9 signalosome, and localizes to the nucleus in certain tissues. To further elucidate the roles of eIF3e, we have taken a genetic approach using Arabidopsis as a model system. Overexpression of eIF3e results in defects similar to mutations in the COP9 signalosome. eIF3e protein, but not transcript, over accumulates in csn mutants, and eIF3e is degraded in a proteasome-dependent fashion. In vitro and in vivo assays suggest that excess eIF3e inhibits translation. We conclude that the COP9 signalosome maintains a precise regulation of eIF3e levels, which is necessary for normal development in Arabidopsis.
尽管个别真核生物翻译起始因子3（eIF3）亚基的作用在很大程度上尚不清楚，其中一些亚基是必不可少的，而另一些亚基则被认为具有调节作用。“e”亚基，也称为Int-6/Int6，是调节亚基的一个候选者，因为它对酵母中的翻译起始不是必需的。eIF3e与COP9信号体相关联，并在某些组织中定位于细胞核。为了进一步阐明eIF3e的作用，我们采用了以拟南芥为模型系统的遗传学方法。eIF3e的过表达导致与COP9信号体突变相似的缺陷。eIF3e蛋白而非转录本在csn突变体中过度积累，并且eIF3e以蛋白酶体依赖性方式降解。体外和体内试验表明，过量的eIF3e会抑制翻译。我们得出结论，COP9信号体维持对eIF3e水平的精确调节，这对拟南芥的正常发育是必要的。
