Smith M Duane, Gu Yu, Querol-Audí Jordi, Vogan Jacob M, Nitido Adam, Cate Jamie H D
Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America.
PLoS One. 2013 Nov 8;8(11):e78715. doi: 10.1371/journal.pone.0078715. eCollection 2013.
Eukaryotic translation initiation factor 3 (eIF3) is a key regulator of translation initiation, but its in vivo assembly and molecular functions remain unclear. Here we show that eIF3 from Neurospora crassa is structurally and compositionally similar to human eIF3. N. crassa eIF3 forms a stable 12-subunit complex linked genetically and biochemically to the 13(th) subunit, eIF3j, which in humans modulates mRNA start codon selection. Based on N. crassa genetic analysis, most subunits in eIF3 are essential. Subunits that can be deleted (e, h, k and l) map to the right side of the eIF3 complex, suggesting that they may coordinately regulate eIF3 function. Consistent with this model, subunits eIF3k and eIF3l are incorporated into the eIF3 complex as a pair, and their insertion depends on the presence of subunit eIF3h, a key regulator of vertebrate development. Comparisons to other eIF3 complexes suggest that eIF3 assembles around an eIF3a and eIF3c dimer, which may explain the coordinated regulation of human eIF3 levels. Taken together, these results show that Neurospora crassa eIF3 provides a tractable system for probing the structure and function of human-like eIF3 in the context of living cells.
真核生物翻译起始因子3（eIF3）是翻译起始的关键调节因子，但其体内组装和分子功能仍不清楚。在此我们表明，粗糙脉孢菌的eIF3在结构和组成上与人类eIF3相似。粗糙脉孢菌eIF3形成一个稳定的12亚基复合物，在遗传和生化上与第13个亚基eIF3j相连，而在人类中，eIF3j调节mRNA起始密码子的选择。基于粗糙脉孢菌的遗传分析，eIF3中的大多数亚基是必不可少的。可以缺失的亚基（e、h、k和l）定位于eIF3复合物的右侧，这表明它们可能协同调节eIF3的功能。与该模型一致，亚基eIF3k和eIF3l作为一对被纳入eIF3复合物，它们的插入依赖于亚基eIF3h的存在，eIF3h是脊椎动物发育的关键调节因子。与其他eIF3复合物的比较表明，eIF3围绕eIF3a和eIF3c二聚体组装，这可能解释了人类eIF3水平的协同调节。综上所述，这些结果表明，粗糙脉孢菌eIF3为在活细胞环境中探究类人eIF3的结构和功能提供了一个易于处理的系统。
