Uncoupling of GTP hydrolysis from eIF6 release on the ribosome causes Shwachman-Diamond syndrome
Uncoupling of GTP hydrolysis from eIF6 release on the ribosome causes Shwachman-Diamond syndrome
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DOI：
10.1101/gad.623011
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发表时间：
2011-05-01
影响因子：
10.5
通讯作者：
Warren, Alan J.
中科院分区：
文献类型：
--
作者：
Finch, Andrew J.;Hilcenko, Christine;Warren, Alan J.
去除装配因子真核起始因子6（eIF 6）对于60 S核糖体亚基的晚期细胞质成熟至关重要。在哺乳动物细胞中，目前的模型假定eIF 6的释放是在Ser 235被活化的蛋白激酶C磷酸化后触发的。相比之下，酵母中的遗传研究表明需要SBDS（Shwachman-Bodian-Diamond综合征）基因的直系同源物，该基因在遗传性白血病易感性障碍Shwachman-Diamond综合征（SDS）中突变。在这里，通过从Sbds缺失小鼠中分离晚期细胞质60 S核糖体亚基，我们表明SBDS和GTP延伸因子样1（EFL 1）通过需要GTP结合和EFL 1水解但不磷酸化eIF 6 Ser 235的机制直接催化哺乳动物细胞中eIF 6的去除。对疾病相关错义变体的功能分析揭示，SBDS的基本作用是将核糖体上EFL 1的GTP水解与eIF 6释放紧密结合。此外，互补的NMR光谱研究表明，在60 S成熟的这一后期步骤和细菌核糖体解体方面之间存在意想不到的机制相似之处。我们的研究结果确立了SBDS和EFL 1在所有真核生物中催化核糖体翻译激活的直接作用，并将SDS定义为由eIF 6释放引起的解偶联GTP水解引起的核糖体病。
Removal of the assembly factor eukaryotic initiation factor 6 (eIF6) is critical for late cytoplasmic maturation of 60S ribosomal subunits. In mammalian cells, the current model posits that eIF6 release is triggered following phosphorylation of Ser 235 by activated protein kinase C. In contrast, genetic studies in yeast indicate a requirement for the ortholog of the SBDS (Shwachman-Bodian-Diamond syndrome) gene that is mutated in the inherited leukemia predisposition disorder Shwachman-Diamond syndrome (SDS). Here, by isolating late cytoplasmic 60S ribosomal subunits from Sbds-deleted mice, we show that SBDS and the GTPase elongation factor-like 1 (EFL1) directly catalyze eIF6 removal in mammalian cells by a mechanism that requires GTP binding and hydrolysis by EFL1 but not phosphorylation of eIF6 Ser 235. Functional analysis of disease-associated missense variants reveals that the essential role of SBDS is to tightly couple GTP hydrolysis by EFL1 on the ribosome to eIF6 release. Furthermore, complementary NMR spectroscopic studies suggest unanticipated mechanistic parallels between this late step in 60S maturation and aspects of bacterial ribosome disassembly. Our findings establish a direct role for SBDS and EFL1 in catalyzing the translational activation of ribosomes in all eukaryotes, and define SDS as a ribosomopathy caused by uncoupling GTP hydrolysis from eIF6 release.