Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, USA.
RNA. 2019 Nov;25(11):1549-1560. doi: 10.1261/rna.071811.119. Epub 2019 Aug 22.
The ribosomal protein Rpl1 (uL1 in universal nomenclature) is essential in yeast and constitutes part of the L1 stalk which interacts with E site ligands on the ribosome. Structural studies of nascent pre-60S complexes in yeast have shown that a domain of the Crm1-dependent nuclear export adapter Nmd3, binds in the E site and interacts with Rpl1, inducing closure of the L1 stalk. Based on this observation, we decided to reinvestigate the role of the L1 stalk in nuclear export of pre-60S subunits despite previous work showing that Rpl1-deficient ribosomes are exported from the nucleus and engage in translation. Large cargoes, such as ribosomal subunits, require multiple export factors to facilitate their transport through the nuclear pore complex. Here, we show that pre-60S subunits lacking Rpl1 or truncated for the RNA of the L1 stalk are exported inefficiently. Surprisingly, this is not due to a measurable defect in the recruitment of Nmd3 but appears to result from inefficient recruitment of the Mex67-Mtr2 heterodimer.
核糖体蛋白 Rpl1（通用命名法中的 uL1）在酵母中是必不可少的，它构成了与核糖体上 E 位配体相互作用的 L1 柄的一部分。酵母中新生 pre-60S 复合物的结构研究表明，Crm1 依赖性核输出适配器 Nmd3 的一个结构域结合在 E 位并与 Rpl1 相互作用，诱导 L1 柄的闭合。基于这一观察结果，我们决定重新研究 L1 柄在 pre-60S 亚基核输出中的作用，尽管先前的工作表明，缺乏 Rpl1 的核糖体从核内输出并参与翻译。大的货物，如核糖体亚基，需要多个出口因子来促进它们通过核孔复合体的运输。在这里，我们表明，缺乏 Rpl1 或 L1 柄 RNA 截断的 pre-60S 亚基的输出效率较低。令人惊讶的是，这不是由于 Nmd3 的招募出现可测量的缺陷，而是似乎是由于 Mex67-Mtr2 异二聚体的招募效率低下。
