Methylation of yeast ribosomal protein Rpl3 promotes translational elongation fidelity.
Methylation of yeast ribosomal protein Rpl3 promotes translational elongation fidelity.
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DOI：
10.1261/rna.054569.115
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发表时间：
2016-04
期刊：
影响因子：
--
通讯作者：
Clarke SG
中科院分区：
文献类型：
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作者：
Al-Hadid Q;Roy K;Chanfreau G;Clarke SG
Rpl 3是一种高度保守的核糖体蛋白，在酿酒酵母中被Hpm 1甲基转移酶在组氨酸243处甲基化。组氨酸243位于Rpl 3的功能重要区域中的肽基转移酶中心附近，该区域被指定为协调翻译延伸的解码、肽基转移和易位步骤的基本拇指。最近发现hpm 1参与核糖体的生物合成和翻译。然而，其Rpl 3底物甲基化的生物学作用尚未确定。在此，我们通过研究将该组氨酸残基突变为丙氨酸（rpl 3-H243 A）的功能影响来询问Rpl 3甲基化在H243处的作用。与Hpm 1缺陷细胞类似，rpl 3-H243 A细胞以类似的程度积累35 S和23 S前体rRNA前体，证实组氨酸甲基化在前体rRNA加工中的重要作用。相比之下，Hpm 1缺陷型细胞而非rpl 3-H243 A突变体显示核糖体亚基的扰动水平。我们发现，Hpm 1在不同的亚细胞组分中具有多种底物，这表明Rpl 3以外的蛋白质的甲基化对于控制核糖体亚基水平可能是重要的。最后，翻译保真度测定表明，与Hpm 1缺陷细胞一样，rpl 3-H243 A突变体在翻译延长中具有缺陷，导致翻译准确性降低。这些数据表明，H243处的Rpl 3甲基化在翻译延伸中起重要作用，可能通过基本拇指，但对核糖体亚基水平几乎没有影响。因此，hpm 1是一种多功能甲基转移酶，在核糖体生物合成和翻译中具有独立的作用。
Rpl3, a highly conserved ribosomal protein, is methylated at histidine 243 by the Hpm1 methyltransferase in Saccharomyces cerevisiae. Histidine 243 lies close to the peptidyl transferase center in a functionally important region of Rpl3 designated as the basic thumb that coordinates the decoding, peptidyl transfer, and translocation steps of translation elongation. Hpm1 was recently implicated in ribosome biogenesis and translation. However, the biological role of methylation of its Rpl3 substrate has not been identified. Here we interrogate the role of Rpl3 methylation at H243 by investigating the functional impact of mutating this histidine residue to alanine (rpl3-H243A). Akin to Hpm1-deficient cells, rpl3-H243A cells accumulate 35S and 23S pre-rRNA precursors to a similar extent, confirming an important role for histidine methylation in pre-rRNA processing. In contrast, Hpm1-deficient cells but not rpl3-H243A mutants show perturbed levels of ribosomal subunits. We show that Hpm1 has multiple substrates in different subcellular fractions, suggesting that methylation of proteins other than Rpl3 may be important for controlling ribosomal subunit levels. Finally, translational fidelity assays demonstrate that like Hpm1-deficient cells, rpl3-H243A mutants have defects in translation elongation resulting in decreased translational accuracy. These data suggest that Rpl3 methylation at H243 is playing a significant role in translation elongation, likely via the basic thumb, but has little impact on ribosomal subunit levels. Hpm1 is therefore a multifunctional methyltransferase with independent roles in ribosome biogenesis and translation.