Programa de Biologia Estrutural, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
Programa de Biologia Molecular e Biotecnologia, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
J Biol Chem. 2021 Jan-Jun;296:100586. doi: 10.1016/j.jbc.2021.100586. Epub 2021 Mar 24.
Previous work has suggested that highly positively charged protein segments coded by rare codons or poly (A) stretches induce ribosome stalling and translational arrest through electrostatic interactions with the negatively charged ribosome exit tunnel, leading to inefficient elongation. This arrest leads to the activation of the Ribosome Quality Control (RQC) pathway and results in low expression of these reporter proteins. However, the only endogenous yeast proteins known to activate the RQC are Rqc1, a protein essential for RQC function, and Sdd1, a protein with unknown function, both of which contain polybasic sequences. To explore the generality of this phenomenon, we investigated whether the RQC complex controls the expression of other proteins with polybasic sequences. We showed by ribosome profiling data analysis and western blot that proteins containing polybasic sequences similar to, or even more positively charged than those of Rqc1 and Sdd1, were not targeted by the RQC complex. We also observed that the previously reported Ltn1-dependent regulation of Rqc1 is posttranslational, independent of the RQC activity. Taken together, our results suggest that RQC should not be regarded as a general regulatory pathway for the expression of highly positively charged proteins in yeast.
先前的工作表明，由稀有密码子或多聚（A）延伸编码的高度带正电荷的蛋白质片段通过与带负电荷的核糖体出口通道的静电相互作用诱导核糖体停滞和翻译暂停，导致延伸效率低下。这种暂停导致核糖体质量控制（RQC）途径的激活，并导致这些报告蛋白的低表达。然而，已知唯一能激活 RQC 的内源性酵母蛋白是 Rqc1，它是 RQC 功能所必需的蛋白，以及 Sdd1，一种具有未知功能的蛋白，两者都含有多碱性序列。为了探索这种现象的普遍性，我们研究了 RQC 复合物是否控制其他含有多碱性序列的蛋白质的表达。我们通过核糖体谱数据分析和 Western blot 表明，含有类似于 Rqc1 和 Sdd1 的多碱性序列的蛋白质，甚至是带正电荷更多的蛋白质，不受 RQC 复合物的靶向。我们还观察到，先前报道的 Ltn1 对 Rqc1 的依赖性调节是翻译后调节，与 RQC 活性无关。总之，我们的结果表明，RQC 不应被视为酵母中高度带正电荷蛋白质表达的一般调节途径。
