Carmody Patrick, Roushar Francis J, Tedman Austin, Wang Wei, Herwig Madeline, Kim Minsoo, McDonald Eli F, Noguera Karen, Wong-Roushar Jennifer, Poirier Jon-Luc, Zelt Nathan B, Pockrass Ben T, McKee Andrew G, Kuntz Charles P, Raju S Vamsee, Plate Lars, Penn Wesley D, Schlebach Jonathan P
Department of Chemistry, Indiana University Bloomington, Bloomington, IN, USA 47401.
The James Tarpo Jr. and Margaret Tarpo Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907.
bioRxiv. 2024 Jul 23:2023.05.02.539166. doi: 10.1101/2023.05.02.539166.
The cotranslational misfolding of the cystic fibrosis transmembrane conductance regulator chloride channel (CFTR) plays a central role in the molecular basis of cystic fibrosis (CF). The misfolding of the most common CF variant (ΔF508) remodels both the translational regulation and quality control of CFTR. Nevertheless, it is unclear how the misassembly of the nascent polypeptide may directly influence the activity of the translation machinery. In this work, we identify a structural motif within the CFTR transcript that stimulates efficient -1 ribosomal frameshifting and triggers the premature termination of translation. Though this motif does not appear to impact the interactome of wild-type CFTR, silent mutations that disrupt this RNA structure alter the association of nascent ΔF508 CFTR with numerous translation and quality control proteins. Moreover, disrupting this RNA structure enhances the functional gating of the ΔF508 CFTR channel at the plasma membrane and its pharmacological rescue by the CFTR modulators contained in the CF drug Trikafta. The effects of the RNA structure on ΔF508 CFTR appear to be attenuated in the absence of the ER membrane protein complex (EMC), which was previously found to modulate ribosome collisions during "preemptive quality control" of a misfolded CFTR homolog. Together, our results reveal that ribosomal frameshifting selectively modulates the assembly, function, and pharmacological rescue of a misfolded CFTR variant. These findings suggest interactions between the nascent chain, quality control machinery, and ribosome may dynamically modulate ribosomal frameshifting in order to tune the processivity of translation in response to cotranslational misfolding.
囊性纤维化跨膜传导调节因子氯离子通道（CFTR）的共翻译错误折叠在囊性纤维化（CF）的分子基础中起着核心作用。最常见的CF变体（ΔF508）的错误折叠重塑了CFTR的翻译调控和质量控制。然而，尚不清楚新生多肽的错误组装如何直接影响翻译机器的活性。在这项工作中，我们在CFTR转录本中鉴定出一个结构基序，它刺激有效的-1核糖体移码并触发翻译的过早终止。尽管这个基序似乎不影响野生型CFTR的相互作用组，但破坏这种RNA结构的沉默突变会改变新生的ΔF508 CFTR与许多翻译和质量控制蛋白的关联。此外，破坏这种RNA结构增强了ΔF508 CFTR通道在质膜上的功能门控以及CF药物Trikafta中所含CFTR调节剂对其的药理学挽救作用。在没有内质网膜蛋白复合物（EMC）的情况下，RNA结构对ΔF508 CFTR的影响似乎减弱，之前发现EMC在错误折叠的CFTR同源物的“抢先质量控制”过程中调节核糖体碰撞。总之，我们的结果表明核糖体移码选择性地调节错误折叠的CFTR变体的组装、功能和药理学挽救作用。这些发现表明新生链、质量控制机制和核糖体之间的相互作用可能动态调节核糖体移码，以便根据共翻译错误折叠来调整翻译的持续性。
