Elucidating the role of Zuo1 protein on the translational control of gene expression in Saccharomyces cerevisiae

The ribosome associated complex (RAC) is a ribosome bound protein chaperone complex reported to surveil the translation of proteins with positively charged regions. It has been posited that RAC might be able to directly regulate translation by coupling co-translational folding with the peptide-elongation cycle. To identify the targets of RAC in cells and test the hypothesis that the complex modulates translation, we performed ribosome profiling on wild- type yeast cells and cells lacking a key component of the RAC that binds near the ribosome active site (zuo1Δ). Ribosome profiling is a sequencing-based technique that allows us to take a nucleotide resolution snapshot of where every ribosome sits on every mRNA in a cell at a given point in time. This powerful approach can provide information about the contributions of individual proteins to the translational landscape of a cell. We identified >300 targets for the RAC, and unexpectedly observed that the ribosome frameshifts on ~10% of these targets in zuo1Δ cells. The maintenance of ribosome reading frame is essential for cell health because frameshifts can result in the production of non-functional truncated and extended protein products. These studies have the potential to uncover RAC as a critical determinant of translational fidelity in eukaryotic cells.核糖体相关复合物（ribosome associated complex, RAC）是一类结合于核糖体的蛋白伴侣复合物，已有研究报道其可监控携带正电荷区域的蛋白质的翻译过程。已有假说提出，RAC或可通过将共翻译折叠与肽延伸循环相耦联，直接调控翻译进程。为鉴定细胞内RAC的靶标并验证该复合物可调控翻译的假说，我们对野生型酵母细胞，以及缺失核糖体活性位点附近结合的RAC关键组分的细胞（zuo1Δ）开展了核糖体谱分析（ribosome profiling）实验。核糖体谱分析是一种基于测序的技术，能够在特定时间点下，以核苷酸分辨率捕捉细胞内所有核糖体在每一条信使RNA（mRNA）上的定位快照。该高效研究手段可揭示单个蛋白对细胞翻译组的调控贡献。我们共鉴定出超过300个RAC的靶标，并意外观察到，在zuo1Δ突变体细胞中，约10%的靶标会发生核糖体移码。维持核糖体阅读框的正确性对细胞存活至关重要，因为移码会导致产生无功能的截短型及延长型蛋白产物。本研究有望揭示RAC作为真核细胞翻译保真性关键调控因子的潜在作用。