Specialized ribosomal protein genes promote drug resistance through modulation of translation

Ribosomes are ubiquitous ribonucleoprotein complexes required for protein synthesis. We show that in budding yeast exposure to drugs alters ribosome composition leading to modification of translation pattern and increased resistance to drug. Exposure to staurosporine repressed translation of cell wall protein genes. Expression of the major paralog of uL30/RPL7 increased cell sensitivity to staurosporine while expression of the minor paralog induced resistance. Remarkably, we found that differences in paralogs function was due to difference in the translation pattern. The minor paralog promoted the translation of cell wall genes with long open reading frames (ORFs), which are normally under-translated in the presence of the major paralog, leading to drug resistance. Reducing the ORF length repressed the minor paralog and staurosporine effects on translation. Together the data reveal a natural mechanism for the optimization of translation through changes in the identity of ribosomal protein genes. Total RNA and ribosome associated RNA from wild type cells and cells carrying two copies of either uL30A/RPL7A or uL30B/RPL7B grown in presence or absence of saturosporine was sequenced.

核糖体（ribosome）是一类广泛存在的核糖核蛋白复合物（ribonucleoprotein complex），为蛋白质合成所必需。本研究证实，在出芽酵母（budding yeast）中，药物暴露会改变核糖体的组成，进而引发翻译模式改变，并提升细胞对药物的耐药性。当细胞暴露于星形孢菌素（staurosporine）时，细胞壁蛋白基因的翻译会受到抑制。uL30/RPL7的主要旁系同源物（paralog）的表达会提高细胞对星形孢菌素的敏感性，而其次要旁系同源物的表达则可诱导细胞产生耐药性。值得注意的是，我们发现两类旁系同源物的功能差异源于其介导的翻译模式不同：次要旁系同源物可促进携带长开放阅读框（Open Reading Frame, ORF）的细胞壁基因的翻译，这类基因在主要旁系同源物存在时通常翻译不足，最终使细胞获得耐药性。缩短开放阅读框的长度，会抑制次要旁系同源物的作用，同时削弱星形孢菌素对翻译过程的影响。综上，本研究数据揭示了一种通过调整核糖体蛋白基因亚型来优化翻译过程的天然机制。本研究对在添加或不添加星形孢菌素的条件下培养的野生型细胞，以及分别携带两份uL30A/RPL7A或uL30B/RPL7B拷贝的细胞，提取其总RNA（total RNA）及核糖体结合RNA（ribosome associated RNA）并进行了测序。