Fonds de la Recherche Scientifique (FRS-FNRS), Université Libre de Bruxelles, 1050 Bruxelles, Belgium.
Mol Cell. 2013 Aug 22;51(4):539-51. doi: 10.1016/j.molcel.2013.08.011.
Mature ribosomal RNAs (rRNAs) are produced from polycistronic precursors following complex processing. Precursor (pre)-rRNA processing has been extensively characterized in yeast and was assumed to be conserved in humans. We functionally characterized 625 nucleolar proteins in HeLa cells and identified 286 required for processing, including 74 without a yeast homolog. For selected candidates, we demonstrated that pre-rRNA processing defects are conserved in different cell types (including primary cells), defects are not due to activation of a p53-dependent nucleolar tumor surveillance pathway, and they precede cell-cycle arrest and apoptosis. We also investigated the exosome's role in processing internal transcribed spacers (ITSs) and report that 3' end maturation of 18S rRNA involves EXOSC10/Rrp6, a yeast ITS2 processing factor. We conclude that human cells adopt unique strategies and recruit distinct trans-acting factors to carry out essential processing steps, posing fundamental implications for understanding ribosomopathies at the molecular level and developing effective therapeutic agents.
成熟核糖体 RNA(rRNA) 是通过多顺反子前体经过复杂的加工而产生的。前体 (pre)-rRNA 的加工在酵母中得到了广泛的研究，并且被认为在人类中是保守的。我们在 HeLa 细胞中对 625 种核仁蛋白进行了功能表征，并鉴定出 286 种对加工必不可少的蛋白，其中包括 74 种在酵母中没有同源物的蛋白。对于选定的候选蛋白，我们证明了前 rRNA 加工缺陷在不同的细胞类型（包括原代细胞）中是保守的，这些缺陷不是由于 p53 依赖性核仁肿瘤监测途径的激活引起的，并且它们发生在细胞周期停滞和凋亡之前。我们还研究了外泌体在加工内部转录间隔区 (ITSs) 中的作用，并报告了 18S rRNA 的 3' 端成熟涉及 EXOSC10/Rrp6，这是一种酵母 ITS2 加工因子。我们的结论是，人类细胞采用了独特的策略，并招募了不同的反式作用因子来执行必要的加工步骤，这对在分子水平上理解核糖体病和开发有效的治疗药物具有重要意义。
