Eukaryotic gene expression is controlled by a number of RNA-binding proteins (RBP), such as the proteins from the Puf (Pumilio and FBF) superfamily (PufSF). These proteins bind to RNA via multiple Puf repeat domains, each of which specifically recognizes a single RNA base. Recently, three diversified PufSF proteins have been described in model organisms, each of which is responsible for the maturation of ribosomal RNA or the translational regulation of mRNAs; however, less is known about the role of these proteins across eukaryotic diversity. Here, we investigated the distribution and function of PufSF RBPs in the tree of eukaryotes. We determined that the following PufSF proteins are universally conserved across eukaryotes and can be broadly classified into three groups: (i) Nop9 orthologues, which participate in the nucleolar processing of immature 18S rRNA; (ii) ‘classical’ Pufs, which control the translation of mRNA; and (iii) PUM3 orthologues, which are involved in the maturation of 7S rRNA. In nearly all eukaryotes, the rRNA maturation proteins, Nop9 and PUM3, are retained as a single copy, while mRNA effectors (‘classical’ Pufs) underwent multiple lineage-specific expansions. We propose that the variation in number of ‘classical’ Pufs relates to the size of the transcriptome and thus the potential mRNA targets. We further distinguished full set of PufSF proteins in divergent metamonad Giardia intestinalis and initiated their cellular and biochemical characterization. Our data suggest that the last eukaryotic common ancestor (LECA) already contained all three types of PufSF proteins and that ‘classical’ Pufs then underwent lineage-specific expansions.

中文翻译：

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整个真核生物中蛋白质Puf超家族的进化。

真核基因的表达受许多RNA结合蛋白（RBP）的控制，例如来自Puf（Pumilio和FBF）超家族（PufSF）的蛋白。这些蛋白质通过多个Puf重复域与RNA结合，每个域都特异性识别单个RNA碱基。最近，在模型生物中已经描述了三种多样化的PufSF蛋白，每种蛋白都负责核糖体RNA的成熟或mRNA的翻译调控。然而，人们对这些蛋白在真核生物多样性中的作用了解甚少。在这里，我们调查了PufSF RBPs在真核生物树中的分布和功能。我们确定以下PufSF蛋白在整个真核生物中都是保守的，可以大致分为三类：（i）Nop9直向同源物，参与未成熟的18S rRNA的核仁加工; （ii）控制mRNA翻译的“经典” Pufs；（iii）PUM3直向同源物，与7S rRNA的成熟有关。在几乎所有的真核生物中，rRNA成熟蛋白Nop9和PUM3被保留为单个拷贝，而mRNA效应子（“经典” Pufs）经历了多个谱系特异性扩增。我们提出，“经典” Puf的数量变化与转录组的大小有关，因此与潜在的mRNA靶标有关。我们进一步区分了完整的PufSF蛋白在发散的单核贾第鞭毛虫肠中，并开始了它们的细胞和生化特征。