Institute of Cell Biology, University of Bern, Bern, Switzerland.
Graduate School of Cellular and Biomedical Science, University of Bern, Bern, Switzerland.
Nucleic Acids Res. 2019 Feb 28;47(4):1725-1739. doi: 10.1093/nar/gky1255.
The path from DNA to RNA to protein in eukaryotes is guided by a series of factors linking transcription, mRNA export and translation. Many of these are conserved from yeast to humans. Trypanosomatids, which diverged early in the eukaryotic lineage, exhibit unusual features such as polycistronic transcription and trans-splicing of all messenger RNAs. They possess basal transcription factors, but lack recognisable orthologues of many factors required for transcription elongation and mRNA export. We show that retrotransposon hotspot (RHS) proteins fulfil some of these functions and that their depletion globally impairs nascent RNA synthesis by RNA polymerase II. Three sub-families are part of a coordinated process in which RHS6 is most closely associated with chromatin, RHS4 is part of the Pol II complex and RHS2 connects transcription with the translation machinery. In summary, our results show that the components of eukaryotic transcription are far from being universal, and reveal unsuspected plasticity in the course of evolution.
真核生物中从 DNA 到 RNA 再到蛋白质的途径受到一系列连接转录、mRNA 输出和翻译的因子的指导。这些因子中的许多在酵母到人类中都是保守的。在真核生物谱系中早期分化的动质体表现出不寻常的特征，例如多顺反子转录和所有信使 RNA 的转位拼接。它们具有基本转录因子，但缺乏转录延伸和 mRNA 输出所需的许多因子的可识别同源物。我们表明逆转录转座子热点 (RHS) 蛋白发挥了其中一些功能，并且它们的耗竭会全局损害 RNA 聚合酶 II 新生 RNA 的合成。三个亚家族参与一个协调的过程，其中 RHS6 与染色质最密切相关，RHS4 是 Pol II 复合物的一部分，而 RHS2 将转录与翻译机制连接起来。总之，我们的结果表明，真核转录的组成远非普遍存在，并揭示了进化过程中出人意料的可塑性。
