Department of Molecular Biology, Science III, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland.
Department of Molecular Biology, Science III, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland.
Cell Rep. 2020 Aug 18;32(7):108038. doi: 10.1016/j.celrep.2020.108038.
The 5' end of eukaryotic mRNAs is protected by the mG-cap structure. The transcription start site nucleotide is ribose methylated (Nm) in many eukaryotes, whereas an adenosine at this position is further methylated at the N position (mA) by the mammalian Phosphorylated C-terminal domain (CTD)-interacting Factor 1 (PCIF1) to generate mAm. Here, we show that although the loss of cap-specific mAm in mice does not affect viability or fertility, the Pcif1 mutants display reduced body weight. Transcriptome analyses of mutant mouse tissues support a role for the cap-specific mAm modification in stabilizing transcripts. In contrast, the Drosophila Pcif1 is catalytically dead, but like its mammalian counterpart, it retains the ability to associate with the Ser5-phosphorylated CTD of RNA polymerase II (RNA Pol II). Finally, we show that the Trypanosoma Pcif1 is an mAm methylase that contributes to the N,N,2'-O-trimethyladenosine (mAm) in the hypermethylated cap4 structure of trypanosomatids. Thus, PCIF1 has evolved to function in catalytic and non-catalytic roles.
真核生物 mRNAs 的 5' 端受到 mG-帽结构的保护。在许多真核生物中，转录起始位点核苷酸被核糖甲基化（Nm），而在这个位置的一个腺嘌呤进一步被哺乳动物磷酸化 C 端结构域（CTD）相互作用因子 1（PCIF1）在 N 位甲基化（mA），生成 mAm。在这里，我们表明，尽管小鼠中特定于帽的 mAm 的缺失不会影响生存能力或生育能力，但 Pcif1 突变体显示体重减轻。突变体小鼠组织的转录组分析支持帽特异性 mAm 修饰在稳定转录本中的作用。相比之下，果蝇的 Pcif1 是无催化活性的，但与哺乳动物的对应物一样，它保留了与 RNA 聚合酶 II（RNA Pol II）的 Ser5 磷酸化 CTD 结合的能力。最后，我们表明，锥虫的 Pcif1 是一种 mAm 甲基转移酶，有助于锥虫中超甲基化帽 4 结构中的 N，N，2'-O-三甲基腺嘌呤（mAm）。因此，PCIF1 已经进化到在催化和非催化作用中发挥作用。
