The 5' end of eukaryotic mRNAs is protected by the m7G-cap structure. The transcription start site nucleotide is ribose methylated (Nm) in many eukaryotes, while an adenosine at this position is further methylated at the N6 position (m6A) by the mammalian Phosphorylated CTD-interacting Factor 1 (PCIF1) to generate m6Am. Here we show that while loss of cap-specific m6Am 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 m6Am 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 pol II. Finally, we show that the Trypanosoma Pcif1 is an m6Am methylase that contributes to the N6,N6,2?-O-trimethyladenosine (m62Am) in the hypermethylated cap4 structure of Trypanosomatids. Thus, PCIF1 has evolved to function in catalytic and non-catalytic roles. SOURCE: Ramesh Pillai (ramesh.pillai@unige.ch) -  University of Geneva

Pluto Bioinformatics

GSE151229: The mammalian cap-specific m6Am RNA methyltransferase PCIF1 regulates transcript levels in mouse tissues