GSE66011
Distinct NSun methylases control cytosine-5 methylation of messenger, mitochondrial and transfer RNA: implications for human diseases [miCLIP & Bisfulfite-Seq HEK293]
Aberrant post-transcriptional methylation is implicated in a wide range of human diseases, yet the specific enzymes responsible for site- and substrate-specific methylation remain largely unknown. Here, we use our recently developed catalysis-dependent RIP sequencing approach (miCLIP) and RNA bisulfite sequencing to map C5-methylcytosine (m5C) in the human transcriptome. We identified two novel m5C methylases NSun3 and NSun6, both of which have strong substrate specificity. In contrast to the previously characterized NSun2, which displays some preference to methylating transfer RNAs (tRNA), NSun6 predominantly targeted 3' UTRs of messenger RNAs (mRNA), and NSun3 mainly methylated mitochondrial RNAs (mtRNA). Consistent with the miCLIP-predicted RNA target specificity, whole exome sequencing identified NSUN3 loss-of-function mutations in a patient presenting with combined respiratory chain complex deficiency. Functional studies of the patient fibroblast cell line revealed that loss of the NSun3 protein resulted in severe mitochondrial translation defects, which were rescued by expression of wild-type NSun3. In summary, our results reveal how highly conserved NSun m5C methylases partition their substrate specificities to remodel the sequences of particular ribonucleotide classes. Overall design: Identification of Nsun3 and Nsun6 methylation targets by miCLIP and bisulfite sequencing in Embryonic kidney (HEK293) cells