A Quantitative Sequencing Method for 5-Formylcytosine in RNA
Ontology highlight
ABSTRACT: 5-Formylcytosine (f5C) modification is present in human mitochondrial methionine tRNA (mt-tRNAMet) and cytosolic leucine tRNA (ct-tRNALeu), with their formation mediated by NSUN3 and ALKBH1. f5C has also been detected in mRNA of yeast and human cells, but its transcriptome-wide distribution has not been studied. Here we report f5C-seq, a quantitative sequencing method to map f5C transcriptome-wide in HeLa and mouse embryonic stem cells (mESCs). We show that f5C in RNA can be reduced to dihydrouracil (DHU) by pico-brane, and DHU can be exclusively read as U during reverse transcription (RT) reaction, allowing the detection and quantification of f5C sites by a unique C-to-U mutation signature. We validated f5C-seq by identifying and quantifying the two known f5C sites in tRNA, in which the f5C modification fractions dropped significantly in ALKBH1-depleted cells. By applying f5C-seq to small RNA, we identified 13 and 11 new f5C sites in HeLa and mESC tRNA, respectively.
ORGANISM(S): Mus musculus synthetic construct Homo sapiens
Project description:Mitochondrial gene expression uses a non-universal genetic code in mammals. Besides reading the conventional AUG codon, mitochondrial (mt-)tRNAMet mediates incorporation of methionine on AUA and AUU codons during translation initiation and on AUA codons during elongation. We show that the RNA methyltransferase NSUN3 localises to mitochondria and interacts with mt-tRNAMet to methylate cytosine 34 (C34) at the wobble position. NSUN3 specifically recognises the anticodon stem loop (ASL) of the tRNA, explaining why a mutation that compromises ASL basepairing leads to disease. We further identify ALKBH1/ABH1 as the dioxygenase responsible for oxidising m5C34 of mt-tRNAMet to generate an f5C34 modification. In vitro codon recognition studies with mitochondrial translation factors reveal preferential utilization of m5C34 mt-tRNAMet in initiation. Depletion of either NSUN3 or ABH1 strongly affects mitochondrial translation in human cells, implying that modifications generated by both enzymes are necessary for mt-tRNAMet function. Together, our data reveal how modifications in mt-tRNAMet are generated by the sequential action of NSUN3 and ABH1, allowing the single mitochondrial tRNAMet to recognise the different codons encoding methionine. HEK293 cell lines expressing His-FLAG-tagged NSUN3 or the His-FLAG tag alone were crosslinked using UV or treated with 5-azacytidine and analysed by CRAC
Project description:Mitochondrial gene expression uses a non-universal genetic code in mammals. Besides reading the conventional AUG codon, mitochondrial (mt-)tRNAMet mediates incorporation of methionine on AUA and AUU codons during translation initiation and on AUA codons during elongation. We show that the RNA methyltransferase NSUN3 localises to mitochondria and interacts with mt-tRNAMet to methylate cytosine 34 (C34) at the wobble position. NSUN3 specifically recognises the anticodon stem loop (ASL) of the tRNA, explaining why a mutation that compromises ASL basepairing leads to disease. We further identify ALKBH1/ABH1 as the dioxygenase responsible for oxidising m5C34 of mt-tRNAMet to generate an f5C34 modification. In vitro codon recognition studies with mitochondrial translation factors reveal preferential utilization of m5C34 mt-tRNAMet in initiation. Depletion of either NSUN3 or ABH1 strongly affects mitochondrial translation in human cells, implying that modifications generated by both enzymes are necessary for mt-tRNAMet function. Together, our data reveal how modifications in mt-tRNAMet are generated by the sequential action of NSUN3 and ABH1, allowing the single mitochondrial tRNAMet to recognise the different codons encoding methionine.
Project description:Epitranscriptomic RNA modifications can regulate fundamental biological processes, but we lack approaches to map modification sites and probe writer enzymes. Here we present a chemoproteomic strategy to characterize RNA 5-methylcytidine (m5C) dioxygenase enzymes in their native context based upon metabolic labeling and activity-based crosslinking with 5-ethynylcytidine (5-EC), RNA-protein enrichment, and quantitative proteomics. We profile m5C dioxygenases in human cells including ALKBH1 and TET2 and use quantitative nucleoside LC-MS to show that ALKBH1 is the major hm5C and f5C-forming enzyme in RNA, including upon polyadenylated RNA. Further, we map ALKBH1 modification sites transcriptome-wide using 5-EC-based iCLIP analysis to show that ALKBH1 oxidizes m5C in a variety of tRNA anticodon stem loops (ASL), as well as on mRNA and lncRNA, and analyze its substrate specificity using in vitro enzymatic assays. Finally, we apply pyridine borane-mediated sequencing to identify f5C sites in tRNA ASLs. Our work provides powerful chemical approaches for studying RNA m5C dioxygenases and mapping oxidative m5C modifications and reveals the existence of novel epitranscriptomic pathways for regulating RNA function.
Project description:5-Formylcytidine (f5C) is one type of post-transcriptional RNA modifi-cations, which is known at the wobble position of tRNA in mitochon-dria and essential for mitochondrial protein synthesis. Here, we show a method to detect f5C modifications in RNA and a transcriptome-wide f5C mapping technique, named f5C-seq. It is developed based on the treatment of pyridine borane, which can reduce f5C to 5,6-dihydrouracil (DHU), thus inducing C-to-T transition in f5C sites during PCR to achieve single-base resolution detection. Thousands of f5C sites were identified after mapping in Saccharomyces cerevisiae by f5C-seq. Moreover, codon composition demonstrated a preference for f5C within wobble sites in mRNA, suggesting the potential role in regulation of translation. These findings expand the scope of the understanding of cytosine modifications in mRNA. Reference build: S288C_reference_genome_R64-2-1_20150113
Project description:AlkB homolog 1 (ALKBH1) has been reported to act as a DNA 6mA demethylase to remove 6mA modification in eukaryotic genomes. Our previous data showed downregulated ALKBH1 in mouse and human fatty liver and increased DNA 6mA levels in mouse fatty liver. We developed liver-specific ALKBH1 knockout (AKO) mice to directly study the role of ALKBH1 mediated DNA 6mA modification during the development of hepatic steatosis. Deletion of liver ALKBH1 promoted hepatic steatosis and insulin resistance. Overexpression of ALKBH1 resulted in opposite phenotypes. To investigate the mechanism of ALKBH1 in regulating target gene expression. We performed ChIP-seq for identifying ALKBH1 binding sites on mouse hepatocytes genomes and validated its demethylase activity for DNA 6mA modification on the target genes via ChIP-qPCR assays.
Project description:Here we report m5C-TAC-seq, a base-resolution sequencing method to directly detect m5C sites without affecting unmodified C. In m5C-seq, we combined TET-mediated oxidation of RNA m5C to f5C with the selective chemical labeling reaction of f5C, enabling both pre-enrichment of m5C-containing RNA and a m5C-to-T transition in reverse transcription. m5C-seq identifies 2,500 sites in the transcriptome of HeLa and 768 sites in the transcriptome-wide of HEK293T. In addition, taking advantage of barcoding and pooling strategy, m5C-seq detected differential m5C sites upon specific methyltransferases depletion in mESCs and dynamically regulated m5C sites under cell fate transition. Moreover, we also detected 215 sites in chromatin-associated RNAs, demonstrating that portion of m5C sites can be co-transcriptionally catalyzed and the existence of m5C methylations in repeat RNAs.
Project description:Transfer RNA (tRNA) modifications are crucial for protein synthesis, but their physiological roles remain poorly understood. Here we investigate the impact of N4-acetylcytidine (ac4C), a highly conserved tRNA modification, using a Thumpd1 knockout mouse model. We find that loss of Thumpd1-dependent tRNA acetylation leads to reduced levels of tRNALeu, increased ribosome stalling and collisions, and activation of eIF2α phosphorylation. Thumpd1 knockout mice exhibit growth defects and sterility. Remarkably, concurrent knockout of Thumpd1 and the stress-sensing kinase Gcn2 causes penetrant postnatal lethality, revealing a critical genetic interaction. Our findings demonstrate that a modification restricted to a single site within type II cytosolic tRNAs can regulate ribosome-mediated signaling in mammalian organisms. By providing insight into how tRNA modifications shape signaling and cell fate in response to stress, this work opens up novel strategies for therapeutic intervention and translational control.
Project description:Transfer RNA (tRNA) modifications are crucial for protein synthesis, but their position-specific physiological roles remain poorly understood. Here, we investigate the impact of N4-acetylcytidine (ac4C), a highly conserved tRNA modification catalyzed by the essential acetyltransferase Nat10. By targeting Thumpd1, a nonessential adapter protein required for Nat10-catalyzed tRNA acetylation, we determine that loss of tRNA acetylation leads to reduced levels of tRNALeu, increased ribosome stalling, and activation of eIF2α phosphorylation. Thumpd1 knockout mice exhibit growth defects and sterility. Concurrent knockout of Thumpd1 and the stress-sensing kinase Gcn2 causes penetrant postnatal lethality in mice, indicating a critical genetic interaction. Our findings demonstrate that a modification restricted to a single position within type II cytosolic tRNAs can regulate ribosome-mediated stress signaling in mammalian organisms, with implications for our understanding of translational control and therapeutic interventions.
Project description:Transfer RNA (tRNA) modifications are crucial for protein synthesis, but their physiological roles remain poorly understood. Here we investigate the impact of N4-acetylcytidine (ac4C), a highly conserved tRNA modification, using a Thumpd1 knockout mouse model. We find that loss of Thumpd1-dependent tRNA acetylation leads to reduced levels of tRNALeu, increased ribosome stalling and collisions, and activation of eIF2α phosphorylation. Thumpd1 knockout mice exhibit growth defects and sterility. Remarkably, concurrent knockout of Thumpd1 and the stress-sensing kinase Gcn2 causes penetrant postnatal lethality, revealing a critical genetic interaction. Our findings demonstrate that a modification restricted to a single site within type II cytosolic tRNAs can regulate ribosome-mediated signaling in mammalian organisms. By providing insight into how tRNA modifications shape signaling and cell fate in response to stress, this work opens up novel strategies for therapeutic intervention and translational control.
Project description:Transfer RNA (tRNA) modifications are crucial for protein synthesis, but their position-specific physiological roles remain poorly understood. Here, we investigate the impact of N4-acetylcytidine (ac4C), a highly conserved tRNA modification catalyzed by the essential acetyltransferase Nat10. By targeting Thumpd1, a nonessential adapter protein required for Nat10-catalyzed tRNA acetylation, we determine that loss of tRNA acetylation leads to reduced levels of tRNALeu, increased ribosome stalling, and activation of eIF2α phosphorylation. Thumpd1 knockout mice exhibit growth defects and sterility. Concurrent knockout of Thumpd1 and the stress-sensing kinase Gcn2 causes penetrant postnatal lethality in mice, indicating a critical genetic interaction. Our findings demonstrate that a modification restricted to a single position within type II cytosolic tRNAs can regulate ribosome-mediated stress signaling in mammalian organisms, with implications for our understanding of translational control and therapeutic interventions.