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Reversible methylation of m6Am in the 5′ cap controls mRNA stability

ABSTRACT: Internal bases in mRNA can be subjected to modifications that influence the fate of mRNA in cells. One of the most prevalent modified bases is found at the 5′ end of mRNA, at the first encoded nucleotide adjacent to the 7-methylguanosine cap. Here we show that this nucleotide, N6,2′-O-dimethyladenosine (m6Am), is a reversible modification that influences cellular mRNA fate. Using a transcriptome-wide map of m6Am we find that m6Am-initiated transcripts are markedly more stable than mRNAs that begin with other nucleotides. We show that the enhanced stability of m6Am-initiated transcripts is due to resistance to the mRNA-decapping enzyme DCP2. Moreover, we find that m6Am is selectively demethylated by fat mass and obesity-associated protein (FTO). FTO preferentially demethylates m6Am rather than N6-methyladenosine (m6A), and reduces the stability of m6Am mRNAs. Together, these findings show that the methylation status of m6Am in the 5′ cap is a dynamic and reversible epitranscriptomic modification that determines mRNA stability.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE78040 | GEO | 2016/12/21

SECONDARY ACCESSION(S): PRJNA312400

REPOSITORIES: GEO

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FTO-mediated cytoplasmic m6Am demethylation adjusts stem-like properties in colorectal cancer cell

Project description:Cancer stem cells (CSCs) are a small but critical cell population for cancer biology since they display inherent resistance to standard therapies and give rise to metastases. Despite accruing evidence establishing a link between deregulation of epitranscriptome-related players and tumorigenic process, the role of messenger RNA (mRNA) modifications dynamic in the regulation of CSC properties remains poorly understood. Here, we show that the cytoplasmic pool of fat mass and obesity-associated protein (FTO) impedes CSC abilities in colorectal cancer through its m6Am (N6,2'-O-dimethyladenosine) demethylase activity. While m6Am is strategically located next to the m7G-mRNA cap, its biological function is not well understood and has not been addressed in cancer. Low FTO expression in patient-derived cell lines elevates m6Am level in mRNA which results in enhanced in vivo tumorigenicity and chemoresistance. Inhibition of the nuclear m6Am methyltransferase, PCIF1/CAPAM, fully reverses this phenotype, stressing the role of m6Am modification in stem-like properties acquisition. FTO-mediated regulation of m6Am marking constitutes a novel, reversible pathway controlling CSC abilities. Altogether, our findings bring to light the first biological function of the m6Am modification and its potential adverse consequences for colorectal cancer management.

2021-01-20 | GSE165115 | GEO

Differential m6A, m6Am, and m1A Demethylation Mediated by FTO in Cell Nucleus and Cytoplasm

Project description:FTO, the first RNA demethylase discovered, mediates the demethylation of N6-methyladenosine (m6A), installed internally on messenger RNA, and N6,2′-O-dimethyladenosine (m6Am), occurring at the +1 position from the 5’ cap. Despite extensive recent research on FTO, its physiological impact on cellular processes has yet to be fully elucidated. Here, we demonstrate that the cellular distribution of FTO is distinct among different cell lines, which critically affects the access of FTO to different RNA substrates. FTO binds multiple RNA substrates, including mRNA, U6 RNA, and tRNA. It mainly targets internal m6A when located in the cell nucleus and preferentially demethylates m6Am when residing in the cytoplasm. The expression levels of transcripts containing internal m6A are associated with the alteration of the FTO more so than transcripts containing m6Am. We also discover that N1-methyladenosine (m1A) in tRNA is a main substrate of FTO, with the FTO-catalyzed demethylation of target tRNAs repressing protein synthesis. Collectively, FTO-mediated RNA demethylation affects both mRNA level and translation through distinct pathways.

2018-09-14 | GSE106395 | GEO

Identification of the m6Am Methyltransferase PCIF1 Reveals the Location and Functions of m6Am in the Transcriptome

Project description:mRNAs are regulated by nucleotide modifications that influence their cellular fate. Two of the most abundant modified nucleotides are N6-methyladenosine (m6A), found within mRNAs, and N6,2′-O-dimethyladenosine (m6Am), which is found at the first transcribed nucleotide. Distinguishing these modifications in mapping studies has been difficult. Here, we identify and biochemically characterize PCIF1, the methyltransferase that generates m6Am. We find that PCIF1 binds and is dependent on the m7G cap. By depleting PCIF1, we generated transcriptome-wide maps that distinguish m6Am and m6A. We find that m6A and m6Am misannotations arise from mRNA isoforms with alternative transcription start sites (TSSs). These isoforms contain m6Am that maps to “internal” sites, increasing the likelihood of misannotation. We find that depleting PCIF1 does not substantially affect mRNA translation but is associated with reduced stability of a subset of m6Am-annotated mRNAs. The discovery of PCIF1 and our accurate mapping technique will facilitate future studies to characterize m6Am’s function.

2019-07-03 | GSE122948 | GEO

Reversible methylation of m6Am in the 5′ cap controls mRNA stability

Project description:Reversible methylation of m6Am in the 5′ cap controls mRNA stability

| PRJNA312400 | ENA

m6A/m-Seq of mouse adult cortex of Mettl3 cKO or Fto cKO mice

Project description:N6-Methyladenosine (m6A) and N6,2′-O-dimethyladenosine (m6Am) are abundant mRNA modifications that regulate transcript processing and translation. The role of both, here termed m6A/m, in the stress response in the adult brain in vivo are currently unknown. Here, we investigated the effect of gene deletion of Mettl3, a m6A methyltransferase, and Fto, a m6A and m6Am demethlyase, induced in adulthood in excitatory neurons of the neocortex and hippocampus (Camk2a-Cre Mettl3 or Fto cKO) on the cortical epitranscriptome. PolyA-RNA-fragments from 3-5 replicates per group were processed both as m6A/m-sample (RNA immunoprecipiation RIP with an m6A and m6Am antibody) and RNA-input sample.

2018-07-10 | GSE113793 | GEO

Proteomics of HEPG2 cells following FTO overexpression and knockdown

Project description:Proteomics of HEPG2 cells following FTO overexpression and knockdown. Data accompany our paper entitled “Dynamic Regulation of N6,2′-O-dimethyladenosine (m6Am) in Obesity” scheduled for publication in Nature Communications, 2021

2021-10-27 | PXD029268 | Pride

mRNA-Seq of mouse Mettl3 cKO and Fto cKO hippocampus after fear conditioning

Project description:N6-Methyladenosine (m6A) and N6,2′-O-dimethyladenosine (m6Am) are abundant mRNA modifications that regulate transcript processing and translation. The role of both, here termed m6A/m, in the stress response in the adult brain in vivo are currently unknown. Here, we investigated the effect of gene deletion of Mettl3, a m6A methyltransferase, and Fto, a m6A and m6Am demethlyase, induced in adulthood in excitatory neurons of the CA1 and CA3 in the hippocampus (Nex-CreERT2 Mettl3 or Fto cKO) on the transcriptome of CA1 and CA3 as well as the transcriptomic response of the CA1 and CA3 transcriptome to fear conditioning.

2018-07-10 | GSE113796 | GEO

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

Project description: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.

2020-08-28 | GSE151229 | GEO

Coordination of mRNA and tRNA methylations by TRMT10A

Project description:The post-transcriptional modification of mRNA and tRNA provides an additional layer of regulatory complexity during gene expression. TRMT10A is a tRNA methyltransferase that installs N1-methylguanosine (m1G), while FTO performs demethylation on N6-methyladenosine (m6A) and N6,2'-O-dimethyladenosine (m6Am) in mRNA. We find that this tRNA methyltransferase TRMT10A interacts with mRNA demethylase FTO (ALKBH9), both in vitro and inside cells. Strikingly, depletion of TRMT10A not only led to decreased m1G in tRNA but also significantly increased m6A levels in mRNA. CLIP-seq results showed that TRMT10A shares a significant overlap of associated mRNAs with FTO, and these mRNAs have accelerated decay rates potentially through the regulation by specific m6A reader. Furthermore, transcripts with increased m6A upon TRMT10A ablation contain an overrepresentation of m1G9-containing tRNAs codons read by tRNAGln(TTG), tRNAArg(CCG), and tRNAThr(CGT). These findings collectively reveal the presence of coordinated mRNA and tRNA modifications and demonstrate a mechanism for regulating gene expression through the interactions between mRNA and tRNA modifying enzymes.

2020-04-22 | GSE146207 | GEO

An atlas of single-base-resolution N6-methyl-adenine methylomes redefines RNA demethylase function as suppressors of disruptive RNA methylation

Project description:Various methylases and demethylases catalyze methylation and demethylation of N6-methyladenosine (m6A) and N6,2?-O-dimethyladenosine (m6Am) but precise methylomes uniquely mediated by each methylase/demethylase are still lacking. Here, we developed m6A-Crosslinking-Exonuclease-sequencing (m6ACE-seq) to map m6A and m6Am at transcriptome-wide single-base-resolution. m6ACE-seq's ability to quantify relative differences in methylation levels across samples enabled the generation of a comprehensive atlas of distinct methylomes uniquely mediated by every individual known methylase/demethylase. We determined METTL16 to indirectly impact manifold methylation targets beyond its consensus target motif, and highlighted the importance of precision in mapping PCIF1-dependent m6Am. Rather than reverse RNA methylation, we found that both ALKBH5 and FTO demethylases instead maintain their regulated sites in an unmethylated steady-state. In FTO's absence, anomalous m6Am disrupts snRNA interaction with nuclear export machinery, potentially causing aberrant pre-mRNA splicing events. We propose a model whereby RNA demethylases ensure normal RNA metabolism by suppressing disruptive RNA methylation in the nucleus.

2019-09-20 | GSE124509 | GEO

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