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Exclusion of m6A from splice-site-proximal regions by the exon-junction complex dictates m6A topologies and mRNA stability

ABSTRACT: N6-methyladenosine (m6A), a widespread destabilizing mark on mRNA, is non-uniformly distributed across the transcriptome, yet the basis for its selective deposition is unknown. Here, we uncover that m6A deposition is not selective. Instead, m6A distribution is exclusion-based: m6A-consensus harboring sites are methylated by default, unless they are within a window of up to ~200 nt from an exon-intron junction. A simple model which we extensively validate, relying exclusively on presence of m6A motifs and exon-intron architecture allows high accuracy recapitulation of experimentally-measured m6A profiles and of the vast majority of m6A hallmarks. Finally, we provide strong evidence that this exclusion is mediated by the exon-junction complex. Our findings establish a mechanism by which the memory of nuclear RNA splicing is covalently etched on an mRNA in the form of m6A, and determines its cytoplasmic stability, with broad implications on the regulation, function, and evolution of the exon-junction complex and m6A.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE204980 | GEO | 2023/01/02

REPOSITORIES: GEO

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Exon Architecture Controls mRNA m6A Suppression and Gene Expression

Project description:N6–methyladenosine (m6A) is the most abundant mRNA modification and plays crucial roles in diverse physiological processes. Utilizing a Massively Parallel Assay for m6A (MPm6A), we discover that m6A specificity is globally regulated by “suppressors” that prevent m6A deposition in unmethylated transcriptome regions. We identify Exon Junction Complexes (EJCs) as m6A suppressors that protect exon junction-proximal RNA within coding sequences from methylation and regulate mRNA stability through m6A suppression. EJC suppression of m6A underlies multiple global characteristics of mRNA m6A specificity, with the local range of EJC protection sufficient to suppress m6A deposition in average-length internal exons, but not in long internal and terminal exons. EJC-suppressed methylation sites co-localize with EJC-suppressed splice sites, suggesting that exon architecture broadly determines local mRNA accessibility to regulatory complexes.

2023-02-01 | GSE162199 | GEO

m6A-seq on chromatin-assoicated RNA (ChrMeRIP-seq) in mouse embryonic stem cell [ChrMeRIP-seq]

Project description:N6-methyladenosines (m6A) are stoichiometrically deposited on exons of nearly one third of RNA Pol II transcriptome, mainly catalysed by METTL3/14 complex. However, neither the intronic methylation pattern and its functional relevance nor the immediate response upon m6A loss have been fully understood. Here we applied MeRIP-seq on mESC nascent transcriptome and thus revealed that approximately 6-10% of m6A peaks occurred at intronic regions, preferentially the conserved and alternative exon/intron part of longer introns, proximately to 5’-splice sites. These intronic m6A deposition correlates with both Rbm15 binding and H3K36me3. Moreover, coupled 4sU-seq with METTL3 dTAG system in mESC, we found that m6A mediates alternative exon/intron inclusive in nascent transcriptome. Intriguingly, m6A self-regulation including writers and readers are early response and partially contributed by alternative splicing changes. Collectively, our study presents a unified model that m6A mediates alternative splicing, and dTAG METTL3 opens an avenue to interrogate the direct response of functional m6A disruption.

2020-09-15 | GSE154706 | GEO

N6-Methyladenosine mediates alternative intron/exon inclusion in the nascent transcriptome [4sU-seq]

2020-09-15 | GSE154705 | GEO

Two zinc finger proteins with functions in m6A writing interact with HAKAI

Project description:The methyltransferase complex (m6A writer), which catalyzes the deposition of N6-methyladenosine (m6A) in mRNAs, is highly conserved across most eukaryotic organisms, but its components and interactions between them are still far from fully understood. Using in vivo interaction proteomics, two HAKAI-interacting zinc finger proteins, HIZ1 and HIZ2, were discovered as novel components of the Arabidopsis m6A writer complex. HAKAI is required for the interaction between HIZ1 and MTA. Whilst HIZ1 knockout plants have normal levels of m6A, plants in which it is overexpressed show reduced methylation. In addition, HIZ1 was found to be involved in root hair development upon auxin transport inhibition in a HAKAI-dependent manner. Mutant plants lacking HIZ2 are viable but have an 85% reduction in m6A abundance and show severe developmental defects. Our findings suggest that HIZ1 appears to be a HAKAI-dependent negative regulator of m6A deposition and HIZ2 is a novel and essential member of the Arabidopsis m6A writer complex.

2022-02-09 | PXD026287 | Pride

m6A full transcriptome map of human adenocarcinoma of esophagogastric junction

Project description:Here we systematically analyze the modification pattern of m6A mRNA in adenocarcinoma at the esophagogastric junction.In adenocarcinoma of esophagogastric junction samples, a total of 4775 new m6A peaks appeared, and 3054 peaks disappeared. The unique m6A-related genes in adenocarcinoma of esophagogastric junction are related to cancer-related pathways. There are hypermethylated or hypomethylated m6A peaks in AEG in differentially expressed mRNA transcripts. This study preliminarily constructed the first m6A full transcriptome map of human adenocarcinoma of esophagogastric junction. This has a guiding role in revealing the mechanism of m6A-mediated gene expression regulation.

2022-02-18 | GSE189874 | GEO

Activin/Nodal-dependent N6-methyladenosine (m6A) deposition in human pluripotent stem cells

Project description:This experiment was designed to probe the function of Activin/Nodal signalling in the deposition of m6A in human pluripotent stem cells (hPSCs). hPSCs were cultured in presence of Activin or subjected to short-term inhibition of Activin/Nodal signalling for 2h using the receptor antagonist SB-431542 (IP). The global abundance of m6A was then measured by nuclear-enriched methylated RNA immunoprecipitation followed by deep sequencing (NeMeRIP-seq). Pre-NeMeRIP input RNA was used as control to normalise for the changes in gene expression in the two conditions.

2017-12-26 | E-MTAB-5229 | biostudies-arrayexpress

Hakai is required for stabilization of core components of the m6A mRNA methylation machinery

Project description:N6-methyladenosine (m6A) is the most abundant internal modification on mRNA which influences most steps of mRNA metabolism and is involved in several biological functions. The E3 ubiquitin ligase Hakai was previously found in complex with components of the m6A methylation machinery in plants and mammalian cells but its precise function remained to be investigated. Here we show that Hakai is a conserved component of the methyltransferase complex in Drosophila and human cells. In Drosophila, its depletion results in reduced m6A levels and altered m6A-dependent functions including sex determination. We show that its ubiquitination domain is required for dimerisation and interaction with other members of the m6A machinery, while its catalytic activity is dispensable. Finally, we demonstrate that the loss of Hakai destabilizes several subunits of the methyltransferase complex, resulting in impaired m6A deposition. Our work adds new functional and molecular insights into the mechanism of the m6A mRNA writer complex.

2021-04-29 | PXD022294 | Pride

m6A-CLIP identified major presence of m6A in last exons

Project description:By adapting UV cross-linking immune precipitation for m6A (m6A-CLIP), we developed several novel genomic approaches with single-nucleotide resolution to accurately locate tens of thousands of m6A residues in human cells and mouse brain mRNAs. We found over 70% of these residues in the last exon with a very sharp rise (six-fold) within 150-400 nucleotides of the last exon, which overlaps the beginning of many 3′ untranslated region (UTRs). The 3′ UTRs contain ~two-thirds of the last exon m6A and 40 to 45% of the total of this base modification in mRNA. Contrary to earlier studies, we found no preference for location of m6A sites in the coding sequences around STOP codons. Many mRNA 3′ UTRs contain multiple polyA sites at least some of which are subject to regulated choices when cells change growth rate or differentiation state. The m6A density is at a peak early in the 3′ UTR and gradually diminishes in the more distal region of the last exon suggesting a possible inhibitory role of the proximal m6A residues to allow polyA choice of more distal polyA sites. This possibility was supported by finding that a main switch from distal to proximal polyA site choice is associated with m6A loss after triple knockdown of the m6A methylase complex. There is a significant overlap of m6A with identified binding sites for Ago complexes that carry microRNAs known to regulate mRNA stability which might possibly represent cooperation in function. With higher accuracy of m6A identification it is now more realistic to engage in highly localized mutagenesis to more definitively identify m6A function.

2015-09-28 | GSE71154 | GEO

The exon junction complex controls transposable element activity by ensuring faithful splicing of the piwi transcript

Project description:The exon junction complex (EJC) is a highly conserved ribonucleoprotein complex which binds RNAs during splicing and remains associated with them following export to the cytoplasm. While the role of this complex in mRNA localization, translation and degradation has been well characterized, its mechanism of action in splicing a subset of Drosophila and human transcripts remains to be elucidated. Here, we describe a novel function for the EJC and its splicing subunit RnpS1 in preventing transposon accumulation in both Drosophila germline and surrounding somatic follicle cells. This function is mediated specifically through the control of piwi transcript splicing, where in the absence of RnpS1 the fourth intron of piwi is retained. Within this intron the polypyrimidine tract is disrupted by a transposon-adjacent A/T-rich sequence that confers dependence on RnpS1. Finally, we demonstrate that RnpS1-dependent removal of this intron requires splicing of the flanking introns, suggesting a model in which the EJC facilitates the splicing of weak introns following its initial deposition at adjacent exon junctions. These data demonstrate a novel role for the EJC in regulating piwi intron excision and provide a mechanism for its function during splicing. Small-RNA libraries from two control samples and four knockdowns in germline or somatic tissues of the Drosophila melanogaster ovary.

2014-08-14 | E-GEOD-59327 | biostudies-arrayexpress

m6A level and isoform characterization sequencing (m6A-LAIC-seq) reveal the census and complexity of the m6A epitranscriptome

Project description:N6-methyladenosine (m6A) is a widespread reversible chemical modification of RNAs, implicated in many aspects of RNA metabolism. Little quantitative information exists as to either how many transcript copies of particular genes are m6A modified (âm6A levelsâ), or the relationship of m6A modification(s) to alternative RNA isoforms. To deconvolute the m6A epitranscriptome, we developed m6A level and isoform-characterization sequencing (m6A-LAIC-seq). We found that cells exhibit a broad range of non-stoichiometric m6A levels with cell type specificity. At the level of isoform characterization, we discovered widespread differences in use of tandem alternative polyadenylation (APA) sites by methylated and nonmethylated transcript isoforms of individual genes. Strikingly, there is a strong bias for methylated transcripts to be coupled with proximal APA sites, resulting in shortened 3â untranslated regions (3â-UTRs), while nonmethylated transcript isoforms tend to use distal APA sites. m6A-LAIC-seq yields a new perspective on transcriptome complexity and links APA usage to m6A modifications. m6A-LAIC-seq of H1-ESC and GM12878 cell lines, each cell line has two replicates

2016-06-24 | E-GEOD-66086 | biostudies-arrayexpress

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