Project description:Here we report a metabolic labeling method to map mRNA N6-methyladenosine (m6A) modification transcriptome-wide at base resolution, termed m6A-label-seq. The cells were fed with Se-allyl-L-selenohomocysteine, an analog of methoine, which serves as the precursor of methylation enzyme cofactor, so that cellular RNAs were continuously deposited with N6-allyladenosine (a6A) at supposed m6A sites. We enriched a6A-containing mRNAs and sequenced their a6A sites which are identical to m6A sites, based on iodination-induced misincorporation during reverse transcription.
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
Project description:Aim: To systematically classify the profile of the RNA m6A modification landscape of neonatal heart regeneration. Materials and Methods: Cardiomyocyte proliferation markers were detected via immunostaining. The expression of m6A modification regulators was detected using quantitative real-time PCR (qPCR) and Western blotting. Genome-wide profiling of m6A-modified transcripts was conducted with m6A-modified RNA immunoprecipitation sequencing (m6A-RIP-seq) and RNA sequencing (RNA-seq). The Gene Expression Omnibus database (GEO) dataset was used to verify the hub genes. Results: METTL3 and the level of m6A modification in total RNA were lower in P7 rat hearts than in P0 ones. In all, 1637 m6A peaks were differentially expressed using m6A-RIP-seq, with 84 upregulated and 1553 downregulated. Furthermore, conjoint analyses of m6A-RIP-seq, RNA-seq, and GEO data generated eight potential hub genes with differentially expressed hypermethylated or hypomethylated m6A levels. Conclusion: Our data show novel information on m6A modification changes in cardiac regeneration. The modifications made possible by directly modulating m6A may attract future study of cardiac regeneration.
Project description:N6-methyladenosine (m6A) is one of the most abundant mRNA modifications in eukaryotes, related to pivotal RNA metabolism processes. The most popular high-throughput m6A identification method relies on the commercial m6A antibody but suffers from poor reproducibility and limited resolution. Exact location of m6A site is of great vital for understanding the dynamics, functions and machinery of RNA methylation. Here, we developed a precise and high-throughput antibody-independent m6A identification method based on the m6A-sensitive RNA endoribonuclease recognizing ACA motif (m6A-sensitive RNA-Endoribonuclease–Facilitated sequencing or m6A-REF-seq). Whole-transcriptomic single base m6A map generated by m6A-REF-seq displayed a typical distribution pattern with enrichment adjacent to stop codon. Ligase-based and qPCR validation methods were used to confirm the individual m6A sites and quantify the methylation level, reinforcing the high accuracy of m6A-REF-seq. We applied m6A-REF-seq on five tissues from three mammals, showing that m6A sites were conserved and tend to gather together among species. (m6A-REF-seq had been named as Aim-seq.)
Project description:To find the m6A methylation targets of ABRO1, we performed m6A methylated RNA immunoprecipitation sequencing (MeRIP-seq) in ABRO1 Knockout or Wild type (WT) mice heart. The analysis of the distribution of m6A peak density in mRNA transcripts showed that m6A peaks are mainly found in coding sequences (CDS) and a considerable amount of m6A peaks enriched around start codon and stop codon regions in mRNA transcripts from ABRO1 KO and WT hearts. Among the total RNA transcripts with m6A sites, more than half (59.4%) of mRNA transcripts contain ≤ 2 m6A peaks, 27.4% mRNA transcripts comprise 3 to 5 m6A peaks and more than 5 m6A peaks exist in 13.2% of mRNA transcripts. MeRIP-seq analysis results from ABRO1 deleted hearts showed that a total of 3444 m6A peaks were upregulated and 4631 m6A were downregulated compared to WT hearts.
Project description:One of the most abundant RNA modifications is N6-methyladenosine (m6A). RNA from all forms of life, including viruses, contain m6A. This modification has been detected in many types of RNAs, such as mRNA, ribosomal RNA, long non-coding RNAs, small nuclear RNAs and microRNAs. Diverse set of proteins have been characterized to methylate, demethylate and specifically bind to this modification in different organisms. C. elegans is a unique model organism with abundant m6A modification, although its genome does not code for orthologs of the well characterized m6A methyltransferase METTL3/METTL14 complex or the demethylases FTO or ALKBH5. Furthermore, orthologs of the YTH family m6A reader proteins seem to be absent from the worm genome as well. To gain insights into how this modification is installed in this organism, we set out to identify enzymes that contribute to the abundant level of m6A in C. elegans. We designed a targeted RNAi screen by which the expression of 22 candidate putative RNA methyltransferase genes are knocked down. We measured global RNA methylation level by HPLC-MS/MS analysis after two generations of RNAi-mediated knock down. The knock down of two candidate methyltransferases resulted in a decrease in global m6A level in total RNA. The first methyltransferase, F33A8.4, is an ortholog of the human ZCCHC4 gene. The second methyltransferase, C38D4.9, is an ortholog of the human METTL5 gene. In order to determine if ZCCHC4 or METTL5 are involved in the deposition of m6A at the mRNA level, m6A-RIP-seq experiments were performed in mRNA derived from WT (N2), ZCCHC4 KO, METTL5 KO and ZCCHC4/METTL5 dKO C. elegans embryos.
Project description:Here, we profiled N6-methyladenosine (m6A) deposition on nascent RNAs in human cells by a new method MINT-Seq, which revealed that many classes of RTE RNAs, particularly intronic LINE-1s (L1s), are strongly methylated. These m6A-marked intronic L1s (MILs) are evolutionarily young, sense-oriented to hosting genes and nucleate a dozen RNA binding proteins (RBPs) that are putative novel m6A readers, including a nuclear matrix protein SAFB. Notably, m6A positively controls the expression of both autonomous L1s and co-transcribed L1 relics, promoting L1 retrotransposition. We showed that MILs preferentially reside in long genes, where they act as transcriptional ‘roadblock’ to impede the hosting gene expression, revealing a novel host-weakening strategy by the L1s. In counteraction, the host uses the SAFB reader complex to bind m6A-L1s to reduce their levels, and to safeguard hosting gene transcription.
Project description:To elucidate the molecular mechanism by which cardiac-hypertrophy-associated piRNA (CHAPIR) regulates m6A modification, we performed m6A methylated RNA immunoprecipitation sequencing (MeRIP-seq) in control or CHAPIR-overexpressing mice heart. The sequential analysis of m6A peaks showed that RGACH motif was highly enriched within m6A sites in heart and that is aligning with the classical consensus sequence of mammals ‘RGACH’, where ‘R’ indicates purine (A/G) and ‘H’ indicates non-guanine base (A/C/U). In CHAPIR treated heart, m6A mostly occurred in mRNAs (89.5%) and only about 10.5% were identified in non-coding RNAs. The majority of mRNAs contain one or two m6A peaks (89.2%) and 10.8% mRNA contain >2 m6A peaks . M6A peaks were predominantly distributed in coding sequences (CDSs), 3’ untranslated regions (3’UTRs) and near stop codon.
Project description:N6-methyladenosine (m6A) is one of the most abundant modifications in eukaryotic RNA. Recent mapping of m6A methylomes in mammals, yeast, and plants as well as characterization of m6A methyltransferases, demethylases, and binding proteins have revealed regulatory functions of this dynamic RNA modification. In bacteria, although m6A is present in ribosomal RNA (rRNA), its occurrence in messenger RNA (mRNA) still remains elusive. Here, we used liquid chromatography-mass spectrometry (LC-MS) to calculate the m6A/A ratio in mRNA from a wide range of bacterial species, which demonstrates that m6A is an abundant mRNA modification in tested bacteria. Subsequent transcriptome-wide m6A profiling in Escherichia coli and Pseudomonas aeruginosa revealed a conserved distinct m6A pattern that is significantly different from that in eukaryotes. Most m6A peaks are located inside open reading frames (ORF), and carry a unique consensus motif (GCCAU). Functional enrichment analysis of bacterial m6A peaks indicates that the majority of m6A-modified transcripts are associated with respiration, amino acids metabolism, stress response, and small RNAs genes, suggesting potential regulatory roles of m6A in these pathways. m6A profiling in E.coli and P.aeruginosa mRNA
Project description:m6A is a ubiquitous RNA modification in eukaryotes. Transcriptome-wide m6A patterns in Arabidopsis have been assayed recently. However, m6A differential patterns among organs have not been well characterized. The goal of the study is to comprehensively analyze m6A patterns of numerous types of RNAs, the relationship between transcript level and m6A methylation extent, and m6A differential patterns among organs in Arabidopsis. In total, 18 libraries were sequneced. For the 3 organs: leaf, flower and root, each organ has mRNA-Seq, m6A-Seq and Input sequenced. And each sequence has 2 replicats.