Project description:N6-methyladenosine (m6A) is the most prevalent internal modification found in mammalian messenger and non-coding RNAs. The discoveries of functionally significant demethylases that reverse this methylation as well as the recently revealed m6A distributions in mammalian transcriptomes strongly indicate regulatory functions of this modification. Here we report the identification and characterization of the mammalian nuclear RNA N6-adenosine methyltransferase core (RNMTC) complex. Besides METTL3, a methyltransferase which was the only known component of RNMTC in the past, we discovered that a previously uncharacterized methyltransferase, METTL14, exhibits a N6-adenosine methyltransferase activity higher than METTL3. Together with WTAP, the third component that dramatically affects the cellular m6A level, these three proteins form the core complex that orchestrates m6A deposition on mammalian nuclear RNA. Biochemistry assays, imaging experiments, as well as transcriptome-wide analyses of the binding sites and their effects on m6A methylation support methylation function and reveal new insights of RNMTC. PAR-CLIP and m6A-seq in HeLa cells
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:The newly discovered dynamic N6-methyladenosine (m6A) modification plays a critical role in gene expression from a post-transcriptional level. we profiled the transcriptome-wide m6A modification in mRNAs and lncRNAs in non-targeting control A375 cells(NC) and METTL3 knockdown A375 cells(shMETTL3). Methylated RNA immunoprecipitation sequencing results revealed that the RNA m6A modification is conserved. METTL3 knockdown altered the expression of RNAs m6A modified sites in A375 cells. Finally, we show that the transcriptome-wide m6A alterations occurring in mRNAs and lncRNAs following METTL3 knockdown suggest this process plays important regulatory roles during A375 growth. This study provides a framework for applying the m6A modification regulated by METTL3 to melanoma research.
Project description:Oxaliplatin as a first-line drug frequently causes the chemo-resistance on colorectal cancer (CRC). N6-methyladenosine (m6A) methylation has been largely acknowledged in multiple biological functions. However, the molecular mechanisms underlying the m6A methylation in modulating anticancer drug resistance in CRC are still obscure. In present study, RIP-seq was conducted to investigate the occupancy of N6-methyladenosine RNA binding protein 3 (YTHDF3) served as “readers” that can recognize m6A modification site in HCT116 cells with oxaliplatin resistance (HCT116R). Then, YTHDF3 was knockdown by siRNA in HCT116 cells with oxaliplatin resistance, and RIP-seq was further conducted to investigate m6A methylation of HCT116, HCT116R and HCT116R cells with YTHDF3 knockdown.
Project description:Although internal PolyA RNA modification N6-methyladenosine (m6A) plays essential roles in diverse biological processes, technology to detect precise m6A sites at transcriptome-wide scale is lacking. Here, we discovered that m6A interferes A (Adenine) – U (Uracil) or A-T (Thymidine) pairing. Based on differential hybridization between methylated vs. unmethylated RNAs to a DNA probe, we developed tiling microarray to pinpoint m6A sites in mouse transcriptome. We validated some of the identified sites and provided evidence to suggest that one functional mechanism of m6A is to block small RNA targeting to methylated mRNA.
Project description:To explore the involvement of N6-methyladenosine (m6A) modification in circular RNAs (circRNAs) and relevant methyltransferases in the lesion of lens epithelium cells (LECs) under the circumstances of age-related cataract (ARC).
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:N6-methyladenosine (m6A), a major modification of messenger RNAs (mRNAs), plays critical roles in RNA metabolism and function. In addition to the internal m6A, N6, 2'-O-dimethyladenosine (m6Am) is present at the transcription start nucleotide of capped mRNAs in vertebrates. However, its biogenesis and functional role remain elusive. Using a reverse genetics approach, we identified PCIF1, a factor that interacts with the serine-5-phosphorylated carboxyl-terminal domain of RNA polymerase II, as a cap-specific adenosine methyltransferase (CAPAM) responsible for N6-methylation of m6Am. The crystal structure of CAPAM in complex with substrates revealed the molecular basis of cap-specific m6A formation. A transcriptome-wide analysis revealed that N6-methylation of m6Am promotes the translation of capped mRNAs. Thus, a cap-specific m6A writer promotes translation of mRNAs starting from m6Am.
Project description:N6-methyladenosine (m6A) is the most prevalent modification of eukaryotic cells st post-transcriptional level. The goals of this study are to compare the N6-methyladenosine modification of transcripts in normal and senescent nucleus pulposus cells using Me-RIP-seq
Project description:Emerging studies have revealed that N6-methyladenosine modification is involved in the development of various cancers. However, the m6A modification pattern of endometrioid ovarian cancer (EOC) has not been demonstrated. In the present study, high-throughput sequencing combined with methylated RNA immunoprecipitation (MeRIP-seq) and RNA sequencing were used to obtain the transcriptome-wide m6A modifications of endometrioid ovarian cancer for the first time.