GO:0036396 RNA N6-methyladenosine methyltransferase complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0036396 defines the RNA N6-methyladenosine (m6A) methyltransferase complex, the writer complex that deposits m6A on RNA.
• In vertebrates, the core complex comprises METTL3, METTL14, and WTAP, with accessory subunits including ZC3H13, VIRMA, CBLL1/HAKAI, and RBM15/RBM15B.
• The complex catalyzes methylation of adenosine to N6-methyladenosine, a reversible post-transcriptional modification that affects RNA stability, splicing, and translation.
• Dysregulation of the m6A writer complex is implicated in cancers such as myeloid leukemia and small cell lung cancer, making it a therapeutic target.
• Small-molecule inhibitors of METTL3 show efficacy in myeloid leukemia models, highlighting the complex as a druggable target.
• CRISPR-based knockout, knock-in, and overexpression models are essential to dissect the causal roles of individual subunits in disease and development.
Description
The RNA N6-methyladenosine methyltransferase complex (GO:0036396) is a cellular component responsible for the post-transcriptional methylation of adenosine to form N6-methyladenosine (m6A) in RNA. This modification is the most abundant internal mRNA modification in eukaryotes and plays critical roles in RNA metabolism, including stability, splicing, export, and translation. The complex is conserved from yeast to humans, with the budding yeast MIS complex (Mum2p, Ime4p, Slz1p) and the vertebrate METTL3-METTL14-WTAP complex representing the core enzymatic machinery. Understanding this complex is fundamental for researchers studying epitranscriptomics, as it dictates the landscape of m6A deposition and downstream functional outcomes. The m6A writer complex has emerged as a key regulator in development, stem cell differentiation, and disease pathogenesis, particularly in cancer. Its catalytic activity is essential for proper gene expression programs, and its dysregulation is linked to leukemia, lung cancer, and other malignancies. Moreover, the complex interacts with chromatin and splicing factors, suggesting broader roles beyond RNA methylation. This article provides a comprehensive overview of the complex's composition, mechanism, regulation, and the experimental models used to study it, with a focus on CRISPR-based approaches for functional interrogation.
RNA N6-methyladenosine methyltransferase complex At A Glance
| GO ID | GO:0036396 |
|---|---|
| GO term | RNA N6-methyladenosine methyltransferase complex |
| Ontology | cellular_component |
| Synonym | m6A methyltransferase complex; m(6)A writer complex; METTL3-METTL14-WTAP methyltransferase complex; MIS complex; Mum2, Ime4, and Slz1 complex; WMM complex |
| Major function | Catalyzes the methylation of adenosine to N6-methyladenosine (m6A) in RNA |
| Core subunits (vertebrates) | METTL3, METTL14, WTAP |
| Accessory subunits | ZC3H13, VIRMA, CBLL1/HAKAI, RBM15/RBM15B |
| Yeast counterpart | MIS complex (Mum2p, Ime4p, Slz1p) |
| Subcellular localization | Nuclear speckles and chromatin-associated regions |
What Is GO:0036396?
The RNA N6-methyladenosine methyltransferase complex (GO:0036396) is a multi-subunit RNA methyltransferase complex that catalyzes the post-transcriptional methylation of adenosine to form N6-methyladenosine (m6A) in RNA. In budding yeast, the complex is known as the MIS complex and consists of Mum2p, Ime4p, and Slz1p. In vertebrates, the core complex includes the catalytic subunit METTL3, the structural subunit METTL14, and associated components such as WTAP, ZC3H13, VIRMA, CBLL1/HAKAI, and in some cases RBM15 or RBM15B. This complex is also referred to as the m6A writer complex, m(6)A writer complex, METTL3-METTL14-WTAP methyltransferase complex, or WMM complex.
Why Is RNA N6-methyladenosine methyltransferase complex Important in Cell Biology?
The RNA N6-methyladenosine methyltransferase complex is central to epitranscriptomic regulation, as it installs the most prevalent internal RNA modification, m6A, which influences nearly every aspect of RNA life cycle. Its importance spans developmental biology, stem cell maintenance, and disease, particularly cancer, where aberrant m6A deposition drives oncogenesis and therapy resistance. The complex is also a promising therapeutic target, with small-molecule inhibitors showing efficacy in leukemia models. Furthermore, recent evidence indicates that subunits like METTL14 have RNA-independent chromatin regulatory functions, expanding the complex's role beyond RNA methylation. Thus, studying this complex is essential for understanding gene regulation and developing novel interventions.
• Regulates RNA stability, splicing, export, and translation through m6A deposition.
• Essential for embryonic development and stem cell differentiation.
• Implicated in myeloid leukemia; METTL3 inhibition shows therapeutic potential.
• Promotes chemoresistance in small cell lung cancer via mitophagy induction.
• Serves as a biomarker and target in various cancers.
• Subunits like METTL14 have chromatin-associated, RNA-independent functions.
• Conserved from yeast to humans, enabling model organism studies.
• Interacts with splicing factors and chromatin remodelers, linking transcription and RNA modification.
• Small-molecule inhibitors provide chemical tools for functional studies.
• CRISPR screens can identify context-specific dependencies on the complex.
Structure and Composition of RNA N6-methyladenosine methyltransferase complex
Core Enzymatic Subunits: METTL3 and METTL14
In simple terms: METTL3 is the enzyme that does the actual methylation, while METTL14 helps it hold the RNA and choose the right spot.
The catalytic core of the vertebrate m6A writer complex is a heterodimer of METTL3 and METTL14. METTL3 contains the catalytic methyltransferase domain that transfers a methyl group from S-adenosylmethionine (SAM) to the N6 position of adenosine, while METTL14 is catalytically inactive but essential for substrate RNA binding and complex stability. Structural studies reveal that METTL3 and METTL14 form a tight dimer, with the RNA substrate positioned at their interface. This heterodimer is conserved in evolution, with yeast Ime4p and Mum2p serving analogous roles.
Regulatory Subunit WTAP and Accessory Proteins
In simple terms: WTAP acts like a scaffold that holds the core enzymes together and helps them find their targets in the nucleus.
WTAP (Wilms tumor 1-associated protein) is a regulatory subunit that associates with the METTL3-METTL14 heterodimer and is required for its localization to nuclear speckles and for efficient m6A deposition. WTAP also serves as a platform for recruiting additional accessory proteins such as VIRMA (KIAA1429), ZC3H13, CBLL1/HAKAI, and RBM15/RBM15B. These accessory factors contribute to target specificity, complex assembly, and coupling of m6A writing to other RNA processing events. The composition of the complex can vary by cell type and context, with RBM15 or RBM15B present in some cases.
Assembly and Subcellular Localization
In simple terms: The complex assembles in the nucleus and concentrates in speckles, where it modifies RNA as it is being made.
The m6A writer complex assembles in the nucleus and localizes predominantly to nuclear speckles, which are enriched in splicing factors and RNA-processing machinery. Assembly is thought to be initiated by the METTL3-METTL14 heterodimer, followed by WTAP binding and subsequent recruitment of accessory subunits. The complex interacts with the C-terminal domain of RNA polymerase II, coupling m6A deposition to transcription. This spatial and temporal coordination ensures that m6A marks are deposited on nascent RNA transcripts.
Yeast MIS Complex: A Conserved Counterpart
In simple terms: Yeast have a simpler version of the complex called MIS, which does the same basic job with three proteins.
In budding yeast, the m6A writer complex is known as the MIS complex, composed of Mum2p, Ime4p, and Slz1p. Ime4p is the catalytic subunit homologous to METTL3, Mum2p is homologous to METTL14, and Slz1p is a regulatory factor analogous to WTAP. The MIS complex is required for m6A modification during meiosis and is essential for sporulation. Studies in yeast have provided foundational insights into the mechanism and regulation of m6A writing that are conserved in higher eukaryotes.
Key Genes Involved in GO:0036396 RNA N6-methyladenosine methyltransferase complex
The following genes encode the core and accessory subunits of the RNA N6-methyladenosine methyltransferase complex, as well as related regulatory factors.
| Gene | Major Role | Research Relevance |
|---|---|---|
| METTL3 | Catalytic subunit; transfers methyl group to adenosine | Target for small-molecule inhibitors; oncogenic in leukemia and solid tumors |
| METTL14 | Structural subunit; RNA binding and complex stabilization | Chromatin regulation independent of RNA methylation; tumor suppressor or oncogene context-dependent |
| WTAP | Regulatory subunit; scaffold for complex assembly and localization | Essential for m6A deposition; implicated in splicing and cancer |
| ZC3H13 | Accessory subunit; links complex to transcription and splicing | Regulates m6A on specific transcripts; involved in stem cell differentiation |
| VIRMA (KIAA1429) | Accessory subunit; recruits complex to specific RNA regions | Required for m6A near stop codons and 3' UTRs; implicated in cancer |
| CBLL1 (HAKAI) | Accessory subunit; E3 ubiquitin ligase | Couples m6A writing to ubiquitination and RNA processing |
| RBM15 | Accessory subunit; RNA-binding protein | Recruits complex to specific RNAs; involved in hematopoiesis |
| RBM15B | Accessory subunit; RNA-binding protein | Alternative to RBM15; context-dependent m6A targeting |
| METTL3 (yeast Ime4p) | Catalytic subunit in yeast MIS complex | Required for meiosis and sporulation |
| METTL14 (yeast Mum2p) | Structural subunit in yeast MIS complex | Essential for m6A during meiosis |
| WTAP (yeast Slz1p) | Regulatory subunit in yeast MIS complex | Required for sporulation |
| FTO | m6A demethylase (eraser) | Opposes writer complex; linked to obesity and cancer |
| ALKBH5 | m6A demethylase (eraser) | Regulates m6A dynamics; implicated in fertility and cancer |
| YTHDF1/2/3 | m6A reader proteins | Mediate downstream effects on RNA stability and translation |
| IGF2BP1/2/3 | m6A reader proteins | Enhance RNA stability; involved in cancer |
| HNRNPA2B1 | m6A reader | Regulates splicing and miRNA processing |
| eIF3 | m6A reader | Promotes translation initiation on m6A-modified mRNAs |
How Is RNA N6-methyladenosine methyltransferase complex Regulated?
The activity and assembly of the RNA N6-methyladenosine methyltransferase complex are regulated at multiple levels. Expression of core subunits such as METTL3 and METTL14 can be controlled transcriptionally and post-transcriptionally, and their protein stability is influenced by ubiquitination and proteasomal degradation. The complex's localization to nuclear speckles is dependent on WTAP and can be modulated by cellular signals. Additionally, m6A modification itself can feedback on the complex; for example, m6A marks on the transcripts encoding writer components can affect their own stability or translation. Small-molecule inhibitors of METTL3 have been developed and can acutely modulate complex activity, providing chemical tools to study regulation. Furthermore, the complex interacts with chromatin-modifying enzymes, and its recruitment to specific genomic loci may be regulated by transcription factors and chromatin state.
RNA N6-methyladenosine methyltransferase complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| METTL3 | Acute myeloid leukemia; small cell lung cancer chemoresistance | Conditional knockout in hematopoietic stem cells; xenograft models with METTL3 inhibitors |
| METTL14 | AML; glioblastoma; chromatin regulation | Knockout and point-mutation knock-in to separate RNA and chromatin functions |
| WTAP | AML; splicing dysregulation | Knockout in leukemia cell lines; rescue with WTAP mutants |
| VIRMA | Hepatocellular carcinoma; m6A targeting | Liver-specific knockout; RNA-seq and m6A-seq |
| FTO | Obesity; melanoma; AML | Overexpression and knockout models; small-molecule inhibitors |
m6A Writer Complex in Myeloid Leukemia
Dysregulation of the m6A writer complex is a driver of myeloid leukemia. METTL3 is overexpressed in acute myeloid leukemia (AML) and promotes leukemogenesis by methylating key transcripts that sustain oncogenic pathways. Small-molecule inhibition of METTL3 induces differentiation and apoptosis of AML cells and delays leukemia progression in mouse models. These findings establish the complex as a therapeutic target in leukemia and have spurred clinical interest in METTL3 inhibitors.
Role in Small Cell Lung Cancer Chemoresistance
In small cell lung cancer (SCLC), METTL3 promotes chemoresistance by inducing mitophagy, a process that clears damaged mitochondria and protects cancer cells from chemotherapy-induced death. Knockdown of METTL3 sensitizes SCLC cells to chemotherapy, suggesting that targeting the writer complex could overcome resistance. This highlights the complex's role in therapy response and its potential as a combination target.
Broad Implications in Solid Tumors
The m6A writer complex is implicated in numerous solid tumors, including glioblastoma, breast, and liver cancers, where it can act as either an oncogene or tumor suppressor depending on context. METTL3 and METTL14 modulate pathways such as PI3K/AKT, Wnt/β-catenin, and p53, influencing proliferation, metastasis, and stemness. Targeting the complex or its subunits is being explored as a therapeutic strategy across cancer types.
Beyond Cancer: Developmental and Neurological Roles
The m6A writer complex is essential for embryonic development; knockout of Mettl3 or Mettl14 in mice causes early lethality. In the nervous system, m6A modification regulates neurogenesis, synaptic plasticity, and stress responses, and its dysregulation has been linked to neurodevelopmental disorders and neurodegeneration. These roles underscore the complex's broad physiological importance beyond oncology.
From RNA N6-methyladenosine methyltransferase complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the catalytic contribution of METTL3 in a specific cancer? | CRISPR knockout of METTL3 in cancer cell lines, followed by proliferation and m6A-seq |
| Does METTL14 have RNA-independent functions? | Point mutation in METTL14 that abolishes methyltransferase activity, knock-in via CRISPR |
| How does WTAP localization affect m6A deposition? | Tagged knock-in of WTAP with GFP or HA for imaging and immunoprecipitation |
| What is the effect of METTL3 overexpression? | CRISPR activation (CRISPRa) or lentiviral overexpression in cell lines |
| Which transcripts are directly methylated by the complex? | Knockout of core subunits followed by m6A-seq and RNA-seq |
| Can small molecules inhibit the complex in vivo? | Patient-derived xenografts treated with METTL3 inhibitors |
How to Study the RNA N6-methyladenosine methyltransferase complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| m6A-seq (MeRIP-seq) | Transcriptome-wide m6A sites | Mapping m6A changes after knockout or drug treatment |
| RIP-seq / CLIP-seq | RNA binding sites of complex subunits | Identifying direct RNA targets of METTL3 or WTAP |
| Co-IP / mass spectrometry | Protein-protein interactions and complex composition | Discovering new subunits and context-dependent assembly |
| CRISPR knockout screens | Gene essentiality and synthetic lethality | Finding vulnerabilities in cancer cells with writer complex mutations |
| Western blot | Protein expression and post-translational modifications | Validating knockout or overexpression efficiency |
| Immunofluorescence | Subcellular localization of complex subunits | Assessing nuclear speckle localization |
| qRT-PCR | RNA expression levels | Measuring target gene expression after complex perturbation |
| In vitro methyltransferase assay | Enzymatic activity of the complex | Testing small-molecule inhibitors |
m6A Sequencing (m6A-seq) and MeRIP-seq
m6A-seq, also known as MeRIP-seq, combines m6A-specific antibody immunoprecipitation with next-generation sequencing to map m6A sites transcriptome-wide. This method is essential for identifying direct targets of the writer complex and quantifying changes upon knockout or inhibition. It typically requires input RNA and an m6A antibody, followed by peak calling and motif analysis.
RNA Immunoprecipitation (RIP) and CLIP
RIP and CLIP (crosslinking and immunoprecipitation) can identify RNAs bound by individual subunits of the complex, such as METTL3 or WTAP. These techniques provide information on direct RNA-protein interactions and can be combined with sequencing to generate transcriptome-wide binding maps. They are useful for distinguishing subunits' specific RNA targets.
Proteomics and Co-Immunoprecipitation
Co-immunoprecipitation followed by mass spectrometry can identify the composition of the m6A writer complex and its interacting partners in different cell types. This approach has been used to discover accessory subunits like ZC3H13 and VIRMA. It is valuable for understanding context-dependent complex assembly.
CRISPR Screens and Functional Genomics
Genome-wide CRISPR knockout screens can identify genes that are synthetic lethal with m6A writer complex components or that modulate sensitivity to METTL3 inhibitors. Such screens have revealed context-specific dependencies and resistance mechanisms. They are powerful for uncovering novel therapeutic combinations.
How CRISPR Can Be Used to Study GO:0036396 RNA N6-methyladenosine methyltransferase complex
Knockout
CRISPR knockout of core subunits such as METTL3, METTL14, or WTAP is widely used to abolish m6A writer activity and study downstream effects. Knockout cell lines can be generated by introducing indels in early exons, leading to frameshift and loss of protein. These models are essential for validating the complex's role in proliferation, differentiation, and drug response.
Point Mutation
Point mutations can be introduced via CRISPR to dissect specific functions of the complex. For example, a point mutation in the catalytic domain of METTL3 can abolish methyltransferase activity while preserving protein interactions, allowing separation of catalytic and non-catalytic roles. Similarly, mutations in METTL14 can disrupt RNA binding or chromatin association. These models are valuable for understanding structure-function relationships.
Knock-in
Knock-in of tags (e.g., GFP, HA, or FLAG) into endogenous loci using CRISPR enables visualization and immunoprecipitation of complex subunits at physiological levels. Knock-in of disease-associated mutations can model their effects on complex assembly and function. This approach preserves endogenous regulation and is ideal for studying localization and interactions.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression can elevate levels of complex subunits to study gain-of-function effects. Overexpression of METTL3 or METTL14 is common in cancer models to mimic oncogenic upregulation. These models help identify downstream pathways and potential therapeutic vulnerabilities.
How EDITGENE Supports RNA N6-methyladenosine methyltransferase complex Research
Researchers studying RNA N6-methyladenosine methyltransferase complex-related genes often need to determine whether a candidate gene is causally involved in a specific phenotype, such as cancer cell proliferation or drug resistance. This requires precise genetic manipulation to avoid confounding effects from off-target edits or incomplete knockdown. EDITGENE provides a comprehensive suite of CRISPR-based services to generate knockout, point-mutation, knock-in, and overexpression cell models, as well as library screening and bioinformatics support, enabling rigorous functional studies of the m6A writer complex.
Contact EDITGENE today to design your custom CRISPR model for RNA N6-methyladenosine methyltransferase complex research.
Frequently Asked Questions About RNA N6-methyladenosine methyltransferase complex
What is the RNA N6-methyladenosine methyltransferase complex?
It is a multi-subunit protein complex that catalyzes the addition of a methyl group to adenosine in RNA, forming N6-methyladenosine (m6A). It is also known as the m6A writer complex.
What genes are involved in the RNA N6-methyladenosine methyltransferase complex?
Core genes include METTL3, METTL14, and WTAP. Accessory genes include ZC3H13, VIRMA, CBLL1/HAKAI, and RBM15/RBM15B.
What is the function of METTL3 in the m6A writer complex?
METTL3 is the catalytic subunit that transfers a methyl group from SAM to adenosine, forming m6A.
How is the m6A writer complex regulated?
It is regulated by subunit expression, protein stability, localization to nuclear speckles, and interactions with chromatin and splicing factors.
What diseases are associated with the m6A writer complex?
It is implicated in myeloid leukemia, small cell lung cancer, and other cancers, as well as developmental and neurological disorders.
What methods are used to study the m6A writer complex?
Common methods include m6A-seq, RIP-seq, co-immunoprecipitation, CRISPR knockout, and small-molecule inhibition.
Can CRISPR be used to study the m6A writer complex?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect subunit functions.
What is the yeast equivalent of the m6A writer complex?
In budding yeast, it is called the MIS complex, composed of Mum2p, Ime4p, and Slz1p.
Is METTL14 catalytically active?
METTL14 is catalytically inactive but essential for RNA binding and complex stability; it also has RNA-independent chromatin functions.
What are the therapeutic implications of targeting the m6A writer complex?
Small-molecule inhibitors of METTL3 show efficacy in leukemia models, and targeting the complex is being explored in various cancers.
Conclusion
The RNA N6-methyladenosine methyltransferase complex (GO:0036396) is a central player in epitranscriptomic regulation, responsible for depositing m6A on RNA and influencing diverse biological processes. Its core subunits METTL3, METTL14, and WTAP, along with accessory proteins, form a dynamic machinery that is tightly regulated and linked to cancer, development, and neurological disorders. Understanding its structure, mechanism, and regulation is essential for both basic biology and therapeutic development. CRISPR-based models, including knockout, point mutation, knock-in, and overexpression, provide powerful tools to interrogate the complex's functions in health and disease. EDITGENE offers comprehensive services to support these studies, from custom cell line generation to library screening and bioinformatics, enabling researchers to accelerate discoveries in m6A biology.
References
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- 3. Yankova E et al.. 2021. Small-molecule inhibition of METTL3 as a strategy against myeloid leukaemia.. Nature 593(7860):597-601 PMID: 33902106
- 4. Sun Y et al.. 2023. METTL3 promotes chemoresistance in small cell lung cancer by inducing mitophagy.. J Exp Clin Cancer Res 42(1):65 PMID: 36932427
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