N6-methyladenosine, abbreviated m6A, is a small chemical tag added to RNA after it has been copied from DNA. It is the most common internal modification found on messenger RNA in plants, animals, and other complex organisms, and it influences nearly every stage of an RNA molecule’s life: how it is spliced, where it travels inside the cell, how efficiently it gets translated into protein, and when it is destroyed.1PubMed Central. A Review in Research Progress Concerning m6A Methylation and Immunoregulation Despite being discovered in the 1970s, m6A spent decades in relative obscurity before a surge of research beginning around 2011 revealed that the mark is reversible and tightly regulated, making it far more dynamic than anyone had assumed.
What m6A Actually Is
The “m6A” name describes the chemistry: a methyl group (a carbon atom bonded to three hydrogens) gets attached to the nitrogen at position 6 of adenosine, one of the four building blocks of RNA. This tiny addition does not change the genetic code carried by the RNA molecule. Instead, it changes the molecule’s shape and surface just enough to alter how proteins interact with it. Think of it as a Post-it note stuck to a specific page in a long instruction manual. The words on the page remain the same, but the Post-it tells cellular machinery to treat that page differently.
The modification is conserved across a wide range of species, from yeast and plants to insects and mammals, which suggests it plays fundamental roles that natural selection has maintained over hundreds of millions of years.2Signal Transduction and Targeted Therapy. The role of m6A modification in the biological functions and diseases In a typical human cell, thousands of RNA molecules carry at least one m6A mark, and many carry several. The marks tend to cluster near stop codons and in long internal stretches of the RNA, following a preferred sequence motif.
Writers, Erasers, and Readers
The field describes the proteins involved in m6A biology with a memorable shorthand. “Writers” install the mark. “Erasers” remove it. “Readers” recognize it and carry out downstream effects. This three-part system is what makes m6A reversible and responsive to changing conditions, rather than a permanent stamp applied once and forgotten.
The main writer is a protein complex anchored by two partners called METTL3 and METTL14. Structural work has shown that METTL3 is the catalytically active partner, the one that actually transfers the methyl group, while METTL14 plays a supporting role in recognizing the target RNA and stabilizing the complex.3Molecular Cell. Structural Basis for Cooperative Function of Mettl3 and Mettl14 Methyltransferases Additional proteins help guide the complex to the right spots on RNA, but METTL3 and METTL14 are the core engine.
Two erasers handle removal: FTO and ALKBH5. Both are oxidative enzymes, but they work differently. ALKBH5 strips the methyl group off in a single step, converting the modified base directly back to ordinary adenosine. FTO takes a more roundabout path, first converting m6A to an intermediate form before eventually releasing the methyl group.4PubMed Central. Distinct RNA N-demethylation pathways catalyzed by nonheme iron ALKBH5 and FTO enzymes enable regulation of formaldehyde release rates The existence of two erasers with distinct chemistry hints that cells need fine-grained control over where, when, and how quickly m6A marks are removed.5PubMed Central. Insights into the m6A demethylases FTO and ALKBH5: structural, biological function, and inhibitor development
The readers are a more diverse cast. The best-studied belong to the YTH domain family, a group of proteins whose shared structural pocket fits snugly around m6A-marked RNA. Other reader families, including certain heterogeneous nuclear ribonucleoproteins and insulin-like growth factor 2 mRNA-binding proteins, also recognize m6A and funnel the marked transcript toward different fates.6PubMed Central. m6A-binding proteins: the emerging crucial performers in epigenetics Which reader gets there first effectively decides the RNA’s destiny.
How m6A Shapes RNA Fate
Once an m6A mark is in place and a reader protein latches onto it, the downstream effects vary depending on which reader is involved and where in the cell the encounter happens. Several major outcomes have been mapped in detail.
Splicing
Before a messenger RNA leaves the nucleus, it gets edited: certain segments are cut out and the remaining pieces are stitched together. This process, called splicing, can produce different protein variants from the same gene depending on which segments are kept. The nuclear reader YTHDC1 uses m6A marks to steer splicing decisions, promoting the inclusion of certain segments by recruiting one splicing factor while blocking a competing one.7PubMed. Nuclear m6A Reader YTHDC1 Regulates mRNA Splicing Work in mouse egg cells confirmed that the majority of splicing defects caused by removing YTHDC1 could be rescued by restoring a functional copy of the protein, but not by a version unable to bind m6A, linking the effect directly to the modification itself.8PLoS Genetics. Nuclear m6A reader YTHDC1 regulates alternative polyadenylation and splicing during mouse oocyte development
Stability and Degradation
Many m6A-marked transcripts have shorter lifespans than their unmarked counterparts. The reader YTHDF2 is a key player here: it binds m6A-containing RNA and directs it toward degradation machinery, effectively putting an expiration date on the message.9PubMed Central. Understanding YTHDF2-mediated mRNA Degradation By m6A-BERT-Deg This gives cells a way to rapidly clear out transcripts they no longer need, for example during a shift from one developmental program to another.
Phase Separation and Stress Granules
One of the more surprising discoveries of recent years is that m6A influences the physical organization of the cell’s interior. When an RNA molecule carries multiple m6A marks, it can act as a scaffold that brings YTHDF proteins together. Those proteins in turn cluster through their flexible, disordered tails, causing the RNA-protein mixture to condense into droplet-like compartments through a process called phase separation.10PubMed Central. m6A enhances the phase separation potential of mRNA Under stress, this same principle helps assemble stress granules, temporary storage depots where the cell parks mRNAs it does not want to translate until conditions improve. YTHDF proteins lower the energy barrier for stress granule formation, making it easier for the granules to coalesce.11bioRxiv. m6A-binding YTHDF proteins promote stress granule formation by modulating phase separation of stress granule proteins
Stem Cells and Early Development
Embryonic stem cells can become virtually any cell type in the body, but they need to shut down their self-renewal program before they can commit to a specific identity. m6A plays a gatekeeping role in that transition. When METTL3 is genetically removed or depleted in mouse and human embryonic stem cells, certain self-renewal genes, including the key pluripotency factor Nanog, keep being expressed longer than they should. The cells get stuck in a state of indecision, struggling to exit self-renewal and differentiate into specific lineages.12PubMed Central. m6A RNA modification controls cell fate transition in mammalian embryonic stem cells In other words, m6A marks act as a kind of clearance tag on the transcripts that maintain stemness, ensuring those messages get degraded on schedule so differentiation can proceed.13Genes & Diseases. The regulatory role of m6A modification in the maintenance and differentiation of embryonic stem cells
Memory, Synapses, and the Aging Brain
The brain is one of the most metabolically active organs, constantly remodeling its connections in response to experience. That remodeling depends on rapid, localized production of new proteins at synapses, and m6A appears to be part of the control system governing that production. Research in aging mice and in tissue from Alzheimer’s disease patients found that m6A levels drop on transcripts encoding key synaptic proteins, particularly those involved in signaling at the junctions between neurons. The decline in m6A correlated with reduced local protein synthesis and impaired synaptic function.14PubMed Central. Conserved reduction of m6A RNA modifications during aging and neurodegeneration is linked to changes in synaptic transcripts
Pharmacological experiments have pushed this further. A potent inhibitor of METTL3 called STM2457, when applied to rat brain tissue, blocked long-term potentiation, a form of synaptic strengthening widely considered the cellular basis of memory, without affecting baseline transmission. Conversely, inducing long-term potentiation in living animals raised m6A levels at the activated synapses, suggesting that the modification is both required for and triggered by the strengthening process.15PubMed. Drugs targeting synaptic RNA m6A methylation regulate synaptic transmission and plasticity in the rat hippocampus These findings raise the possibility that age-related or disease-related erosion of m6A could contribute to cognitive decline, though much remains to be tested in clinical settings.
Cancer Connections
Because m6A controls the stability and translation of so many transcripts, disruptions to the system can have outsized effects on cell growth and survival. In acute myeloid leukemia, both the writing and erasing sides of the equation have been implicated. METTL3 and METTL14 are highly expressed in most subtypes of the disease, and their overexpression promotes cell proliferation and blocks the normal cell-death pathways. Knockdown experiments in leukemia cell lines showed that reducing METTL3 or METTL14 inhibited growth and pushed cells toward differentiation and death, with the effect traced to a signaling pathway that controls the tumor suppressor p53.16PubMed Central. The m6A RNA methyltransferase METTL3/METTL14 promotes leukemogenesis through the mdm2/p53 pathway in acute myeloid leukemia
On the eraser side, ALKBH5 is overexpressed in a specific leukemia subtype defined by a chromosomal rearrangement. Silencing ALKBH5 in patient-derived cells suppressed proliferation and induced cell death, with the mechanism traced to a target transcript whose stability depends on the removal of m6A marks by ALKBH5.17PubMed Central. RNA demethylase ALKBH5 promotes tumorigenesis of t(8;21) acute myeloid leukemia via ITPA m6A modification The picture that emerges is that cancer cells can hijack either the writing or the erasing machinery, depending on which transcripts they need to stabilize or destabilize to keep growing.
Viral Infections and Immune Evasion
Cells face a constant challenge in distinguishing their own RNA from foreign material introduced by viruses. m6A has emerged as one of the markers cells use for this purpose, essentially as an evolutionary tag of “self.” Viral RNA that lacks m6A modifications is more likely to form double-stranded structures that trigger innate immune sensors.18PubMed Central. m6A Methylation in Regulation of Antiviral Innate Immunity
Some viruses have evolved a countermeasure. When cells are infected by certain RNA viruses, METTL3 can relocate from the nucleus to the cytoplasm and add m6A marks to viral transcripts. This reduces the formation of double-stranded viral RNA, making it harder for immune sensors to detect the invader and dampening the antiviral response.19Nature Communications. N6-methyladenosine RNA modification suppresses antiviral innate sensing pathways via reshaping double-stranded RNA The virus, in effect, co-opts the cell’s own marking system to fly under the radar. This finding has implications for vaccine design and antiviral therapy, because manipulating the m6A status of therapeutic RNA molecules could potentially tune how strongly the immune system responds to them.
Beyond Messenger RNA
Although most research attention has focused on m6A in messenger RNA, the modification also appears on other RNA species. Long non-coding RNAs, microRNAs, and circular RNAs all carry m6A marks, and a growing body of work points to functional crosstalk between m6A and these non-coding molecules.20Molecular Therapy Nucleic Acids. Interplay between N6-methyladenosine (m6A) and non-coding RNAs in cancer For instance, m6A on a primary microRNA transcript can influence how efficiently that microRNA is processed, which in turn affects the stability of hundreds of downstream target mRNAs. The scope of m6A’s influence is broader than early studies suggested, and the full inventory of affected RNA types is still being filled in.
Crosstalk With DNA and Histone Modifications
Cells regulate gene expression at multiple levels: chemical marks on DNA itself, modifications to the histone proteins that DNA wraps around, and now the m6A marks on RNA. These layers do not operate in isolation. A growing body of evidence shows that m6A and histone modifications influence each other in a bidirectional conversation. Certain histone marks can recruit the m6A writer complex to specific stretches of RNA as they are being transcribed, essentially telling the cell “mark the RNA being made from this gene.”21PubMed Central. Crosstalk Between Histone and m6A Modifications and Emerging Roles of m6A RNA Methylation Conversely, m6A-marked RNAs can recruit chromatin-modifying enzymes back to the genome, creating feedback loops between RNA modifications and the chromatin landscape.22PubMed. Crosstalk between histone/DNA modifications and RNA N6-methyladenosine modification The implication is that m6A is not just a post-transcriptional afterthought but is woven into the broader regulatory architecture that determines which genes are active and how vigorously they are expressed.
Plant Biology and Agriculture
m6A is not exclusively an animal phenomenon. Plants rely on the same core writer and eraser proteins, and the modification regulates processes spanning embryo development, organ formation, flowering time, fruit ripening, and leaf aging.23PubMed Central. Dual Roles of m6A Modification: Orchestrating Development and Abiotic Stress Resilience in Plants Strikingly, when researchers expressed the human FTO eraser protein in rice and potato to broadly remove m6A marks, the plants showed dramatic increases in yield, suggesting that fine-tuning m6A levels could be a practical strategy for crop improvement.24PubMed Central. m6A-mediated regulation of crop development and stress responses
An evolutionary analysis across 13 plant species found that genes shared across distantly related plants tend to carry more m6A marks than species-specific genes, and that the proportion of genes marked with m6A increases with evolutionary age.25Oxford Academic. Evolutionary Implications of the RNA N6-Methyladenosine Methylome in Plants This pattern suggests that m6A regulation has been layered onto genes that perform ancient, conserved functions, consistent with a deep evolutionary role rather than something acquired recently.
The Challenge of Measuring m6A Accurately
One reason the field took so long to gain momentum is that detecting m6A is technically difficult. Early methods relied on antibodies that bind m6A-containing RNA, allowing researchers to pull down marked fragments and sequence them. These approaches can tell you roughly where m6A occurs across the genome’s worth of RNA, but they tend to treat the modification as a binary present-or-absent signal and miss the fact that any given site may be methylated on only a fraction of copies of that transcript at any given moment.26PubMed Central. Stoichiometry-preserving and stochasticity-aware identification of m6A from direct RNA sequencing That loss of quantitative resolution can obscure biologically meaningful variation.
Newer approaches use nanopore sequencing, which threads a single RNA molecule through a tiny pore and reads its sequence in real time. Because the electrical signal changes when a modified base passes through the pore, the method can in principle detect m6A without any chemical treatment. A systematic comparison of ten computational tools for calling m6A from nanopore data found that most present a trade-off between correctly identifying true m6A sites and avoiding false positives, with no single tool dominating on both counts. Combining results from multiple tools substantially improved performance.27Nature Communications. Systematic comparison of tools used for m6A mapping from nanopore direct RNA sequencing The technology is improving quickly, but researchers still need to be cautious about taking any single m6A map at face value.
Drugs Targeting the m6A System
The fact that the m6A machinery is druggable has attracted intense pharmaceutical interest. Because cancers often depend on aberrant m6A writing or erasing to sustain growth, small molecules that block these enzymes could, in theory, cut off the tumor’s supply of pro-survival transcripts.28PubMed Central. Small molecule inhibitors targeting m6A regulators The most advanced candidate is STC-15, a METTL3 inhibitor that has entered early-phase clinical testing in cancer patients, making it the first drug of its kind to reach that milestone.29PubMed. Small-Molecule Inhibitors Targeting RNA m6A Modifiers for Cancer Therapeutics: Latest Advances and Future Perspectives
Beyond oncology, the same pharmacological toolkit has begun to prove useful as a research probe. The METTL3 inhibitor STM2457, for example, was used in the synaptic plasticity experiments described earlier to demonstrate that m6A writing is required for long-term potentiation in the hippocampus.30PubMed. Drugs targeting synaptic RNA m6A methylation regulate synaptic transmission and plasticity in the rat hippocampus Whether such compounds could eventually be repurposed for neurodegenerative conditions remains speculative, but the proof of concept that m6A enzymes can be selectively blocked in living tissue has opened a door that was firmly closed a decade ago. Work on eraser inhibitors is also advancing, with several FTO- and ALKBH5-targeting molecules in preclinical development.31PubMed Central. Insights into the m6A demethylases FTO and ALKBH5: structural, biological function, and inhibitor development The challenge for all of these programs will be achieving enough selectivity to hit the intended enzyme in tumor or brain tissue without disrupting m6A regulation in healthy cells, a problem shared with many epigenetic therapies.