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Wiley Interdisciplinary Reviews. RNA Mar 2022The N6-methyladenosine (m6A) RNA methyltransferase METTL16 is an emerging player in the RNA modification landscape of the human cell. Originally thought to be a... (Review)
Review
The N6-methyladenosine (m6A) RNA methyltransferase METTL16 is an emerging player in the RNA modification landscape of the human cell. Originally thought to be a ribosomal RNA methyltransferase, it has now been shown to bind and methylate the MAT2A messenger RNA (mRNA) and U6 small nuclear RNA (snRNA). It has also been shown to bind the MALAT1 long noncoding RNA and several other RNAs. METTL16's methyltransferase domain contains the Rossmann-like fold of class I methyltransferases and uses S-adenosylmethionine (SAM) as the methyl donor. It has an RNA methylation consensus sequence of UACAGARAA (modified A underlined), and structural requirements for its known RNA interactors. In addition to the methyltransferase domain, METTL16 protein has two other RNA binding domains, one of which resides in a vertebrate conserved region, and a putative nuclear localization signal. The role of METTL16 in the cell is still being explored, however evidence suggests it is essential for most cells. This is currently hypothesized to be due to its role in regulating the splicing of MAT2A mRNA in response to cellular SAM levels. However, one of the more pressing questions remaining is what role METTL16's methylation of U6 snRNA plays in splicing and potentially cellular survival. METTL16 also has several other putative coding and noncoding RNA interactors but the definitive methylation status of those RNAs and the role METTL16 plays in their life cycle is yet to be determined. Overall, METTL16 is an intriguing RNA binding protein and methyltransferase whose important functions in the cell are just beginning to be understood. This article is categorized under: RNA Processing > RNA Editing and Modification RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.
Topics: Humans; Methionine Adenosyltransferase; Methylation; Methyltransferases; RNA, Long Noncoding; RNA, Messenger; S-Adenosylmethionine
PubMed: 34227247
DOI: 10.1002/wrna.1681 -
Cell Metabolism Mar 2021Polycystic ovary syndrome (PCOS) is the most common reproductive and metabolic disorder affecting women of reproductive age. PCOS has a strong heritable component, but...
Polycystic ovary syndrome (PCOS) is the most common reproductive and metabolic disorder affecting women of reproductive age. PCOS has a strong heritable component, but its pathogenesis has been unclear. Here, we performed RNA sequencing and genome-wide DNA methylation profiling of ovarian tissue from control and third-generation PCOS-like mice. We found that DNA hypomethylation regulates key genes associated with PCOS and that several of the differentially methylated genes are also altered in blood samples from women with PCOS compared with healthy controls. Based on this insight, we treated the PCOS mouse model with the methyl group donor S-adenosylmethionine and found that it corrected their transcriptomic, neuroendocrine, and metabolic defects. These findings show that the transmission of PCOS traits to future generations occurs via an altered landscape of DNA methylation and propose methylome markers as a possible diagnostic landmark for the condition, while also identifying potential candidates for epigenetic-based therapy.
Topics: Animals; Anti-Mullerian Hormone; Case-Control Studies; DNA Methylation; Disease Models, Animal; Epigenesis, Genetic; Female; Genetic Predisposition to Disease; Humans; Luteinizing Hormone; Male; Mice; Mice, Inbred C57BL; Mixed Function Oxygenases; Ovary; Polycystic Ovary Syndrome; Prenatal Care; Proto-Oncogene Proteins; S-Adenosylmethionine; Transcriptome
PubMed: 33539777
DOI: 10.1016/j.cmet.2021.01.004 -
Cells Jan 2022Alterations of methionine cycle in steatohepatitis, cirrhosis, and hepatocellular carcinoma induce MAT1A decrease and MAT2A increase expressions with the consequent... (Review)
Review
Alterations of methionine cycle in steatohepatitis, cirrhosis, and hepatocellular carcinoma induce MAT1A decrease and MAT2A increase expressions with the consequent decrease of S-adenosyl-L-methionine (SAM). This causes non-alcoholic fatty liver disease (NAFLD). SAM administration antagonizes pathological conditions, including galactosamine, acetaminophen, and ethanol intoxications, characterized by decreased intracellular SAM. Positive therapeutic effects of SAM/vitamin E or SAM/ursodeoxycholic acid in animal models with NAFLD and intrahepatic cholestasis were not confirmed in humans. In in vitro experiments, SAM and betaine potentiate PegIFN-alpha-2a/2b plus ribavirin antiviral effects. SAM plus betaine improves early viral kinetics and increases interferon-stimulated gene expression in patients with viral hepatitis non-responders to pegIFNα/ribavirin. SAM prevents hepatic cirrhosis, induced by CCl4, inhibits experimental tumors growth and is proapoptotic for hepatocellular carcinoma and MCF-7 breast cancer cells. SAM plus Decitabine arrest cancer growth and potentiate doxorubicin effects on breast, head, and neck cancers. Furthermore, SAM enhances the antitumor effect of gemcitabine against pancreatic cancer cells, inhibits growth of human prostate cancer PC-3, colorectal cancer, and osteosarcoma LM-7 and MG-63 cell lines; increases genomic stability of SW480 cells. SAM reduces colorectal cancer progression and inhibits the proliferation of preneoplastic rat liver cells in vivo. The discrepancy between positive results of SAM treatment of experimental tumors and modest effects against human disease may depend on more advanced human disease stage at moment of diagnosis.
Topics: Animals; Antiviral Agents; Betaine; Carcinogenesis; Carcinoma, Hepatocellular; Cell Transformation, Neoplastic; Colorectal Neoplasms; Humans; Liver Neoplasms; Male; Methionine Adenosyltransferase; Non-alcoholic Fatty Liver Disease; Rats; Ribavirin; S-Adenosylmethionine
PubMed: 35159219
DOI: 10.3390/cells11030409 -
The Journal of Clinical Investigation Jul 2023Deciphering the crosstalk between metabolic reprogramming and epigenetic regulation is a promising strategy for cancer therapy. In this study, we discovered that the...
Deciphering the crosstalk between metabolic reprogramming and epigenetic regulation is a promising strategy for cancer therapy. In this study, we discovered that the gluconeogenic enzyme PCK1 fueled the generation of S-adenosylmethionine (SAM) through the serine synthesis pathway. The methyltransferase SUV39H1 catalyzed SAM, which served as a methyl donor to support H3K9me3 modification, leading to the suppression of the oncogene S100A11. Mechanistically, PCK1 deficiency-induced oncogenic activation of S100A11 was due to its interaction with AKT1, which upregulated PI3K/AKT signaling. Intriguingly, the progression of hepatocellular carcinoma (HCC) driven by PCK1 deficiency was suppressed by SAM supplement or S100A11 KO in vivo and in vitro. These findings reveal the availability of the key metabolite SAM as a bridge connecting the gluconeogenic enzyme PCK1 and H3K9 trimethylation in attenuating HCC progression, thus suggesting a potential therapeutic strategy against HCC.
Topics: Humans; Carcinoma, Hepatocellular; S-Adenosylmethionine; Liver Neoplasms; Phosphatidylinositol 3-Kinases; Epigenesis, Genetic; Phosphoenolpyruvate Carboxykinase (GTP); Intracellular Signaling Peptides and Proteins
PubMed: 37166978
DOI: 10.1172/JCI161713 -
Science (New York, N.Y.) Nov 2017mTOR complex 1 (mTORC1) regulates cell growth and metabolism in response to multiple environmental cues. Nutrients signal via the Rag guanosine triphosphatases (GTPases)...
mTOR complex 1 (mTORC1) regulates cell growth and metabolism in response to multiple environmental cues. Nutrients signal via the Rag guanosine triphosphatases (GTPases) to promote the localization of mTORC1 to the lysosomal surface, its site of activation. We identified SAMTOR, a previously uncharacterized protein, which inhibits mTORC1 signaling by interacting with GATOR1, the GTPase activating protein (GAP) for RagA/B. We found that the methyl donor -adenosylmethionine (SAM) disrupts the SAMTOR-GATOR1 complex by binding directly to SAMTOR with a dissociation constant of approximately 7 μM. In cells, methionine starvation reduces SAM levels below this dissociation constant and promotes the association of SAMTOR with GATOR1, thereby inhibiting mTORC1 signaling in a SAMTOR-dependent fashion. Methionine-induced activation of mTORC1 requires the SAM binding capacity of SAMTOR. Thus, SAMTOR is a SAM sensor that links methionine and one-carbon metabolism to mTORC1 signaling.
Topics: HEK293 Cells; Humans; Intracellular Signaling Peptides and Proteins; Lysosomes; Mechanistic Target of Rapamycin Complex 1; Protein Domains; Protein Interaction Maps; S-Adenosylmethionine; Signal Transduction
PubMed: 29123071
DOI: 10.1126/science.aao3265 -
Cell May 2017Maintenance of proper levels of the methyl donor S-adenosylmethionine (SAM) is critical for a wide variety of biological processes. We demonstrate that the N-adenosine...
Maintenance of proper levels of the methyl donor S-adenosylmethionine (SAM) is critical for a wide variety of biological processes. We demonstrate that the N-adenosine methyltransferase METTL16 regulates expression of human MAT2A, which encodes the SAM synthetase expressed in most cells. Upon SAM depletion by methionine starvation, cells induce MAT2A expression by enhanced splicing of a retained intron. Induction requires METTL16 and its methylation substrate, a vertebrate conserved hairpin (hp1) in the MAT2A 3' UTR. Increasing METTL16 occupancy on the MAT2A 3' UTR is sufficient to induce efficient splicing. We propose that, under SAM-limiting conditions, METTL16 occupancy on hp1 increases due to inefficient enzymatic turnover, which promotes MAT2A splicing. We further show that METTL16 is the long-unknown methyltransferase for the U6 spliceosomal small nuclear RNA (snRNA). These observations suggest that the conserved U6 snRNA methyltransferase evolved an additional function in vertebrates to regulate SAM homeostasis.
Topics: Animals; Base Sequence; Gene Expression Regulation, Enzymologic; HEK293 Cells; Humans; Introns; Inverted Repeat Sequences; Methionine Adenosyltransferase; Methylation; Methyltransferases; RNA Splicing; S-Adenosylmethionine; Schizosaccharomyces
PubMed: 28525753
DOI: 10.1016/j.cell.2017.05.003 -
Cell Metabolism Aug 2023There has been an intense focus to uncover the molecular mechanisms by which fasting triggers the adaptive cellular responses in the major organs of the body. Here, we...
There has been an intense focus to uncover the molecular mechanisms by which fasting triggers the adaptive cellular responses in the major organs of the body. Here, we show that in mice, hepatic S-adenosylmethionine (SAMe)-the principal methyl donor-acts as a metabolic sensor of nutrition to fine-tune the catabolic-fasting response by modulating phosphatidylethanolamine N-methyltransferase (PEMT) activity, endoplasmic reticulum-mitochondria contacts, β-oxidation, and ATP production in the liver, together with FGF21-mediated lipolysis and thermogenesis in adipose tissues. Notably, we show that glucagon induces the expression of the hepatic SAMe-synthesizing enzyme methionine adenosyltransferase α1 (MAT1A), which translocates to mitochondria-associated membranes. This leads to the production of this metabolite at these sites, which acts as a brake to prevent excessive β-oxidation and mitochondrial ATP synthesis and thereby endoplasmic reticulum stress and liver injury. This work provides important insights into the previously undescribed function of SAMe as a new arm of the metabolic adaptation to fasting.
Topics: Mice; Animals; S-Adenosylmethionine; Liver; Liver Neoplasms; Fasting; Adenosine Triphosphate; Methionine Adenosyltransferase; Phosphatidylethanolamine N-Methyltransferase
PubMed: 37527658
DOI: 10.1016/j.cmet.2023.07.002 -
Nature Biotechnology Jun 2019RNA aptamers and RNA aptamer-based devices can be genetically encoded and expressed in cells to probe and manipulate cellular function. However, their usefulness in the...
RNA aptamers and RNA aptamer-based devices can be genetically encoded and expressed in cells to probe and manipulate cellular function. However, their usefulness in the mammalian cell is limited by low expression and rapid degradation. Here we describe the Tornado (Twister-optimized RNA for durable overexpression) expression system for achieving rapid RNA circularization, resulting in RNA aptamers with high stability and expression levels. Tornado-expressed transcripts contain an RNA of interest flanked by Twister ribozymes. The ribozymes rapidly undergo autocatalytic cleavage, leaving termini that are ligated by the ubiquitous endogenous RNA ligase RtcB. Using this approach, protein-binding aptamers that otherwise have minimal effects in cells become potent inhibitors of cellular signaling. Additionally, an RNA-based fluorescent metabolite biosensor for S-adenosyl methionine (SAM) that is expressed at low levels when expressed as a linear RNA achieves levels sufficient for detection of intracellular SAM dynamics when expressed as a circular RNA. The Tornado expression system thus markedly enhances the utility of RNA-based approaches in the mammalian cell.
Topics: Aptamers, Nucleotide; Catalysis; Gene Expression Regulation; Ligases; Nucleic Acid Conformation; RNA; RNA, Catalytic; RNA, Circular; S-Adenosylmethionine
PubMed: 30962542
DOI: 10.1038/s41587-019-0090-6 -
Chembiochem : a European Journal of... Sep 2022In this review the current state-of-the-art of S-adenosylmethionine (SAM)-dependent methyltransferases and SAM are evaluated. Their structural classification and... (Review)
Review
In this review the current state-of-the-art of S-adenosylmethionine (SAM)-dependent methyltransferases and SAM are evaluated. Their structural classification and diversity is introduced and key mechanistic aspects presented which are then detailed further. Then, catalytic SAM as a target for drugs, and approaches to utilise SAM as a cofactor in synthesis are introduced with different supply and regeneration approaches evaluated. The use of SAM analogues are also described. Finally O-, N-, C- and S-MTs, their synthetic applications and potential for compound diversification is given.
Topics: Methyltransferases; S-Adenosylmethionine
PubMed: 35691829
DOI: 10.1002/cbic.202200212 -
Blood Nov 2022Targeting altered tumor cell metabolism might provide an attractive opportunity for patients with acute myeloid leukemia (AML). An amino acid dropout screen on primary...
Targeting altered tumor cell metabolism might provide an attractive opportunity for patients with acute myeloid leukemia (AML). An amino acid dropout screen on primary leukemic stem cells and progenitor populations revealed a number of amino acid dependencies, of which methionine was one of the strongest. By using various metabolite rescue experiments, nuclear magnetic resonance-based metabolite quantifications and 13C-tracing, polysomal profiling, and chromatin immunoprecipitation sequencing, we identified that methionine is used predominantly for protein translation and to provide methyl groups to histones via S-adenosylmethionine for epigenetic marking. H3K36me3 was consistently the most heavily impacted mark following loss of methionine. Methionine depletion also reduced total RNA levels, enhanced apoptosis, and induced a cell cycle block. Reactive oxygen species levels were not increased following methionine depletion, and replacement of methionine with glutathione or N-acetylcysteine could not rescue phenotypes, excluding a role for methionine in controlling redox balance control in AML. Although considered to be an essential amino acid, methionine can be recycled from homocysteine. We uncovered that this is primarily performed by the enzyme methionine synthase and only when methionine availability becomes limiting. In vivo, dietary methionine starvation was not only tolerated by mice, but also significantly delayed both cell line and patient-derived AML progression. Finally, we show that inhibition of the H3K36-specific methyltransferase SETD2 phenocopies much of the cytotoxic effects of methionine depletion, providing a more targeted therapeutic approach. In conclusion, we show that methionine depletion is a vulnerability in AML that can be exploited therapeutically, and we provide mechanistic insight into how cells metabolize and recycle methionine.
Topics: Mice; Animals; Methionine; Leukemia, Myeloid, Acute; S-Adenosylmethionine; Histones; Racemethionine
PubMed: 35984907
DOI: 10.1182/blood.2022017575