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ObjectiveTo explore the effect and mechanism of Sishenwan-containing serum on aerobic glycolysis in human colon cancer HCT116 cells. MethodCell counting kit-8 （CCK-8） was used to detect the cell viability of colon cancer HCT116 cells after treatment with Sishenwan-containing serum （2.5%， 5%， and 10%） for 24， 48， 72 h. The concentration of lactic acid， the content of intracellular glucose， and the activity of hexokinase （HK） and fructose-6-phosphate kinase （PFK） in the cell culture medium were detected by the micro-method. The content of glucose transporter 1 （GluT1） mRNA was detected by Real-time quantitative polymerase chain reaction （Real-time PCR）. The protein expression of GluT1 and methyltransferase-like 3 （MettL3） was detected by Western blot. The expression of GluT1 in cells was detected by immunofluorescence and the level of N6-methyladenosine （m6A） RNA methylation was detected by colorimetry. ResultCompared with the normal serum， 2.5%， 5%， and 10% Sishenwan-containing serum had no significant effect on the viability of HCT116 cells at 24 h， while 10% Sishenwan-containing serum showed a significant inhibitory effect on the viability of HCT116 cells at 48 h （P<0.05）. Hence， 10% Sishenwan-containing serum was used in subsequent experiments， and the intervention time was 48 h. Compared with the normal serum， 10% Sishenwan-containing serum could reduce lactate production （P<0.05）， down-regulate glucose uptake （P<0.05）， and blunt the activities of HK and PFK， the key rate-limiting enzymes of glycolysis （P<0.05）. Meanwhile， 10% Sishenwan-containing serum could decrease the expression of GluT1 protein （P<0.01） and mRNA （P<0.05） and reduce the proportion of cells expressing GluT1 （P<0.01）. Compared with the normal serum， Sishenwan-containing serum also decreased the protein content of MettL3 （P<0.05） and the methylation level of m6A RNA （P<0.01）. ConclusionSishenwan can inhibit glycolysis in colon cancer cells， and its inhibitory mechanism may be related to reducing MettL3 overexpression， inhibiting m6A RNA methylation， and down-regulating GluT1 and the activities of intracellular aerobic glycolysis-related enzymes such as HK and PFK.
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In non-small cell lung cancer(NSCLC),the heterogeneity promotes drug resistance,and the restricted expression of programmed death-ligand 1(PD-L1)limits the immunotherapy benefits.Based on the mechanisms related to translation regulation and the association with PD-L1 of methyltransferase-like 3(METTL3),the novel small-molecule inhibitor STM2457 is assumed to be useful for the treat-ment of NSCLC.We evaluated the efficacy of STM2457 in vivo and in vitro and confirmed the effects of its inhibition on disease progression.Next,we explored the effect of STM2457 on METTL3 and revealed its effects on the inhibition of catalytic activity and upregulation of METTL3 protein expression.Importantly,we described the genome-wide characteristics of multiple omics data ac-quired from RNA sequencing,ribosome profiling,and methylated RNA immunoprecipitation sequencing data under STM2457 treatment or METTL3 knockout.We also constructed a model for the regulation of the translation of METTL3 and PD-L1.Finally,we found PD-Ll upregulation by STM2457 in vivo and in vitro.In conclusion,STM2457 is a potential novel suppressor based on its inhibitory effect on tumor progression and may be able to overcome the heterogeneity based on its impact on the translatome.Furthermore,it can improve the immunotherapy outcomes based on PD-L1 upregulation in NSCLC.
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AIM: To investigate the role and mechanism of N6-methyladenosine(m6A)methyltransferase 3(METTL3)in the pathogenesis of diabetic cataract.METHODS: We cultured SRA01/04 cells in low and high sugar media for 24h and measured changes in epithelial-mesenchymal transition(EMT)indicators(E-Cadherin, N-Cadherin, ZO-1 and α-SMA)using RT-qPCR and Western blot assays. Cell migration was also assessed using transwell and scratch assays. To investigate the expression level and localization of METTL3 in human lens anterior capsules tissues. Additionally, we used m6A dot blot assay to detect the m6A methylation level of cells cultured in low and high glucose media for 24h, and employed RT-qPCR and Western blot experiments to detect RNA and protein expression of METTL3 in cells. We then treated the cells with METTL3 inhibitor and measured changes in EMT markers by RT-qPCR and Western blot; m6A methylation level was detected by m6A dot blot test; cell migration was detected by Transwell. Finally, the expression of transforming growth factor-β(TGFβ1)in cultured cells was assessed by immunofluorescence staining and the expression levels of TGFβ1 and SNAIL in cells were determined using RT-qPCR and Western blot.RESULTS: Under high glucose conditions, the expression of EMT markers, METTL3, and m6A methylation levels were significantly increased in cells(P<0.05). Furthermore, the migratory ability of cells was higher in high-sugar medium than in low-sugar medium. In human lens anterior capsules, METTL3 expression was higher in patients with diabetic cataract compared to those with age-related cataract. Importantly, treatment with the METTL3 inhibitor STM2457 inhibited EMT in cells, the expression of TGFβ1 and SNAIL, as well as m6A methylation levels in cells(all P<0.05)compared to high-sugar + dimethyl sulfoxide(DMSO)group. Moreover, the migratory capacity of cells was reduced after the addition of STM2457 compared to the high-sugar + DMSO group.CONCLUSION:METTL3 promotes the EMT in human lens epithelial cells under high glucose conditions by activating the TGFβ1/SNAIL pathway, thus contributing to the development of diabetic cataracts.
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AIM: To investigate the role and mechanism of methyltransferase-like 3(METTL3)-mediated N6-methyladenosine(m6A)methylation modification in regulating biological activity of vascular endothelial cells in the pathogenesis of choroidal neovascularization.METHODS: Human umbilical vein endothelial cells(HUVEC)cultured in vitro were divided into the following groups: control group(normal culture), low density lipoprotein(LDL)group, fluorescence-labelled LDL(Dil-LDL)group, 12.5μg/mL and 25μg/mL oxidized LDL(ox-LDL)groups, 12.5μg/mL and 25μg/mL fluorescence-labelled ox-LDL(Dil-ox-LDL)groups, DMSO group, STM2457(METTL3 inhibitor)group, DAPT group; and monkey retina-choroidal endothelial cells(RF/6A)cultured in vitro were divided into control group, DMSO group, 12.5 μg/mL ox-LDL group, and DAPT group. Endocytosed lipoprotein level was examined through fluorescence microscopy. RNA m6A methylation level was detected through a dot blot assay. Protein and RNA levels of METTL3 or angiogenesis-related markers were measured through Western blot assays and real-time quantitative polymerase chain reaction(RT-qPCR), respectively. METTL3 expression and localization were investigated through immunofluorescence. Cell migratory and tube formation capacities were assessed through transwell migration and tube formation assays, respectively.RESULTS: Endocytosed lipoprotein levels in HUVECs exposed to Dil-LDL, 12.5μg/mL and 25μg/mL Dil-ox-LDL groups were significantly higher than those in the control group. 12.5μg/mL and 25μg/mL ox-LDL groups significantly increased m6A methylation(all P<0.05), METTL3 protein expression(all P<0.01), and cell migration and angiogenesis capacities(all P<0.01). METTL3 mRNA level was significantly unregulated in the 12.5μg/mL ox-LDL group(P<0.05). In comparison to the DMSO group, the addition of STM2457 caused significant decrease in m6A methylation level(P<0.05), expression of VEGF and other angiogenesis-related markers(all P<0.05), cell migration and angiogenesis capacities(all P<0.01)and the expression of NICD(P<0.05). However, there were no significant differences in METTL3 protein and mRNA levels(all P>0.05). The expression of VEGF and NICD(all P<0.05), as well as the ability of cell migration and angiogenesis of RF/6A, was all significantly decreased in the DAPT group compared to the DMSO group(all P<0.01).CONCLUSION: METTL3-mediated m6A methylation modification promotes angiogenesis in vascular endothelial cells via the Notch signaling pathway in the pathogenesis of choroidal neovascularization.
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Bladder cancer (BCa) is one of the most common cancers in urology,whose pathogenesis is still unclear. Methyltransferase-like 3(METTL3) is the most important part of N6-methyladenosine methyltransferase complex (m6A MTC),which mediates the methylation of mRNA to regulate the stability and translation process of mRNA. Researches have shown that METTL3 can promote BCa development via AFF4/NF-κB/MYC signaling network,which involves many kinds of signaling molecules. In addition,METTL3 can affect the expressions of AFF4,NF-κB and MYC,so as to affect their downstream signaling pathways and finally promote the malignant progression of tumor.
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Objective:To investigate the role and mechanism of N 6-methyladenosine (m 6A) methyltransferase-like 3 (METTL3) in vascular calcification (VC) of chronic kidney disease (CKD) through apoptosis-associated protein. Methods:(1) Real-time fluorescence quantitative PCR was used to test METTL3 mRNA in serum of maintenance hemodialysis (MHD) patients. (2) Western blotting was used to detect the expression of METTL3 protein in high-phosphorus stimulated vascular smooth muscle cells (VSMCs), and immunofluorescence double lable was used to observe the distribution of METTL3 and Runt-related transcription factor 2 (Runx2). The METTL3 overexpressed and knockdown plasmids were constructed and transfected into VSMCs. Alizarin red staining was used to detect calcification degree. Western blotting was used to detect the expressions of osteogenic markers [Runx2, bone morphogenetic protein-2(BMP-2), collagen Ⅰ] and apoptosis- related proteins Bax and Bcl-2. (3) SD rats were randomly divided into control group, CKD-VC group and S-adenosylhomocysteine (SAH) intervention group. The calcification of thoracic aorta was evaluated by von Kossa staining, and the protein expressions of Runx2, Bax and Bcl-2 were detected by immunohistochemistry and Western blotting.Results:(1) METTL3 mRNA expression in MHD patients with VC was significantly lower than that in non-VC patients ( P<0.05), and was negatively correlated with coronary artery calcium score ( r=-0.65, P<0.001). (2) The expression of METTL3 in VSMCs stimulated by high phosphorus was decreased and showed a time dependence. Immunofluorescence double label showed that METTL3 and Runx2 were co-expressed in the nucleus. METTL3 was overexpressed in high-phosphorus induced VSMCs, and the expressions of Runx2, collagen I and BMP-2 were significantly decreased, accompanied by the decrease of calcified nodules and Bax/Bcl-2 ratio (all P<0.05). Conversely, METTL3 knockdown aggravated VSMCs calcification by inducing apoptosis. (3) Furthermore, METTL3 inhibitor SAH was administered in vivo, and it was found that inhibition of METTL3 expression significantly increased the calcification of rat thoracic aorta, and the Bax/Bcl-2 ratio and Runx2 expression were up-regulated. Conclusions:Serum METTL3 level is reduced in MHD patients with VC. In vivo and in vitro studies demonstrate that METTL3 inhibits VC in CKD by mediating the apoptosis-related protein Bax/Bcl-2.
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Objective:To explore the role of N 6-methyladenosine (m6A) and its regulator METTL3 in the non-coding RNA of endometrial cancer.Methods:The expression levels of m6A and METTL3 were quantified in 20 paired carcinoma and adjacent clinical tissue samples from patients at from Jul. 2016 to Dec. 2020. HEC-1-A cell lines were constructed with METTL3 overexpression and knockdown. Western blot was used to detect the phosphorylation levels of key molecules in METTL3 and Akt/mTOR. The quantitative detection of mRNA levels were used qRT-PCR. The binding level of m6A to its receptor DGCR8 was determined by RNA immunoprecipitation.Results:The results of the m6A RNA methylation quantification kit showed that m6A (1.0±0.15) vs (1.7±0.34) ( P<0.01) and METTL3 levels were elevated in endometrial cancer cells, and METTL3 (1.0±0.13) vs (2.5±0.45) ( P<0.05) levels were elevated in endometrial cancer cells. Western blot and qRT-PCR detection of miR-17-92 cell clusters overexpressing METTL3, METTL3 overexpression significantly increased m6A modification on pri-miR-17-92 ( P<0.05) . Phosphorylation levels of AKT/mTOR pathway-related proteins were upregulated. In addition, RIP test results indicated that the binding of DGCR8 to pri-miR-17-92 was significantly facilitated. Conclusion:METTL3 modification of m6A facilitates the processing of pri-miR-1792 into the miR-17-92 clusters via m6A/DGCR8-dependent mechanism, which in turn activated the AKT/mTOR pathway.
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SUMMARY: The Mettl3/Mettl14 methyltransferase complex installs the most ubiquitous internal mRNA modification- N6-methyladenosine (m6A). The vertebrate retina development is a multi-step process that requires fine-tuning of multiple cellular events, but very little is known about the potential function of Mettl3 and Mettl14 in this process. In this study, we demonstrated the spatio-temporal expression of Mettl3 and Mettl14 during retina development in mouse by quantitative PCR and immunofluorescence staining. We found that these two components of methyltransferase complex could be detected from the beginning of retina development; and the expression of Mettl3 and Mettl14 were gradually restricted to inner nuclear layer (INL) and ganglion cell layer (GCL); Double labeling showed that Mettl3 and Mettl14 had similar expression patterns in mature retinal INL and GCL. Overall, our spatio-temporal expression data provided the foundation for future research on the function of m6A modification in the retina development.
RESUMEN: El complejo Mettl3 / Mettl14 metiltransferasa establece la modificación interna más significativa de ARNm: N6- metiladenosina (m6A). El desarrollo de la retina de los vertebrados es un proceso de varios pasos que requiere múltiples eventos celulares; existe muy poca información sobre la función potencial de Mettl3 y Mettl14 en este proceso. En este estudio, demostramos la expresión espacio-temporal de Mettl3 y Mettl14 durante el desarrollo de la retina en ratón mediante PCR cuantitativa y tinción de inmunofluorescencia. Descubrimos que estos dos componentes del complejo de metiltransferasa podían ser detectados desde el comienzo del desarrollo de la retina; la expresión de Mettl3 y Mettl14 se restringió gradualmente a la capa nuclear interna (INL) y la capa de células ganglionares (GCL); se observó que Mettl3 y Mettl14 tenían patrones de expresión similares en INL y GCL retinianos maduros. En general, nuestros datos de expresión espacio-temporal proporcionan información para futuras investigaciones sobre la función de la modificación de m6A en el desarrollo de la retina.
Subject(s)
Animals , Mice , Retina/embryology , Retina/enzymology , Methyltransferases/metabolism , Staining and Labeling , Immunohistochemistry , Real-Time Polymerase Chain Reaction , Methyltransferases/genetics , Mice, Inbred C57BLABSTRACT
Background METTL3 (methyltransferase like 3) and FTO (fat mass and obesity-associated protein) are criticalfor establishing and regulating the m6A (N6-methyladenosine) modification, but very little is known about thefunction of m6A in the immune system or its role in interactions within the host immune system.Methods Western blotting experiment was used to check the expression of the host proteins related to m6Amodification after H7N9 influenza virus infection. Immunofluorescence experiment was used to identifywhether the subcellular localization of related proteins. Moreover, we knocked down and over expressendogenous METTL3 or FTO in A549 cells, and then infected the cells with H7N9 to test whethermethyltransferases or demethylases affect H7N9 replication.Result We confirmed that the expression pattern of m6A proteins was altered during H7N9 infection. METTL3and FTO were located in the nucleus, and YTHDF3 was located in the cytoplasm. Furthermore, our resultsdemonstrate that downregulation of METTL3 or FTO expression in A549 cells severely impairs viral proteinexpression and H7N9 infection.Conclusions METTL3 and FTO are critical for H7N9 replication which may represent a new mechanism for thecontrol of H7N9 replication and host-pathogen interactions.
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N-methyladenosine (mA), a ubiquitous RNA modification, is installed by METTL3-METTL14 complex. The structure of the heterodimeric complex between the methyltransferase domains (MTDs) of METTL3 and METTL14 has been previously determined. However, the MTDs alone possess no enzymatic activity. Here we present the solution structure for the zinc finger domain (ZFD) of METTL3, the inclusion of which fulfills the methyltransferase activity of METTL3-METTL14. We show that the ZFD specifically binds to an RNA containing 5'-GGACU-3' consensus sequence, but does not to one without. The ZFD thus serves as the target recognition domain, a structural feature previously shown for DNA methyltransferases, and cooperates with the MTDs of METTL3-METTL14 for catalysis. However, the interaction between the ZFD and the specific RNA is extremely weak, with the binding affinity at several hundred micromolar under physiological conditions. The ZFD contains two CCCH-type zinc fingers connected by an anti-parallel β-sheet. Mutational analysis and NMR titrations have mapped the functional interface to a contiguous surface. As a division of labor, the RNA-binding interface comprises basic residues from zinc finger 1 and hydrophobic residues from β-sheet and zinc finger 2. Further we show that the linker between the ZFD and MTD of METTL3 is flexible but partially folded, which may permit the cooperation between the two domains during catalysis. Together, the structural characterization of METTL3 ZFD paves the way to elucidate the atomic details of the entire process of RNA mA modification.
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N-methyladenosine (mA), catalyzed by the methyltransferase complex consisting of Mettl3 and Mettl14, is the most abundant RNA modification in mRNAs and participates in diverse biological processes. However, the roles and precise mechanisms of mA modification in regulating neuronal development and adult neurogenesis remain unclear. Here, we examined the function of Mettl3, the key component of the complex, in neuronal development and adult neurogenesis of mice. We found that the depletion of Mettl3 significantly reduced mA levels in adult neural stem cells (aNSCs) and inhibited the proliferation of aNSCs. Mettl3 depletion not only inhibited neuronal development and skewed the differentiation of aNSCs more toward glial lineage, but also affected the morphological maturation of newborn neurons in the adult brain. mA immunoprecipitation combined with deep sequencing (MeRIP-seq) revealed that mA was predominantly enriched in transcripts related to neurogenesis and neuronal development. Mechanistically, mA was present on the transcripts of histone methyltransferase Ezh2, and its reduction upon Mettl3 knockdown decreased both Ezh2 protein expression and consequent H3K27me3 levels. The defects of neurogenesis and neuronal development induced by Mettl3 depletion could be rescued by Ezh2 overexpression. Collectively, our results uncover a crosstalk between RNA and histone modifications and indicate that Mettl3-mediated mA modification plays an important role in regulating neurogenesis and neuronal development through modulating Ezh2.
Subject(s)
Animals , Adenosine , Metabolism , Adult Stem Cells , Cell Biology , Metabolism , Brain , Metabolism , Cell Differentiation , Genetics , Cell Proliferation , Enhancer of Zeste Homolog 2 Protein , Metabolism , Gene Expression Regulation , Methyltransferases , Metabolism , Mice, Inbred C57BL , Neural Stem Cells , Cell Biology , Metabolism , Neurogenesis , Genetics , Neurons , Cell Biology , Metabolism , RNA, Messenger , Genetics , MetabolismABSTRACT
In post-transcriptional mRNA modification, m⁶A has been observed in a wide range of eukaryotes. METTL3, as a component of methyltransferase complex for m⁶A modification, regulates mouse naïve pluripotency and influences mRNA stability, especially affecting the expression level of the key pluripotent transcription factors. To reveal the expression pattern of the porcine METTL3 gene, we analyzed METTL3 expression level in different porcine tissues, somatic cells, and induced pluripotent stem cells (piPSCs) by RT-PCR. To identify the function of METTL3 for regulation of the expression of porcine pluripotent genes, we cloned a 1 859-bp coding sequence of METTL3 and synthesized a shRNA against METTL3. When knocking down METTL3 expression in piPSCs, the cell type of piPSCs became naïve-like morphology, alkaline phosphatase activity was increased, and expression level of pluripotent genes NANOG, OCT4 and LIN28A was significantly elevated. In addition, piPSCs cultured in medium containing 10 mmol/L cycloleucine for 48 h exhibited the similar result as that knocked down METTL3. These findings set the stage for optimization of piPS culture condition and further study on the roles of m6A in piPSCs.