A cancer-associated METTL14 mutation induces aberrant m6A modification, affecting tumor growth

m6A modification profiles of the CHO cells with differential recombinant protein expression using MeRIP-seq/RNA-seq

Chinese hamster ovary (CHO) cells remain the primary host system for recombinant therapeutic protein production. Enhancing transgene expression efficiency while maintaining stable production persists as a key challenge in CHO cell engineering. While N6-methyladenosine (m6A) modification - the most abundant RNA methylation - regulates RNA stability and translational efficiency, its role in modulating recombinant protein expression remains underexplored. In this study, through m6A-specific methylated RNA immunoprecipitation sequencing (MeRIP-seq) of high- (ADM-H) and low- (ADM-L) recombinant adalimumab (ADM)-producing CHO cell lines, we identified 668 differentially methylated peaks. Notably, m6A methylation patterns showed positive correlation with heavy chain (HC)/light chain (LC) expression levels between ADM-H and ADM-L cell lines. Differential expression of factors, such as Igf2bp2, Gli2, and Met correlated with PI3K-Akt and Hippo signaling pathways, suggesting m6A-mediated regulatory functions of recombinant protein expression in CHO cells. Furthermore, pharmacological inhibition of Gli2 or Met in cell culture effectively enhanced ADM production while suppressing target gene expression. These findings elucidate m6A's functional role in recombinant protein production and provide actionable strategies for CHO cell line optimization.

Lactylation increases the stability of RBM15 to drives m6A modification in non-small-cell lung cancer cells

Emerging evidence supports the involvement of N6-Methyladenosine (m6A) modification in the etiology and progression of lung adenocarcinoma (LUAD), highlighting its potential as a therapeutic target. RNA-binding protein 15 (RBM15) is a well-known m6A writer protein that enhances global m6A methylation levels by associating with the METTL3-WTAP complex. Previous studies have demonstrated that RBM15 is upregulated and exerts an oncogenic role in LUAD by promoting the N6-methyladenosine-mediated mRNA stability. However, the regulatory mechanisms of RBM15 remain elusive. In this study, we observed that L-lactate upregulates RBM15 protein levels in non-small-cell lung cancer cell lines A549 and H23 in a time- and dosage-dependent manner. Furthermore, we discovered that lactate uptake mediated by Monocarboxylate transporter 1 (MCT1) is essential for RBM15 induction. Subsequent investigations revealed that L-lactate promotes lactylation of RBM15 majorly at Lys850 (K850), while histone deacetylase 3 (HDAC3) acts as the delactylase for RBM15. Importantly, lactylation of RBM15 stabilizes itself by inhibiting proteasome-mediated ubiquitin degradation. Mutation of the lactylation site K850R disrupts the association between RBM15 and METTL3, leading to a reduction in global m6A levels. Moreover, K850R significantly abrogated RBM15-mediated cell proliferation and migration in LUAD cells. Collectively, these findings unveil lactylation as a novel regulatory mechanism affecting both stability and m6A methylation activity of RBM15 in LUAD cells.

METTL14-mediated m6A modification regulates endometrial receptivity by inhibiting SLC39A14

Endometrial receptivity is a complex process that prepares the endometrium for embryo implantation. Inadequate endometrial receptivity is one cause of implantation failure. This study aimed to explore the impact of METTL14-mediated m6A modification of SLC39A14 on endometrial stromal cells (ESCs). ESCs were transfected and subjected to CCK-8 viability assay, EdU proliferation assay, and flow cytometry cell cycle and apoptosis analyses. Autophagy-related proteins LC3, p62, and Beclin-1 were detected through western blotting. RIP was used to detect the interaction between METTL14 protein and SLC39A14 mRNA. Me-RIP was used to measure the m6A level of SLC39A14. Actinomycin D was used to assess the stability of SLC39A14 mRNA. METTL14 overexpression or SLC39A14 knockdown enhanced viability, promoted proliferation and cell cycle progression, restrained apoptosis, reduced LC3II/LC3I and Beclin-1 levels, and increased p62 expression in ESCs. METTL14 bound to SLC39A14 mRNA and increased SLC39A14 m6A modification, reducing SLC39A14 mRNA stability and SLC39A14 protein expression. SLC39A14 overexpression eliminated the effect of METTL14 overexpression on ESCs. In conclusion, METTL14 promotes proliferation and inhibits apoptosis and autophagy activation in ESCs by inhibiting SLC39A14.

Cancer mutations rewire the RNA methylation specificity of METTL3-METTL14

Chemical modification of RNAs is important for posttranscriptional gene regulation. The METTL3-METTL14 complex generates most N6-methyladenosine (m6A) modifications in messenger RNAs (mRNAs), and dysregulated methyltransferase expression has been linked to cancers. Here we show that a changed sequence context for m6A can promote oncogenesis. A gain-of-function missense mutation from patients with cancer, METTL14R298P, increases malignant cell growth in culture and transgenic mice without increasing global m6A levels in mRNAs. The mutant methyltransferase preferentially modifies noncanonical sites containing a GGAU motif, in vitro and in vivo. The m6A in GGAU context is detected by the YTH family of readers similarly to the canonical sites but is demethylated less efficiently by an eraser, ALKBH5. Combining the biochemical and structural data, we provide a model for how the cognate RNA sequences are selected for methylation by METTL3-METTL14. Our work highlights that sequence-specific m6A deposition is important and that increased GGAU methylation can promote oncogenesis.

METTL14-mediated m6A modification upregulates HOXB13 expression to activate NF-κB and exacerbate cervical cancer progression

Cervical cancer (CC) is one of the common malignant tumors in women, and the incidence rate is located in the second place of female tumors. As a major RNA N6-methyladenosine (m6A) methyltransferase, methyltransferase-like 14 (METTL14) is involved in tumor progression by catalyzing methylation modifications in mRNAs. However, the molecular mechanism of METTL14-mediated m6A modification in CC remains not fully revealed. The expression of METTL14 was detected by RT-qPCR and western blot. Cell function was assayed by cell counting kit-8 (CCK-8) assay and flow cytometry analysis. Methylated RNA immunoprecipitation (MeRIP) was used to confirm the relationship between METTL14 and homeobox B13 (HOXB13). In our study, we found that the level of METTL14 was elevated in CC tissues and cells compared with their controls. The inhibition of METTL14 significantly impaired cell proliferation and the epithelial-mesenchymal transition (EMT) process, while also induced apoptosis in HeLa and C33A cells. Furthermore, our findings indicated that homeobox B13 (HOXB13) was a target of METTL14, which positively regulated the expression of HOXB13 in an m6A-dependent manner. Rescue experiments indicated that overexpression of HOXB13 effectively reversed the tumor suppression induced by METTL14 knockdown. Finally, we confirmed that METTL14-modified HOXB13 exerted an oncogenic effect through activation of the nuclear factor kappa B (NF-κB) pathway. In conclusion, our data demonstrated that the m6A modification of HOXB13, mediated by METTL14, facilitated the advancement of CC through targeting the NF-κB pathway, which may be a potential molecular target for the treatment of CC.

Decoding the epitranscriptome: a new frontier for cancer therapy and drug resistance

As the role of RNA modification in gene expression regulation and human diseases, the "epitranscriptome" has been shown to be an important player in regulating many physiological and pathological processes. Meanwhile, the phenomenon of cancer drug resistance is becoming more and more frequent, especially in the case of cancer chemotherapy resistance. In recent years, research on relationship between post-transcriptional modification and cancer including drug resistance has become a hot topic, especially the methylation of the sixth nitrogen site of RNA adenosine-m6A (N6-methyladenosine). m6A modification is the most common post-transcriptional modification of eukaryotic mRNA, accounting for 80% of RNA methylation modifications. At the same time, several other modifications of RNA, such as N1-methyladenosine (m1A), 5-methylcytosine (m5C), 3-methylcytosine (m3C), pseudouridine (Ψ) and N7-methylguanosine (m7G) have also been demonstrated to be involved in cancer and drug resistance. This review mainly discusses the research progress of RNA modifications in the field of cancer and drug resistance and targeting of m6A regulators by small molecule modulators, providing reference for future study and development of combination therapy to reverse cancer drug resistance.

METTL14-mediated m6A mRNA modification of G6PD promotes lung adenocarcinoma

METTL14 functions as an RNA methyltransferase involved in m6A modification, influencing mRNA biogenesis, decay, and translation processes. However, the specific mechanism by which METTL14 regulates glucose-6-phosphate dehydrogenase (G6PD) to promote the progression of lung adenocarcinoma (LUAD) is not well understood. Quantitative measurement and immunohistochemistry (IHC) analysis have demonstrated higher levels of m6A in LUAD tissues compared to adjacent normal tissues. Additionally, the expression of METTL14 was significantly increased in LUAD tissues. In LUAD cell lines, both METTL14 and m6A levels were elevated compared to normal human lung epithelial cells. Knockdown of METTL14 markedly reduced LUAD cell proliferation, migration, and invasion. Conversely, overexpression of METTL14, but not the mutant form, significantly enhanced these cellular processes in LUAD. In vivo studies using nude mice with subcutaneously transplanted LUAD cells demonstrated that stable METTL14 knockdown led to notably reduced tumor volume and weight, along with fewer Ki67-positive cells and lung metastatic sites. Importantly, METTL14 knockdown reduced glycolytic activity in LUAD cells. Through a combination of RNA sequencing and MeRIP-sequencing, we identified numerous altered genes and confirmed that IGF2BP2 enhances G6PD mRNA stability after METTL14-mediated m6A modification, thereby promoting tumor growth and metastasis. Moreover, LUAD patients with higher levels of G6PD had poorer overall survival (OS). In conclusion, our study indicates that METTL14 upregulates G6PD expression post-transcriptionally through an m6A-IGF2BP2-dependent mechanism, thereby stabilizing G6PD mRNA. These findings propose potential diagnostic biomarkers and effective targets for anti-metabolism therapy in LUAD.

m6A modification of CDC5L promotes lung adenocarcinoma progression through transcriptionally regulating WNT7B expression

Cell division cycle 5-like (CDC5L) protein is implicated in the development of various cancers. However, its role in the progression of lung adenocarcinoma (LUAD) remains uncertain. Our findings revealed frequent upregulation of CDC5L in LUAD, which correlated with poorer overall survival rates and advanced clinical stages. In vitro experiments demonstrated that CDC5L overexpression stimulated the proliferation, migration, and invasion of LUAD cells, whereas CDC5L knockdown exerted suppressive effects on these cellular processes. Furthermore, silencing CDC5L significantly inhibited tumor growth and metastasis in a xenograft mouse model. Mechanistically, CDC5L activates the Wnt/β-catenin signaling pathway by transcriptionally regulating WNT7B, thereby promoting LUAD progression. Besides, METTL14-mediated m6A modification contributed to CDC5L upregulation in an IGF2BP2-dependent manner. Collectively, our study uncovers a novel molecular mechanism by which the m6A-induced CDC5L functions as an oncogene in LUAD by activating the Wnt/β-catenin pathway through transcriptional regulation of WNT7B, suggesting that CDC5L may serve as a promising prognostic marker and therapeutic target for LUAD.

Challenges to mapping and defining m6A function in viral RNA

Viral RNA molecules contain multiple layers of regulatory information. This includes features beyond the primary sequence, such as RNA structures and RNA modifications, including N6-methyladenosine (m6A). Many recent studies have identified the presence and location of m6A in viral RNA and have found diverse regulatory roles for this modification during viral infection. However, to date, viral m6A mapping strategies have limitations that prevent a complete understanding of the function of m6A on individual viral RNA molecules. While m6A sites have been profiled on bulk RNA from many viruses, the resulting m6A maps of viral RNAs described to date present a composite picture of m6A across viral RNA molecules in the infected cell. Thus, for most viruses, it is unknown if unique viral m6A profiles exist throughout infection, nor if they regulate specific viral life cycle stages. Here, we describe several challenges to defining the function of m6A in viral RNA molecules and provide a framework for future studies to help in the understanding of how m6A regulates viral infection.

Intrafamily heterooligomerization as an emerging mechanism of methyltransferase regulation

Protein and nucleic acid methylation are important biochemical modifications. In addition to their well-established roles in gene regulation, they also regulate cell signaling, metabolism, and translation. Despite this high biological relevance, little is known about the general regulation of methyltransferase function. Methyltransferases are divided into superfamilies based on structural similarities and further classified into smaller families based on sequence/domain/target similarity. While members within superfamilies differ in substrate specificity, their structurally similar active sites indicate a potential for shared modes of regulation. Growing evidence from one superfamily suggests a common regulatory mode may be through heterooligomerization with other family members. Here, we describe examples of methyltransferase regulation through intrafamily heterooligomerization and discuss how this can be exploited for therapeutic use.

Role of m6A modification in regulating the PI3K/AKT signaling pathway in cancer

The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays a crucial role in the pathogenesis of cancer. The dysregulation of this pathway has been linked to the development and initiation of various types of cancer. Recently, epigenetic modifications, particularly N6-methyladenosine (m6A), have been recognized as essential contributors to mRNA-related biological processes and translation. The abnormal expression of m6A modification enzymes has been associated with oncogenesis, tumor progression, and drug resistance. Here, we review the role of m6A modification in regulating the PI3K/AKT pathway in cancer and its implications in the development of novel strategies for cancer treatment.