METTL3 exerts synergistic effects on m6A methylation and histone modification to regulate the function of VGF in lung adenocarcinoma

Background: Multiple genetic and epigenetic regulatory mechanisms play a vital role in tumorigenesis and development. Understanding the interplay between different epigenetic modifications and its contribution to transcriptional regulation in Cancer is essential for precision medicine. Here, we aimed to investigate the interplay between N6-methyladenosine (m6A) modifications and histone modifications in lung adenocarcinoma (LUAD).

Results: Based on the data from public databases, including chromatin property data (ATAC-seq, DNase-seq), methylated RNA immunoprecipitation Sequencing (MeRIP-seq), and gene expression data (RNA-seq), a m6A-related differentially expressed gene nerve growth factor inducible (VGF) was identified between LUAD tissues and normal lung tissues. VGF was significantly highly expressed in LUAD tissues and cells, and was associated with a worse prognosis for LUAD, silencing of VGF inhibited the malignant phenotype of LUAD cells by inactivating the PI3K/Akt/mTOR pathway. Through the weighted correlation network analysis (WGCNA) and integration of TCGA-LUAD RNA-seq and m6A methyltransferase METTL3-knockdown RNA-seq data, a significant positive correlation between METTL3 and VGF was observed. By using the MeRIP-qPCR and dual-luciferase reporter assays, we demonstrated that METTL3 knockdown decreased m6A modification level of VGF coding sequences in LUAD cells, the colorimetric m6A quantification assay also showed that METTL3 knockdown significantly decreased global m6A modification level in LUAD cells. Interestingly, we found that METTL3 knockdown also reduced VGF expression by increasing H3K36me3 modification at the VGF promoter. Further research revealed that METTL3 knockdown upregulated the expression of histone methylase SETD2, the major H3K36me3 methyltransferase, by methylating the m6A site in the 3'UTR of SETD2 mRNA in LUAD cells.

Conclusions: Overall, our results reveal that the expression of VGF in LUAD cells is regulated spatio-temporally by METTL3 through both transcriptional (via histone modifications) and post-transcriptional (via m6A modifications) mechanisms. The synergistic effect of these multiple epigenetic mechanisms provides new opportunities for the diagnosis and precision treatment of tumors.

Histone modification; Lung adenocarcinoma; METTL3; VGF; m6A modification.