<scp>NSUN2</scp> Exacerbates Renal Fibrosis by Inducing Epithelial‐Mesenchymal Transition Through Mediating <scp>m5C</scp> Modification of <scp>BRD4</scp>

5-methylcytosine (m5C) is an abundant RNA modification that participates in various biological processes. This study aims to elucidate the molecular mechanisms by which the m5C methyltransferase NSUN2 regulates renal fibrotic progression. Sirius red staining was employed to evaluate collagen deposition. The m5C methylation levels of BRD4 mRNA were analyzed by MeRIP. The interaction between NSUN2/ALYREF and BRD4 mRNA was validated by RIP and dual-luciferase assay. ChIP was performed to assess H3K27ac enrichment at the PDPK1 promoter region. The expression of fibrosis/epithelial-mesenchymal transition (EMT)-related markers was checked by RT-qPCR, western blotting, or immunohistochemistry. NSUN2 was upregulated in fibrotic renal tissues and cells, accompanied by increased expression of fibrotic and EMT-related proteins. Functionally, NSUN2 promoted TGF-β1-induced EMT in HK-2 cells, and its knockdown alleviated renal fibrosis in UUO rats. Mechanistically, NSUN2 enhanced BRD4 mRNA stability and expression through an m5C-ALYREF-dependent manner. Furthermore, BRD4 increased H3K27ac enrichment in the PDPK1 promoter region, thereby increasing PDPK1 expression, which facilitated the phosphorylation of AKT1 and GSK-3β (ser9) and ultimately induced EMT. NSUN2 stabilizes BRD4 mRNA in an m5C-ALYREF-dependent manner, and upregulated BRD4 enhances PDPK1 expression through H3K27ac modification, thereby modulating the AKT1/GSK-3β pathway and inducing EMT, ultimately promoting renal fibrosis.