USP25 deubiquitinates cytosolic METTL3 to impede glioma proliferation via an m6A-independent pathway.

METTL3 exhibits distinct tumorigenic roles in the nucleus and cytoplasm, but whether its post-transcriptional modifications vary by subcellular localization remains unclear. Here, we identify METTL3 as a substrate of the deubiquitinase USP25, which stabilizes cytosolic METTL3 by cleaving its K48-linked polyubiquitin chains, preventing proteasomal degradation, without affecting nuclear METTL3 or global m6A abundance. The analysis of clinical glioma samples reveals a positive correlation between USP25 and METTL3 protein levels, with both significantly upregulated in high-grade glioma. Moreover, USP25 enhances EGFR expression through cytosolic METTL3, driving glioma progression. Our findings highlight that METTL3 undergoes distinct post-translational modifications based on its subcellular localization, providing new insights into the spatial regulation of METTL3 in gliomas.