METTL3 protects METTL14 from STUB1-mediated degradation to maintain m⁶ A homeostasis

N⁶ -Methyladenosine (m⁶ A) is an important RNA modification catalyzed by methyltransferase-like 3 (METTL3) and METTL14. m⁶ A homeostasis mediated by the methyltransferase (MTase) complex plays key roles in various biological processes. However, the mechanism underlying METTL14 protein stability and its role in m⁶ A homeostasis remain elusive. Here, we show that METTL14 stability is regulated by the competitive interaction of METTL3 with the E3 ligase STUB1. STUB1 directly interacts with METTL14 to mediate its ubiquitination at lysine residues K148, K156, and K162 for subsequent degradation, resulting in a significant decrease in total m⁶ A levels. The amino acid regions 450-454 and 464-480 of METTL3 are essential to promote METTL14 stabilization. Changes in STUB1 expression affect METTL14 protein levels, m⁶ A modification and tumorigenesis. Collectively, our findings uncover an ubiquitination mechanism controlling METTL14 protein levels to fine-tune m⁶ A homeostasis. Finally, we present evidence that modulating STUB1 expression to degrade METTL14 could represent a promising therapeutic strategy against cancer.