GSE191170
METTL3 preferentially enhances non-m6A translation of epigenetic factors and promotes tumorigenesis (eCLIP-seq)
Methyltransferase-like 3 (METTL3) is the predominant catalytic enzyme which forms a stable complex with METTL14 and WTAP to promote m6A methylation in the nucleus. Recently, accumulating evidence has shown that METTL3 can express in the cytoplasm but the function of cytoplasmic METTL3 is not fully understood. Here, we demonstrated that METTL3 inhibition significantly delayed tumorigenesis in gastric cancer both in and ex vivo. Surprisingly, our data revealed that METTL3 could not only facilitate cancer progression via mRNA m6A modification, but also bind to numerous non-m6A-modified mRNAs, suggesting an unexpected role of METTL3 that was independent of m6A modification. Mechanistically, cytoplasm-anchored METTL3 interacted with poly(A) binding protein cytoplasmic 1 (PABPC1) to stabilize its association with cap-binding complex eIF4F, which preferentially promoted the translation of epigenetic factors without m6A modification. Clinical investigation using both xenograft models and patient samples showed that cytoplasmic distributed METTL3 was highly correlated with gastric cancer progression, and this finding could be expanded in prostate cancer patients. We therefore propose that cytoplasmic METTL3 enhances the translation of both m6A and non-m6A-modified epigenetic mRNAs thus serves as an oncogenic driver in cancer progression, and METTL3 subcellular distribution can assist diagnose and predict prognosis for cancer patients. Overall design: eCLIP sequencing of wild type and the cytoplasmic METTL3 in MGC-803 cell line