PRMT6 Inhibits Malignant Progression of Melanoma by Antagonizing Trimethylation of Histone H3K4 to Downregulate ALDH1A1 Levels

Protein arginine methyltransferase 6 (PRMT6), a member of the PRMT family capable of self-arginine methylation, is down-regulated in melanoma, but the specific mechanism is still unclear. Our work demonstrated that PRMT6 overexpression significantly inhibited the ability of melanoma cells to proliferate, tumorigenicity, migration, and invasion, whereas PRMT6 knockdown rescued these malignant behaviors of melanoma cells. Mechanistically, we identified aldehyde dehydrogenase 1A1 (ALDH1A1) as a critical downstream target of PRMT6. PRMT6 knockdown up-regulated ALDH1A1 expression, exacerbating melanoma aggressiveness in vitro. Further investigations revealed that PRMT6 modulates ALDH1A1 expression by catalyzing asymmetric dimethylation of histone H3 at arginine 2 (H3R2me2a) and antagonizing the enrichment of histone H3 lysine 4 trimethylation (H3K4me3) at the ALDH1A1 promoter. In addition, dual-luciferase experiments showed that the transcription factor KLF4 may bind to the −1800 ~ +45 sequence of PRMT6, thereby negatively regulating PRMT6 expression in melanoma. Our findings underscore the tumor-suppressive role of PRMT6 in melanoma pathogenesis, highlighting its potential as a novel therapeutic target, particularly for metastatic melanoma.