YTHDF2 promotes arsenic carcinogenesis through m⁶A-dependent SMAD7 decay and PRR5 escape from decay

YTH domain family protein 2 (YTHDF2), a decay-promoting N⁶-methyladenosine (m⁶A) binding protein, determines the fate of modified mRNA, acting as a key effector downstream of m⁶A methyltransferases and demethylases. However, how the interplay between YTHDF2 and m⁶A methyltransferases/demethylases regulates arsenic carcinogenesis remains unknown. In this study, using both in vitro (human keratinocytes treated with 1 μM arsenite for 24 weeks) and in vivo (mice exposed to 10 mg/kg/day for 12 weeks) models, we report an m⁶A-dependent mechanism through which YTHDF2 promotes arsenic carcinogenesis by activating pro-cancer signaling and suppressing anti-cancer signaling. Integrative multi-omics analyses combining time-course mRNA-seq, MeRIP-seq, and computational prediction of YTHDF2 targets identified PRR5 and SMAD7 as key YTHDF2-associated transcripts implicated in arsenic carcinogenesis. Global m⁶A levels increased by 2.38-fold (24 weeks) in keratinocytes and by 3.22-fold (12 weeks) in mouse skin. Mechanistically, the m⁶A methyltransferase METTL3 enhanced YTHDF2-mediated destabilization of SMAD7 mRNA by increasing m⁶A on SMAD7 transcripts. In contrast, the m⁶A demethylase fat mass and obesity-associated protein (FTO) reduced m⁶A on PRR5, thereby weakening YTHDF2 engagement, which allows PRR5 to escape YTHDF2-mediated decay and accumulate. Site-specific SELECT-qPCR further validated dynamic m⁶A remodeling at site 1347 of PRR5 and site 2441 of SMAD7. Functionally, YTHDF2 promoted malignant phenotypes in keratinocytes and exacerbated arsenic-induced skin lesions in mice, accompanied by activation of the PRR5-mTORC2-AKT axis and enhancement SMAD2/3 signaling. This study advances our understanding of how opposing m⁶A regulatory axes shape YTHDF2 engagement and mRNA decay outputs, thereby promoting arsenic carcinogenesis by regulating oncogenic and tumor-suppressive signaling.