ALKBH3‐Mediated M¹A Demethylation of METTL3 Endows Pathological Fibrosis:Interplay Between M¹A and M⁶A RNA Methylation

Epigenetic modifications serve as crucial molecular switches for pathological fibrosis; howbeit the role of m¹A in this condition remains enigmatic. Herein, it is found that ALKBH3 exerts a pro-fibrotic effect in pathological skin fibrosis by reshaping N6-methyladenosine (m⁶A) RNA modification pattern. First, ALKBH3 exhibited specific upregulation within hypertrophic scars (HTS), accompanied by N1-methyladenosine (m¹A) hypomethylation. Moreover, multiomics analyses identified METTL3, a critical writer enzyme involved in m⁶A modification, as a downstream candidate target of ALKBH3. Therapeutically, ablation of ALKBH3 inhibited the progression of HTS both in vitro and in vivo, while exogenous replenishment of METTL3 counteracted this antifibrotic effect. Mechanistically, ALKBH3 recognizes the m¹A methylation sites and prevents YTHDF2-dependent mRNA decay of METTL3 transcript. Subsequently, METTL3 stabilizes collagen type I alpha 1 chain (COL1A1) and fibronectin1 (FN1) mRNAs, two major components of extracellular matrix, and therefore eliciting the pathological transformation of HTS. This observation bridges the understanding of the link between m¹A and m⁶A methylation, the two fundamental RNA modifications, underscoring the participation of "RNA methylation crosstalk" in pathological events.