N-methyladenosine mediates arsenite-induced human keratinocyte transformation by suppressing p53 activation.

N-methyladenosine (mA), the most abundant and reversible RNA modification, plays critical a role in tumorigenesis. However, whether mA can regulate p53, a leading antitumor protein remains poorly understood. In this study, we explored the regulatory role of mA on p53 activation using an arsenite-transformed keratinocyte model, the HaCaT-T cell line. We created the cell line by exposing human keratinocyte HaCaT cells to 1 μM arsenite for 5 months. We found that the cells exhibited an increased mA level along with an aberrant expression of the methyltransferases, demethylase, and readers of mA. Moreover, the cells exhibited decreased p53 activity and reduced p53 phosphorylation, acetylation, and transactivation with a high nucleus export rate of p53. Knockdown of the mA methyltransferase, METTL3 significantly decreased mA level, restoring p53 activation and inhibiting cellular transformation phenotypes in the arsenite-transformed cells. Further, using both a bioinformatics analysis and experimental approaches, we demonstrated that mA downregulated the expression of the positive p53 regulator, PRDM2, through the YTHDF2-promoted decay of PRDM2 mRNAs. We showed that mA upregulated the expression of the negative p53 regulator, YY1 and MDM2 through YTHDF1-stimulated translation of YY1 and MDM2 mRNA. Taken together, our study revealed the novel role of mA in mediating arsenite-induced human keratinocyte transformation by suppressing p53 activation. This study further sheds light on the mechanisms of arsenic carcinogenesis via RNA epigenetics.