DC432 is a cell-permeable peptide that serves as an inhibitor of N-terminal Xaa-Pro-Lys N-methyltransferase 1 (NTMT1; IC50 = 0.054 µM), capable of binding to both NTMT1 and NTMT2 with dissociation constants (Kds) of 0.3 and 1 µM, respectively. It effectively inhibits the N-terminal dimethylation of regulator of chromosome condensation 1 (RCC1) by NTMT1 at concentrations of 10 and 50 µM in cell-free assays. Furthermore, at a concentration of 100 µM, DC432 diminishes the trimethylation of the RCC1 SPKRIA motif in HCT116 cells.