Unveiling the methyl transfer mechanisms in the epigenetic machinery DNMT3A-3 L: A comprehensive study integrating assembly dynamics with catalytic reactions

In epigenetic mechanisms, DNA methyltransferase 3 alpha (DNMT3A) acts as an initiator for DNA methylation and prevents the downstream genes from expressing. Perturbations of DNMT3A functions may cause uncontrolled gene expression, resulting in pathogenic consequences such as cancers. It is, therefore, vitally important to understand the catalytic process of DNMT3A in its biological macromolecule assembly, viz., heterotetramer: (DNMT3A-3 L)^dimer. In this study, we utilized molecular dynamics (MD) simulations, Markov State Models (MSM), and quantum mechanics/molecular mechanics simulations (QM/MM) to investigate the de novo methyl transfer process. We identified the dynamics of the key residues relevant to the insertion of the target cytosine (dC) into the catalytic domain of DNMT3A, and the detailed potential energy surface of the seven-step reaction referring to methyl transfer. Our calculated potential energy barrier (22.51 kcal/mol) approximates the former experimental data (23.12 kcal/mol). The conformational change of the 5-methyl-cytosine (5mC) intermediate was found necessary in forming a four-water chain for the elimination step, which is unique to the other DNMTs. The biological assembly facilitates the creation of such a water chain, and the elimination occurs in an asynchronized mechanism in the two catalytic pockets. We anticipate the findings can enable a better understanding of the general mechanisms of the de novo methyl transfer for fulfilling the key enzymatic functions in epigenetics. And the unique elimination of DNMT3A might ignite novel methods for designing anti-cancer and tumor inhibitors of DNMTs.