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DNA polymerase β, a member of the X-family of DNA polymerases, undergoes complex regulations both in vitro and in vivo through various posttranslational modifications, including phosphorylation and methylation. The impact of these modifications varies depending on the specific amino acid undergoing alterations. In vitro, methylation of DNA polymerase β with the enzyme protein arginine methyltransferase 6 (PRMT6) at R83 and R152 enhances polymerase activity by improving DNA binding and processivity. Although these studies have shown that methylation improves DNA binding, the underlying mechanism of enhancement of polymerase activity in terms of structure and dynamics remains poorly understood. To address this gap, we modeled the methylated enzyme/DNA complex and conducted a microsecond-long simulation in the presence of Mg ions. Our results revealed significant structural changes induced by methylating both R83 and R152 sites in the enzyme. Specifically, these changes caused the DNA fragment to move closer to the C- and N-subdomains, forming additional hydrogen bonds. Furthermore, the cross-correlation map demonstrated that methylation enhanced long-range correlations within the domains/subdomains of DNA polymerase β, along with an increase in the linear mutual information value between the domains/subdomains and DNA fragments. The graph connectivity network also illustrated that methylation modulates the information pathway and identifies residues exhibiting long-distance coupling with the methylated sites. Our results provide an atomic-level understanding of the structural transition induced by methylation, shedding light on the mechanisms underlying the methylation-induced enhancement of activity in DNA polymerase β. 

DNA polymerase β (pol β ) is a member of the X- family of DNA polymerases that catalyze the distributive addition of nucleoside triphosphates during base excision DNA repair. Previous studies showed that the enzyme was phosphorylated in vitro with PKC at two serines (44 and 55), causing loss of DNA polymerase activity but not DNA binding. In this work, we have investigated the phosphorylation-induced conformational changes in DNA polymerase β in the presence of Mg ions. We report a comprehensive atomic resolution study of wild type and phosphorylated DNA polymerase using molecular dynamics (MD) simulations. The results are examined via novel methods of internal dynamics and energetics analysis to reveal the underlying mechanism of conformational transitions observed in DNA pol β . The results show drastic conformational changes in the structure of DNA polymerase β due to S44 phosphorylation. Phosphorylation-induced conformational changes transform the enzyme from a closed to an open structure. The dynamic cross-correlation shows that phosphorylation enhances the correlated motions between the different domains. Centrality network analysis reveals that the S44 phosphorylation causes structural rearrangements and modulates the information pathway between the Lyase domain and base pair binding domain. Further analysis of our simulations reveals that a critical hydrogen bond (between S44 and E335) disruption and the formation of three additional salt bridges are potential drivers of these conformational changes. In addition, we found that two of these additional salt bridges form in the presence of Mg ions on the active sites of the enzyme. These results agree with our previous study of DNA pol β S44 phosphorylation without Mg ions which predicted the deactivation of DNA pol β . However, the phase space of structural transitions induced by S44 phosphorylation is much richer in the presence of Mg ions.