Kinetics and thermodynamics of BI-BII interconversion altered by T:G mismatches in DNA.
| Autor: | Westwood MN; Department of Chemistry and Biochemistry, Missouri State University, Springfield, Missouri., Johnson CC; Department of Chemistry and Biochemistry, Missouri State University, Springfield, Missouri., Oyler NA; Department of Chemistry, University of Missouri-Kansas City, Kansas City, Missouri., Meints GA; Department of Chemistry and Biochemistry, Missouri State University, Springfield, Missouri. Electronic address: garymeints@missouristate.edu. |
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| Jazyk: | angličtina |
| Zdroj: | Biophysical journal [Biophys J] 2022 May 03; Vol. 121 (9), pp. 1691-1703. Date of Electronic Publication: 2022 Mar 30. |
| DOI: | 10.1016/j.bpj.2022.03.031 |
| Abstrakt: | T:G mismatches in DNA result in humans primarily from deamination of methylated CpG sites. They are repaired by redundant systems, such as thymine DNA glycosylase (TDG) and methyl-binding domain enzyme (MBD4), and maintenance of these sites has been implicated in epigenetic processes. The process by which these enzymes identify a canonical DNA base in the incorrect basepairing context remains a mystery. However, the conserved contacts of the repair enzymes with the DNA backbone suggests a role for protein-phosphate interaction in the recognition and repair processes. We have used 31 P NMR to investigate the energetics of DNA backbone BI-BII interconversion, and for this work have focused on alterations to the activation barriers to interconversion and the effect of a mismatch compared with canonical DNA. We have found that alterations to the ΔG of interconversion for T:G basepairs are remarkably similar to U:G basepairs in the form of stepwise differences in ΔG of 1-2 kcal/mol greater than equivalent steps in unmodified DNA, suggesting a universality of this result for TDG substrates. Likewise, we see perturbations to the free energy (∼1 kcal/mol) and enthalpy (2-5 kcal/mol) of activation for the BI-BII interconversion localized to the phosphates flanking the mismatch. Overall our results strongly suggest that the perturbed backbone energetics in T:G basepairs play a significant role in the recognition process of DNA repair enzymes. (Copyright © 2022 Biophysical Society. Published by Elsevier Inc. All rights reserved.) |
| Databáze: | MEDLINE |
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