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Kinetics and Thermodynamics of BI-BII Interconversion Altered by T:G Mismatches in DNA

Overview
Journal Biophys J
Publisher Cell Press
Specialty Biophysics
Date 2022 Apr 3
PMID 35367235
Authors
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Abstract

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 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.

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References
1.
Maiti A, Morgan M, Pozharski E, Drohat A . Crystal structure of human thymine DNA glycosylase bound to DNA elucidates sequence-specific mismatch recognition. Proc Natl Acad Sci U S A. 2008; 105(26):8890-5. PMC: 2449336. DOI: 10.1073/pnas.0711061105. View

2.
Xu X, Ben Imeddourene A, Zargarian L, Foloppe N, Mauffret O, Hartmann B . NMR studies of DNA support the role of pre-existing minor groove variations in nucleosome indirect readout. Biochemistry. 2014; 53(35):5601-12. DOI: 10.1021/bi500504y. View

3.
Dow B, Malik S, Drohat A . Defining the Role of Nucleotide Flipping in Enzyme Specificity Using F NMR. J Am Chem Soc. 2019; 141(12):4952-4962. PMC: 6437012. DOI: 10.1021/jacs.9b00146. View

4.
Hare D, Shapiro L, Patel D . Wobble dG X dT pairing in right-handed DNA: solution conformation of the d(C-G-T-G-A-A-T-T-C-G-C-G) duplex deduced from distance geometry analysis of nuclear Overhauser effect spectra. Biochemistry. 1986; 25(23):7445-56. DOI: 10.1021/bi00371a029. View

5.
Hartmann B, Piazzola D, Lavery R . BI-BII transitions in B-DNA. Nucleic Acids Res. 1993; 21(3):561-8. PMC: 309153. DOI: 10.1093/nar/21.3.561. View