DNA and Chromosomes
Structural and Kinetic Analysis of Miscoding Opposite the DNA Adduct 1,N6-Ethenodeoxyadenosine by Human Translesion DNA Polymerase η
1,N6-Ethenodeoxyadenosine (1,N6-ϵdA) is the major etheno lesion formed in the reaction of DNA with epoxides substituted with good leaving groups (e.g. vinyl chloride epoxide). This lesion is also formed endogenously in DNA from lipid oxidation. Recombinant human DNA polymerase η (hpol η) can replicate oligonucleotide templates containing 1,N6-ϵdA. In steady-state kinetic analysis, hpol η preferred to incorporate dATP and dGTP, compared with dTTP. Mass spectral analysis of incorporation products also showed preferred purine (A, G) incorporation and extensive −1 frameshifts, suggesting pairing of the inserted purine and slippage before further replication.Structural and Kinetic Analysis of Nucleoside Triphosphate Incorporation Opposite an Abasic Site by Human Translesion DNA Polymerase η
Background: Abasic sites are the most common lesion in DNA.Results: Kinetic and mass spectrometric assays demonstrate that human polymerase (pol) η preferentially inserts A and G opposite an abasic site.Conclusion: Crystal structures reveal H-bonding between incoming ATP and GTP and the 5′-phosphate of the abasic moiety.Significance: Abasic site bypass by pol η follows a “purine rule” for insertion, with formation of frameshifts.
