Related Experiment Video
Updated: Sep 20, 2026

Steady-state, Pre-steady-state, and Single-turnover Kinetic Measurement for DNA Glycosylase Activity
Published on: August 19, 2013
Human thymine DNA glycosylase (TDG) and methyl-CpG-binding protein 4 (MBD4) excise thymine glycol (Tg) from a Tg:G
Jung-Hoon Yoon1, Shigenori Iwai, Timothy R O'Connor
1Division of Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.
Abstract:
The repair enzymes thymine DNA glycosylase (TDG) and methyl-CpG-binding protein 4 (MBD4) remove thymines from T:G mismatches resulting from deamination of 5-methylcytosine. Thymine glycol, a common DNA lesion produced by oxidative stress, can arise from oxidation of thymine or from oxidative deamination of 5-methylcytosine, and is then present opposite adenine or opposite guanine, respectively. Here we have used oligonucleotides with thymine glycol incorporated into different sequence contexts and paired with adenine or guanine. We show that TDG and MBD4 can remove thymine glycol when present opposite guanine but not when paired with adenine. The efficiency of these enzymes for removal of thymine glycol is about half of that for removal of thymine in the same sequence context. The two proteins may have evolved to act specifically on DNA mismatches produced by deamination and by oxidation-coupled deamination of 5-methylcytosine. This repair pathway contributes to mutation avoidance at methylated CpG dinucleotides.
Related Concept Videos
Mismatch Repair
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
Mismatch Repair
Proofreading
Proofreading
Errors During Replication are Corrected by the DNA Polymerase Enzyme
Base Excision Repair
The first step of...
Translesion DNA Polymerases
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...

