Structural basis of damage recognition by thymine DNA glycosylase: Key roles for N-terminal residues.Coey, C.T., Malik, S.S., Pidugu, L.S., Varney, K.M., Pozharski, E., Drohat, A.C.
(2016) Nucleic Acids Res 44: 10248-10258
- PubMed: 27580719
- DOI: 10.1093/nar/gkw768
- Structures With Same Primary Citation
- PubMed Abstract:
Thymine DNA Glycosylase (TDG) is a base excision repair enzyme functioning in DNA repair and epigenetic regulation. TDG removes thymine from mutagenic G·T mispairs arising from deamination of 5-methylcytosine (mC), and it processes other deamination- ...
Thymine DNA Glycosylase (TDG) is a base excision repair enzyme functioning in DNA repair and epigenetic regulation. TDG removes thymine from mutagenic G·T mispairs arising from deamination of 5-methylcytosine (mC), and it processes other deamination-derived lesions including uracil (U). Essential for DNA demethylation, TDG excises 5-formylcytosine and 5-carboxylcytosine, derivatives of mC generated by Tet (ten-eleven translocation) enzymes. Here, we report structural and functional studies of TDG 82-308 , a new construct containing 29 more N-terminal residues than TDG 111-308 , the construct used for previous structures of DNA-bound TDG. Crystal structures and NMR experiments demonstrate that most of these N-terminal residues are disordered, for substrate- or product-bound TDG 82-308 Nevertheless, G·T substrate affinity and glycosylase activity of TDG 82-308 greatly exceeds that of TDG 111-308 and is equivalent to full-length TDG. We report the first high-resolution structures of TDG in an enzyme-substrate complex, for G·U bound to TDG 82-308 (1.54 Å) and TDG 111-308 (1.71 Å), revealing new enzyme-substrate contacts, direct and water-mediated. We also report a structure of the TDG 82-308 product complex (1.70 Å). TDG 82-308 forms unique enzyme-DNA interactions, supporting its value for structure-function studies. The results advance understanding of how TDG recognizes and removes modified bases from DNA, particularly those resulting from deamination.
University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA.