8-Oxoguanine rearranges the active site of human topoisomerase ILesher, D.T., Pommier, Y., Stewart, L., Redinbo, M.R.
(2002) Proc Natl Acad Sci U S A 99: 12102-12107
- PubMed: 12209008
- DOI: https://doi.org/10.1073/pnas.192282699
- Primary Citation of Related Structures:
- PubMed Abstract:
7,8-Dihydro-8-oxoguanine (8-oxoG) is the most common form of oxidative DNA damage in human cells. Biochemical studies have shown that 8-oxoG decreases the DNA cleavage activity of human topoisomerase I, an enzyme vital to DNA metabolism and stability. We present the 3.1-A crystal structure of human topoisomerase I in noncovalent complex with a DNA oligonucleotide containing 8-oxoG at the +1 position in the scissile strand. We find that 8-oxoG reorganizes the active site of human topoisomerase I into an inactive conformation relative to the structures of topoisomerase I-DNA complexes elucidated previously. The catalytic Tyr-723-Phe rotates away from the DNA cleavage site and packs into the body of the molecule. A second active-site residue, Arg-590, becomes disordered and is not observed in the structure. The docked, inactive conformation of Tyr-723-Phe is reminiscent of the related tyrosine recombinase family of integrases and recombinases, suggesting a common regulatory mechanism. We propose that human topoisomerase I binds to DNA first in an inactive conformation and then rearranges its active site for catalysis. 8-OxoG appears to impact topoisomerase I by stabilizing the inactive, DNA-bound state.
Departments of Chemistry and Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.