8-Oxoguanine rearranges the active site of human topoisomerase I.
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.
Diem-Thu Thieu
DT
Lesher
Yves
Y
Pommier
Lance
L
Stewart
Matthew R
MR
Redinbo
D001483:Base Sequence; D020134:Catalytic Domain / Q000187:drug effects; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000633:toxicity; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D010649:Phenylalanine / Q000737:chemistry; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity; D014443:Tyrosine / Q000737:chemistry
D011994:Recombinant Proteins; D014443:Tyrosine; D010649:Phenylalanine; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D004264:DNA Topoisomerases, Type I