Conjugated eicosapentaenoic acid inhibits human topoisomerase IB with a mechanism different from camptothecin.
Conjugated eicosapentaenoic acid (cEPA) has been found to have antitumor effects which has been ascribed to their ability to inhibit DNA topoisomerases and DNA polymerases. We here show that cEPA inhibits the catalytic activity of human topoisomerase I, but unlike camptothecin it does not stabilize the cleavable complex, indicating a different mechanism of action. cEPA inhibits topoisomerase by impeding the catalytic cleavage of the DNA substrate as demonstrated using specific oligonucleotide substrates, and prevents the stabilization of the cleavable complex by camptothecin. Preincubation of the inhibitor with the enzyme is required to obtain complete inhibition. Molecular docking simulations indicate that the preferred cEPA binding site is proximal to the active site with the carboxylic group strongly interacting with the positively charged K443 and K587. Taken together the results indicate that cEPA inhibitor does not prevent DNA binding but inhibits DNA cleavage, binding in a region close to the topoisomerase active site.
Castelli
Silvia
S
Department of Biology, University of Rome Tor Vergata, Italy.
Campagna
Alessia
A
Vassallo
Oscar
O
Tesauro
Cinzia
C
Fiorani
Paola
P
Tagliatesta
Pietro
P
Oteri
Francesco
F
Falconi
Mattia
M
Majumder
Hemanta K
HK
Desideri
Alessandro
A
D002166:Camptothecin / Q000494:pharmacology*; D004247:DNA / Q000737:chemistry / Q000187:drug effects / Q000235:genetics; D026942:DNA Topoisomerases / Q000737:chemistry / Q000302:isolation & purification; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D059003:Topoisomerase Inhibitors
D004791:Enzyme Inhibitors; D009838:Oligodeoxyribonucleotides; D059003:Topoisomerase Inhibitors; D004247:DNA; D015118:Eicosapentaenoic Acid; D026942:DNA Topoisomerases; D002166:Camptothecin