AP endonuclease

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An orally administered small molecule, lucanthone inhibits topoisomerase II and AP endonuclease and has been shown to sensitize tumor cells to radiation and chemotherapy by inhibiting DNA repair.
A similar inhibition pattern was observed with the homologous Eseheriehia coil protein, exonuclease III, but no inhibition was seen with the structurally distinct AP endonuclease E.
AP endonuclease 1 (Ape1) is the major mammalian abasic endonuclease, accounting for > 95% of the total cellular AP site incision activity (Demple and Harrison 1994).
AP endonuclease reactions (unless otherwise instructed) consisted of the following: 50 mM Hepes, pH 7.
One microgram of whole-cell extract was used to measure AP endonuclease activity, 10 [micro]g for flap endonuclease activity, and 20 [micro] for gap-filling activity, in a final volume of 10 [micro]L.
coli there are two major AP endonuclease proteins, ExoIII and EndoIV (Demple and Harrison 1994).
As shown in Figure 5, only AP endonuclease activity was markedly inactivated by Cd(II), Fe(II), and Pb(II).
In support of the idea of targeted inhibition of Ape1 in vivo, we found that Cd(II), Fe(II), and Pb(II) [but not As(III), Co(II), or Ni(II)] specifically inhibited AP endonuclease activity in whole-cell extracts but did not dramatically affect other steps of repair, such as single nucleotide gap-filling, 5'-flap endonuclease, and nick ligation activities (Figure 5).
Inhibition of AP endonuclease by lucanthone leads to the accumulation of abasic sites in DNA that are converted to lethal double-strand breaks leading to sensitization of tumor cells to alkylating agents and to radiation.
Lucanthone is an orally administered small-molecule which inhibits Topoisomerase II and AP endonuclease.