2-MCA inhibited topoisomerase II activity in COLO 205
cells
2-MCA’s effect on topoisomerase II activity in COLO 205
cells was explored using increasing concentration of
2-MCA (Fig. 6b, lanes 35) or 60 mM etoposide (VP-16,
a known inhibitor of topoisomerase II and used as a
positive control, lane 6) (24). Figure 6b, upper part, demonstrates that the conversion of the supercoiled plasmid
pUC 19 to the relaxed form decreased in a dose-dependent
fashion in the presence of 2-MCA or VP-16 (please
compare lanes 36 with lane 2). These results implicate
that 2-MCA inhibited the DNA relaxation activity of
topoisomerase II in the COLO 205 cell nuclear proteins.
Moreover, this effect was further investigated using
the decatenation assay. Decatenation activity involves
the release of monomers (mini circular DNA) from the
kDNA, a large network of plasmids. The COLO 205 cells’
nuclear proteins contained topoisomerase II, which converted kinetoplast DNA to monomer DNA molecules
(Fig. 6b, lower part, please compare lane 2 with lane 1).