Fig. 4.

(−)-Xanthatin antagonizes etoposide-mediated generation of linear DNA. Topo IIα enzyme was pre-incubated in a buffer containing increasing concentrations of (−)-xanthatin (lanes 5–8; from 10 µM to 500 µM) in the presence or absence of etoposide (100 µM) for 30 min. Subsequently, linear DNA (pHOT-1) was detected as described in Section 2 (lanes 1–8). The lower panel shows an enlarged view of the upper panel to better allow visualization of linear DNA (indicated as LIN). The intensity of linear bands was quantified and expressed as fold-change (lane 4). NC, nicked open circular DNA; LIN, linear DNA; SC, supercoiled DNA.