... cleaved by htopo I (Fig. 4, lanes 2 and 6).However, it is clearly visible that SF2/ASF only slightlyinhibited the cutting of DNA by either HindIII or RsaI. AtthesameconcentrationofSF2/ASFinthepresenceofhtopo ... 3, htopo I, digested with proteinaseK; 4, htopo I + SF2/ASF, no proteinase K; 5, htopo I + SF2/ASF, digested with proteinase K.Fig. 5. Inhibition of kinase activity of htopo I by DNA and campto-thecin. ... htopo I, 0.92 pmol SF2/ASF, 10 U HindIII and 15 U RsaIwere used. The mixtures were incubated for 30 min at 30 °C. Lanes: 1,HindIII; 2, HindIII + htopo I; 3, HindIII + SF2/ASF; 4, HindIII +htopo...