Figure 1.

Testing of the ability of DNA-targeting compounds to induce c-trapping. (A) Examples of screening of the compounds for the presence of c-trapping upon treatment of HeLa cells with either CBL0100 or Etoposide. Representative immunoblots of soluble protein extracts and chromatin pellets of HeLa cells treated for 24 hours. Results for other drugs and cells are shown on Fig. S5-7. (B) Comparison of the kinetic of c-trapping in HT1080 cells expressing C-GFP-tagged SSRP1 via live cell imaging. Photographs of typical cell nuclei similar to >90% of cells in population. All compounds were used at 2.5μM. White frames are used to indicate nuclei where c-trapping is observed. Missing time-points for some drugs did not show any difference from untreated cells. For multiple cell images see Supplementary Figures S8-S9. (C) Comparison of potency of DNA-binding compounds to induce c-trapping in HeLa cells upon short time treatment, selected based on the kinetic of c-trapping defined in B. Representative immunoblots of soluble protein fractions and chromatin pellets of HeLa cells treated for 30 min with CBL0137, CBL0100, Aclacinomycin A and Hoechst 33342, or for 60 min with Doxorubicin and Mitoxantrone. Similar data for HCT116 cells are shown in Supplementary Fig. S13. (D and E) Analyses of correlations between cytotoxicity of the compounds and their potency in inducing c-trapping for HeLa (D) and HCT116 (E) cells. Cytotoxicity is the dose causing killing of 90% of cells upon 48 treatment (IC_90%). Bars are mean of IC_90% for three replicates within experiment ±SD. C-trapping is the dose causing redistribution of 50% of FACT from soluble to pellet fractions defined by quantitation of immunoblots (EC_50%). Bars are mean of EC_50% for SSRP1 and SPT16 subunits defined separately for soluble and protein fractions ±SD. r - Pearson correlation coefficient, p-value of correlations for n=6.