Fig. 4.

Integration catalyzed by HIV-1 integrase onto dissociated nucleosomes in vitro. A concerted integration assay was performed using 200 nM of HIV-1 IN, 10 ng of donor DNA, 50 ng of p601 naked or p601 plasmid chromatinized either using native histone octamers (PN Oct) or H3/H4 tetramers (PN Tet) with increasing histone/DNA ratio as reported. Typical experiment is shown in (a) and quantification of the integration products is reported in (b). Results are reported as the percentage relative to activity detected on naked DNA and pre-normalized data obtained in the control experiments using naked DNA and without FACT are reported as the percentage of integrated substrate. Selectivity assays were performed under similar conditions except that a mixture of naked p5S and either p601 assembled with native octamers was used (c) or H3/H4 tetramers (d). Quantification of the integration products detected in each vector is reported as percentage of the total integration. All values are shown as the mean ± standard deviation (error bars) of at least three independent sets of experiments. The p-values were calculated by Student’s t-test and are shown as *p < 0.05 and **p < 0.005 to represent the probability of obtaining significant differences compared with untreated conditions