Effect of HIV-1 integrase on the chromatin binding activity of LEDGF/p75 ΔPWWP/AT. (a) The chromatin binding strength of LEDGF/p75 ΔPWWP/AT was determined by the salt extraction assay in LEDGF/p75-deficient HEK293T cells stably expressing LEDGF/p75 ΔPWWP/AT alone or together with Myc-tagged HIV-1 integrase. Immunoblots show the amount of LEDGF/p75 ΔPWWP/AT extracted from chromatin at different salt concentrations as detected with an anti-LEDGF Mab. (b) Chromatin binding assay. The subcellular distribution of LEDGF/p75 ΔPWWP/AT was evaluated by cellular fractionation and immunobloting with anti-LEDGF Mab in cells stably expressing this LEDGF/p75 mutant alone or together with Myc-tagged HIV-1 integrase. The S1 fraction was obtained by lysing the cells in CSK I buffer containing 150 mM NaCl. T, S1, P1, S2, and P2 are described in figure legend 2.