Effect of multimerization-defective mutants of full-length INI1 on in vitro integration. A, 15–35% glycerol gradient centrifugation of wild type INI1 and DD mutants. Fractions were analyzed by Western blot using anti-His antibody as probe. B, GST pulldown experiment with GST or GST-fused INI1 and HAP eluate of wild type and mutant His-INI1 as shown. Bound proteins were analyzed by Western blot using anti-His antibody as probe. The same blots were stripped and probed with anti-GST antibodies. C, GST pulldown of wild type INI1 and DD mutants and E3 with glutathione-Sepharose 4B beads coupled to GST or GST-IN at different salt concentrations. Bound proteins were analyzed by Western blot using anti-His antibody as probe. The same blots were stripped and probed with anti-IN (integrase) antibodies. D, in vitro integration (stimulation) assay with wild type (WT), DD mutants, and E3 INI1 HAP eluate at 100 mm salt. STP, strand transfer product. E, in vitro integration (inhibition) assay with wild type, DD mutants and E3 INI1 HAP eluate at 100 mm salt.