Neither HTLV-I Tax nor LPS enhances binding of Oct-1 to its target octamer-binding motif. DNA binding reactions were performed with a radiolabeled Oct-1 consensus oligonucleotide. The oligonucleotide containing the octamer-binding motif was described in Materials and Methods. Nuclear extracts prepared as described in the legend to Fig 4 were used. In lanes 5 and 6, nuclear extract was incubated with anti-Oct–1 Ab at room temperature for 30 minutes. Triangle indicates increasing anti-Oct–1 Ab concentrations. In lanes 4 to 6, the total amount of added antibody in each reaction mixture was kept constant by the addition of a control antibody.