Identification and characterization of Oct-1 binding to the vWF AT-rich NRE, to the consensus Oct-1 binding site, and to the VCAM-1 promoter octamer-like sequence. Double-stranded oligonucleotides were labeled and incubated with nuclear extracts from HeLa cells before electrophoresis as described in the Materials and Methods. (A) Sequences of the probes used for MSA. These probes spanned the vWF AT-rich NRE between nt −142 and −114 (NRE1), the binding site for the bipartite POU domain of Oct-1 (Oct), and the octamer-like silencer element in the VCAM-1 promoter (VCAM). The competitors NRE1, NRE1m (the mutated base pairs in the AT-rich element are underlined), Oct, and VCAM were used at the indicated molar excess. (B, C, and D) Mobility shift assays with probes NRE, Oct, and VCAM. Arrows show the specific retarded complex 1 and the supershifted complexes between Oct-1 and the probes (S) as described in the text. Supershifts with probe NRE were performed with two different antibodies, an anti–Oct-1/2 antibody (B, left panel) and an antibody specific to Oct-1 (B, right panel). The supershifted complex S is situated just underneath the level of the wells of the polyacrylamide gel.