Fig. 6. Competition and interaction of Sox8 and Sox10 on bona fide binding sites from target gene promoters. (A) Electrophoretic mobility shift assays with the Sox10-binding sites 1-3 from the Mbp promoter (Stolt et al., 2002) as probes, and extracts from transfected N2A cells-expressing full-length Sox8 and Sox10 proteins as indicated below the lanes. Antibodies directed against Sox8 (-Sox8) or Sox10 (-Sox10) were added to some reactions during the incubation period as indicated. m, bound monomer; d, bound homodimer. Supershifted complexes are marked with an asterisk. (B) Electrophoretic mobility shift assay with site 2 from the Mbp promoter as probe and Sox8-containing N2A cell extract as protein source. Increasing amounts of a truncated Sox10 (MIC variant) (see Kuhlbrodt et al., 1998b; Schlierf et al., 2002) were added to the reactions as indicated. (C) Electrophoretic mobility shift assay with the prototypic dimeric Sox10-binding site C/C' (Peirano and Wegner, 2000) and extracts from transfected N2A cells expressing a short version of Sox8 and a long version of Sox10 either alone or in combination as indicated below the lanes. The heterodimer is indicated by an arrowhead.