Fig. 9. Synergistic activation of the NCE by Krox20 and Sox10. Expression constructs encoding Krox20 (pKrox20) and Sox10 (pSox10) or the empty plasmid were transfected into cultured HeLa cells along with either the empty ß-globin/lacZ promoter/reporter plasmid or the wild-type NCE (Fig. 3, fragment #11) or its derivatives fused to the promoter/reporter as indicated. The putative HMG box and Krox20 binding sites are indicated with squares and circles, respectively. X, represents the mutation of these sites. A 7X multimer of a 41 nucleotide sequence spanning the putative HMG box binding sites (Fig. 5) is indicated (right). Expression plasmids were transfected at either 100 ng/plate (++) or 20 ng/plate (+). The data show the ß-galactosidase activities of one experiment performed in duplicate and is representative of two independent experiments. Values from transfections with the empty promoter/reporter and expression plasmids were arbitrarily set to one. Data from all other transfections are presented as the fold induction over this level. Error bars represent the standard error.