PCR reaction. (D-F) Crx transactivates mr-s transcription. Reporter plasmids for the luciferase assay are shown. Blue boxes represent Crx binding sites (D). Relative activity of the luciferase is indicated when Pro1.2k was co-transfected with Crx, Otx2, Nrl, and Crx+Nrl, respectively (E). Fold activation is indicated when Pro1.2k, mut1259, mut198, mut72 and mut all were co-transfected with the Crx expression vector (Crx+) or the empty vector (Crx-) into HEK293T cells (F). Error bars represent standard error of mean. To further examine whether Crx regulates mr-s transcription directly or not, we next performed a luciferase assay using the 1.2-kb proximal promoter region of mr-s fused to a luciferase gene as a luciferase reporter (Fig. 3D, Pro1.2k) and the Crx, Otx2, Nrl expression vectors, respectively. This 1.2-kb region of the mr-s upstream sequence contains three Crx binding consensus sequences. As shown in Fig