<p>(<b>A</b>) Transcriptional regulatory activity of the <i>Csn3</i> proximal promoter in P19 cells. Schematic representations of the <i>Csn3</i> promoter 5′-deletion constructs used for transient transfections are shown on the left. P19 cells were transfected with the indicated deletion constructs and then treated with ATRA for 48 h followed by luciferase activity determination. Luciferase activity (right) was normalized against <i>Renilla</i> luciferase activity derived from cotransfected pGL4.74[<i>hRluc</i>/TK] reporter vector. Values represent the mean plus S.D. from three independent experiments. Student’s <i>t</i>-test was used to assess statistical significance. Asterisk indicates <i>P</i><0.01 compared with value of construct containing the region between −500 to +39. (<b>B</b>) Map of the mouse <i>Csn3</i> promoter region. The putative DR5 RARE (filled box) and exon 1 (open box) are shown. The numbers indicate the positions relative to the transcriptional start site (+1). Arrows under the sequence indicate the location and orientation of the potential half sites for RAR/RXR binding of putative DR5 RARE (−152/−136). (<b>C</b>) Identification of functional sites within the mouse <i>Csn3</i> promoter region. P19 cells were transfected with wild-type (WT), deleted (DR5d), or mutated (DR5m) RARE-<i>luc</i> vector and treated with ATRA for 48 h. Schematic representations of the constructs and nucleotide sequence used for transfection are shown on the left and bottom panel, respectively. The mutated bases are indicated in italics. Luciferase activity (right) was normalized to <i>Renilla</i> luciferase activity. Values represent the mean plus S.D. from three independent experiments. Student’s <i>t</i>-test was used to assess statistical significance. Asterisk indicates <i>P</i><0.01 compared with value of WT DR5 RARE-<i>luc</i> vector.</p
