Transcriptional activation of HLBS by HoxA9-VP16 expression. Transient transfection experiments were performed in HEK-293 cells using a 4X HLBS basal promoter luciferase reporter system in conjunction with Hoxa9-VP16 expression. As shown by the left side of the figure, several mutant HLBS target sequences with nucleotide substitutions (as shown by red type) were tested. Forty hours later after transfection, luciferase activity was analyzed. Luciferase activity is plotted as fold increase over. Strong activation was observed with wild type HLBS, but the HLBS-Mut2, replacing the core AATTA sequence, was inactive.