:"You are studying the promoter of a gene encoding a protein whose expression increases after treatment with forskolin, a drug that greatly increases the concentration of cAMP in the cell. To identify the regulatory elements of this promoter, you have made a series of constructions placing increasingly shorter fragments of the promoter in front of the luciferase reporter gene. Figure 1 schematically presents the recombinant DNA with the reporter gene and the luciferase activity in cells transfected with these recombinant DNAs under control conditions and after treatment with forskolin. What can you conclude from these results? Justify your answer."