Fig. 3.

Functional analysis of the mouse5HT₃R promoter and 5′ flanking region.A, Mouse 5HT₃R promoter and upstream sequences. All conserved sites shared between the mouse and human 5HT₃R genes are shown as labeled.B, A series of deletions were created in the5HT₃R promoter and upstream regions and fused to the firefly luciferase reporter gene. The exact nucleotide location of the deletion is indicated on the side of the luciferase activity determined after transfection into either N18-TG2 or HeLa cells, as described in Materials and Methods. For each construct, triplicate samples were independently measured, and the entire experiment was performed at least four times. An additional plasmid, CMV-βGAL, was cotransfected in the transient transfections as an internal control for variation between transfection efficiencies. The p36 minimal prolactin promoter luciferase construct was used to define a basal level of transcription (Ingraham et al., 1988).