Negative regulatory element in SPAG4 promoter. Average promoter activity across two cell types, HT1080 and HCT116, of six constructs: Construct 1, SPAG4 372-bp fragment; Construct 2, SPAG4 372-bp promoter cloned in tandem duplicate to control for size; Construct 3, 500 bp of random sequence cloned upstream of the SPAG4 372-bp promoter; Construct 4, SPAG4 898-bp fragment; Construct 5, SPAG4 -898 to -372 fragment cloned upstream of heterologous promoter A; Construct 6, SPAG4 -898→372 fragment upstream of heterologous promoter B. Error bars indicate one standard deviation from the mean of four replicates of each construct.