Figure 4

Relation between SRE motif score and response of PS2 enhancer to SREBP-2. (a) Alignment of sequences from indicated species at positions orthologous to human PS2 sterol regulatory element (SRE). 'Human mutant' refers to the mutated human SRE with four point substitutions relative to the human wild-type. 'Dog mutant' refers to the consensus SRE introduced into dog PS2 by means of three point substitutions. (b) Luciferase assay analysis of reporter construct and the SRE binding protein (SREBP)-2 expression vector cotransfection into 293T cells. The LDLR PS2 element from each of the indicated species was tested in combination with the LDLR promoter. The Y-axis denotes SRE motif score (likeness to known SRE motifs; see Materials and methods). Response of the PS2 element to SREBP-2 is shown as the increase in luciferase expression level (arbitrary units) on activation by 3 ng SREBP-2 expression vector. Expression level increase for LDLR promoter alone is indicated by the dotted line. Error bars indicate standard deviation.