Role of Sp1 and Sp3 in the Transcriptional Regulation of the Rat Fatty Acid Synthase Gene

Inspection of the 5′ region of the sequence of the rat fatty acid synthase (FAS) gene revealed a high GC content between −900 and +500, implying several binding sites for members of the Sp1 family of transcription factors. Using SL2 and H4IIE cells in conjunction with FAS promoter/luciferase constructs either successively deleted or containing defined deletions we characterized six GC boxes—GC-I to GC-VI—locatedbetween −557 and −83 and discovered a seventh, GC-VII, in the first intron. In vitro DNAse I- footprinting, electrophoretic mobility shift assays, and the yeast one-hybrid system indicated that Sp1 as well as Sp3 interacts with GC-I to GC-VII. Each of the GC boxes conferred Sp1-dependent transcription on the FAS-Mini promoter and in the case of GC-I, Sp1, and Sp3 exert an additive effect on FAS promoter activity.