FIGURE 2.

SREBP-1c suppresses the endogenous activity of PDX-1 in β cells but not in non-β cells. A, schematic diagram of the −2721 to +50-bp region of the mouse Pdx-1. Organization of distal enhancer/proximal regions shows the key elements and transactivating factors involved in regulation of PDX-1 transcription. B, PDX-1 (−2.7 k)-Luc or the empty vector pGL3-Luc and pSV-β-gal were cotransfected with indicated amounts of CMV-SREBP-1c in HIT (n = 6) and HepG2 cells (n = 6). Luciferase activity was normalized to the pSV-β-gal values. pGL3-Luc activity was set to 1.0. C, various lengths of Pdx-1 promoter luciferase constructs and pSV-β-gal were cotransfected with or without CMV-SREBP-1c (0.125 μg) in HIT cells (n = 3–8). The pGL3-Luc activity of empty vector was set to 1.0. Data are means ± S.E.