in vivo promoter analysis of lipogenic genes

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We have focused investigation of the regulation of lipogenesis on studying the promoter activity of SREBP-1c gene, a transcription factor deeply involved in the regulation of lipogenic genes in liver. However, the regulatory mechanisms of SREBP-1c promoter remain unclear, which we consider is due to the limitation of in vitro analysis. Here we established two in vivo systems to estimate the SREBP-1c promoter activity: 1. SREBP-1c promoter-driven luciferase trangenic mice and 2. equivalent mice with adenoviral promoter-reporter fusion gene transfer into liver.1. Transgenic mouse model : we generated a transgenic mouse model that carries 2.2kb promoter region fused to the luciferase reporter gene. These transgenic mice exhibited refeeding responses of the reporter in liver and adipose tissues with extents essentially identical to those of endogenous SREBP-1c mRNA.2. Adenoviral transduction model the same results were obtained from experiments using adenovirus-mediated SREBP-1c-promoter-luciferase fusion gene transduction to liver.These data demonstrate that the regulation of SREBP-1c gene expression is at the transcription level, and that the 2.2kb 5'-flanking region is sufficient for this regulation. Especially, the latter strategy provided a feasible approach to identify the promoter regions responsible for the refeeding response of SREBP-1c expression. We are planning to further investigate the molecular mechanism of lipogenic gene regulation through these in vivo analyses.