Regulation of fatty acid synthase gene transcription Sequences that confer a

We have previously reported induction of fatty acid synthase ment with 10 nM insulin increased CAT activity by 2.1 + 0.2-, (FAS) gene expression by insulin and adipocyte differentiation in 2.6+ 0.1-, 2.0 + 0.2and 1.7 + 0.2-fold respectively in 3T3-LI 3T3-L1 cells. In order to identify sequences responsible for adipocytes transiently transfected with 2100CAT, -1400CAT, insulin regulation of the FAS gene, chimaeric constructs con-1009CAT and 332CAT plasmids. CAT activity was taining serial deletions of the 5'-flanking region of the rat FAS increased by 3.0 + 0.3and 3.5 + 0.6-fold respectively by insulin gene ligated to the chloramphenicol acetyltransferase (CAT) treatment in adipocytes stably transfected with 21OOCAT and reporter gene were prepared and transfected into 3T3-L1 cells. 1009CAT plasmids. When insulin-responsive H4IIE hepatoma Plasmids containing 2100 (-2100CAT), 1400 (-1400CAT), cells were transiently transfected with -21OOCAT, 1400CAT, 1009 (-1009CAT) and 332 (332CAT) bp of FAS 5' flanking -1009CAT and -332CAT plasmids and then treated with sequences exhibited comparable basal CAT activities in 3T3-L1 10 nM insulin, CAT activity increased by 3.1-, 3.1 + 0.8-, preadipocytes. This activity was 3-fold higher when these 3.0 + 0.7and 2.3 + 0.5-fold respectively in serum-free media, and constructs were transiently transfected into 3T3-LI adipocytes. by 2.6+ 0.4-, 3.3 + 0.9-, 3.1 + 0.4and 2.9 + 0.6-fold respectively Stably transfected 3T3-Ll cells also exhibited a 3-fold increase in in the presence of 0.50% serum. These results indicate that CAT activity upon adipocyte differentiation, indicating that sequences responsible for insulin regulation of FAS gene are sequences required for the differentiation-dependent increase in also located within 332 bp of the transcription start site. FAS expression are located within the 332 bp promoter. Treat-