Fatty acid synthase promoter: characterization, and transcriptional regulation by sterol regulatory element binding protein-1 in goat mammary epithelial cells.

Fatty acid synthase (FASN) is the central enzyme of the de novo fatty acid biosynthesis pathway. Although the FASN transcriptional regulatory mechanism has been elucidated clearly in many tumor cells, its mechanism is still not clear in the ruminant mammary gland. In this study, we cloned and sequenced a 1.8-kb fragment of the FASN 5' flanking region from goat genomic DNA. Multiple alignment analysis demonstrated that the entire 1.8-kb fragment has little homology but that the sub-section nearest the transcriptional start site (-203 to +1) is more conserved across species, in particular the binding motifs for transcriptional regulation. Deletion analysis revealed a putative core promoter region located in -297/-14 bp upstream of the transcription site within the high homology domain. Mutations of sterol response elements (SRE1 and SRE2) and the nuclear factor Y (NF-Y) binding site appeared to significantly down-regulate the FASN promoter activity in goat mammary epithelial cells (P<0.05). Further analysis showed that both SRE sites responded to sterol regulatory element-binding protein 1 (SREBP-1). SREBP-1 overexpression and knockdown by small interference RNA influenced the abundance of endogenous FASN. These data suggested that SREBP-1 may regulate FASN expression at the transcriptional level in the lactating goat mammary gland. Hence, the current work will contribute valuable information to understanding the molecular regulatory mechanisms of FASN during lactation.