Molecular characterization of human acetyl-CoA synthetase, an enzyme regulated by sterol regulatory element-binding proteins

Through suppressive subtractive hybridization, we identified a new gene who se transcription is induced by sterol regulatory element-binding proteins ( SREBPs). The gene encodes acetyl-CoA synthetase (ACS), the cytosolic enzyme that activates acetate so that it can be used for lipid synthesis or for e nergy generation. ACS genes were isolated previously from yeast, but not fr om animal cells. Recombinant human ACS was produced by expressing the clone d cDNA transiently in human cells. After purification by nickel chromatogra phy, the 701-amino acid cytosolic enzyme was shown to function as a monomer . The recombinant enzyme produced acetyl-CoA from acetate in a reaction tha t required ATP. As expected for a gene controlled by SREBPs, ACS mRNA was i nduced when cultured cells were deprived of sterols and repressed by sterol addition. The pattern of regulation resembled the regulation of enzymes of fatty acid synthesis. ACS mRNA was also elevated in livers of transgenic m ice that express dominant-positive versions of all three isoforms of SREBP. We conclude that ACS mRNA, and hence the ability of cells to activate acet ate, is regulated by SREBPs in parallel with fatty acid synthesis in animal cells.