PATTERN AND REGULATION OF ACETYL-COA CARBOXYLASE GENE-EXPRESSION

Acetyl-CoA carboxylase is the rate-limiting enzyme in the biogenesis o f long chain fatty acids. There is a single copy of the gene for acety l-CoA carboxylase per haploid chromosome set. The gene contains two pr omoters whose primary transcripts are differentially spliced resulting in multiple forms of acetyl-CoA carboxylase mRNA. These mRNA species are different in the 5'-untranslated region, but contain the same codi ng region. Generation of different forms of the mRNA is tissue specifi c and controlled by physiological conditions. Two promoters contain an extensive array of cis-elements that perceive changes in the cellular environment signalling repression and induction of long chain fatty a cid synthesis. The ability of the gene to respond to various lipogenic signals and the presence of the same coding sequence in all acetyl-Co A carboxylase mRNA species suggest that the biosynthesis of fatty acid s required for multiple functions in the cells is primarily regulated at the gene level.