Control mechanisms of gene expression of an enzyme and a polypeptide hormone involved in the lipid metabolism in higher animals

TLDR: The regulation of lactose operon in Escherichia coli has been discussed as a model system for studies on the regulation of gene expression in animal systems and specific polysomes involved in the synthesis of acetyl-CoA carboxylase are identified.

Abstract: We have discussed the regulatory mechanisms of gene expression in higher animals, covering the following aspects on the basis of our recent results: 1. The regulation of lactose operon inEscherichia coli has been discussed as a model system for studies on the regulation of gene expression in animal systems. 2. Acetyl-CoA carboxylase plays a critical role in the regulation of biosynthesis of long-chain fatty acids. In an attempt to gain insight into the molecular mechanisms underlying the regulation of synthesis of hepatic acetyl-CoA carboxylase, we have been able to identify specific polysomes involved in the synthesis of this enzyme. Furthermore, it has been demonstrated that the relative content of these polysomes in the liver correlates well with the rate of hepatic synthesis of the enzyme under different dietary and hormonal conditions. 3. The pituitary hormone, corticotropin (ACTH), which is a single polypeptide consisting of 39 amino acids, has some interesting features with respect to the regulation of its biosynthesis. First of all, we have attempted to synthesize ACTH in a cell-free heterologous system. Our studies indicate that ACTH mRNA is translated in wheat germ extracts into a product which contains the amino acid sequence of ACTH but is much larger (M.W. approximately 35,000) than this hormone (M.W. approximately 4,500).