The Synthesis and Degradation of Lactose Operon Messenger RNA in E. coli

The control of the synthesis of the proteins of the lac operon of E. coli has formed the foundation of much of our understanding of the negative control of gene activity in procaryotic ells. The recent studies by Zubay and his collaborators (Zubay, Schwartz, and Beckwith, 1970; Zubay, this volume) and Pastan and Porlman and their coworkers (Perlman et al., this volume) have demonstrated the existence of a cyclic AMP activated protein factor which is required for the functioning of all catabolite sensitive operons in E. coli. This positive control element serves as an attractive model for the way that cells can control the function of whole sets of related genes. A thorough understanding of the underlying molecular mecha-nisms by which both the negative and positive control elements act to control ac operon function should therefore enhance our understanding of genetic control mechanisms in both procaryotic and eucaryotic ells. Indirect studies by many laboratories have demonstrated that these controls of lac operon function are mediated primarily at the tran-scriptional level (Leive and Kollin, 1967; Kaempfer