Gene regulation at-a-distance in E-coli:: new insights

The number of E. coli genes/operons regulated from sites distant from the gene, though limited, steadily increases. The regulation of the ula genes, in charge of L-ascorbate utilization, as well as the negative autoregulation of the non-related lambdaCI and 186CI repressors, for efficient switching of the corresponding phages from lysogeny to lysis, are recent examples. The interaction between the two GalR dimers, separated by 114 bp, undetectable in vitro, has been genetically mapped. lac repressor-operator loops might insulate a gene and its expression from the genomic environment. The genes in charge of nitrogen assimilation sequentially react to ammonia deprivation, via an increasing intracellular NRI concentration. Other sigma54-dependent genes are activated in response to various stimuli. (C) 2004 Academie des sciences. Published by Elsevier SAS. All rights reserved.