Regulation and organization of the groE and dnaK operons in Eubacteria

Abstract

groEL and dnaK are the most highly conserved protein-coding genes known. Most groEL operons and several dnaK and dnaJ operons contain a highly conserved inverted repeat (IR) sequence in their regulatory region. So far, this IR has been found only as part of the groE, dnaK and dnaJ operons and genes. In most cases, the IR is part of the operon transcript, and is involved in the regulation of expression at both the DNA and mRNA levels. A detailed analysis of groE and dnaK operons indicates that the organization of the groE operons is highly conserved. They contain only the groES and groEL genes and always in the same order. In contrast, the organization of the dnaK operons has changed during evolution: genes have been added and deleted from it, and the gene order within the operon is variable.

Conserved Gene Clusters in Bacterial Genomes Provide Further Support for the Primacy of RNA

“…In E. coli, the expression levels of nusA and infB are modulated by several RNA secondary structures upstream from nusA and the NusA protein itself may be involved as well (Plumbridge et al 1984). The structure of the groE operon is known to be highly conserved phylogenetically and typically contains a characteristic inverted repeat in the regulatory region that serves at the DNA level as an operator site and when it is transcribed determines mRNA stability (Segal and Ron 1996). Although, regulation of the rRNA operons in E. coli relies in part on DNA/protein interaction (the fis protein), it is noteworthy that there is also an important antitermination system involving nusA and nusG that facilitates transcription of the RNA products.…”

Three disparately regulated genes for σ32‐like transcription factors in Bradyrhizobium japonicum

“…Consequently, a tightly controlled expression of heat-shock genes is essential. Several mechanisms which allow induction of Hsps in prokaryotes have been documented (reviewed in Yura et al, 1993;Hecker et al, 1996;Segal and Ron, 1996).…”

rpoN, mmoR and mmoG, genes involved in regulating the expression of soluble methane monooxygenase in Methylosinus trichosporium OB3b

“…The presence of a lone mmoG gene indicates that Ms. trichosporium OB3b may possess one or more groESL operons in its genome. Many groEL genes are regulated in a negative manner by a repressor, HrcA, via binding to a 9 bp conserved inverted repeat sequence or CIRCE element (controlling inverted repeat of chaperone expression): TTAGCACTC-N 9 -GAG-TGCAA (Lemos et al, 2001;Segal & Ron, 1996). Neither a CIRCE element nor putative promoter sequences is found 59 of mmoG or mmoR in Ms. trichosporium OB3b.…”