Visualization of Bacterial Genes in Action

Miller, O. L.; Hamkalo, Barbara A.; Thomas, Charles A.

doi:10.1126/science.169.3943.392

Cited by 365 publications

(230 citation statements)

References 27 publications

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“…8. It was proposed, and shown recently, that transcription and translation are tightly coupled in E. coli (25,26). If the first ribosome coupled to the RNA polymerase reaches the stop codon of the galT gene, the only way for Rho to bind to the putative Rho binding site (the CG bubble region) is when the first ribosome terminates translation and is disassembled completely; this disassembly of the ribosomal complex would leave the CG bubble free of ribosomes and available for Rho binding (Fig.…”

Section: Discussionmentioning

confidence: 99%

Two-level inhibition of galK expression by Spot 42: Degradation of mRNA mK2 and enhanced transcription termination before the galK gene

Wang

Jeon

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The Escherichia coli gal operon has the structure Pgal-galE-galTgalK-galM. During early log growth, a gradient in gene expression, named type 2 polarity, is established, as follows: galE > galT > galK > galM. However, during late-log growth, type 1 polarity is established in which galK is greater than galT, as follows: galE > galK > galT > galM. We found that type 2 polarity occurs as a result of the downregulation of galK, which is caused by two different molecular mechanisms: Spot 42-mediated degradation of the galK-specific mRNA, mK2, and Spot 42-mediated Rho-dependent transcription termination at the end of galT. Because the concentration of Spot 42 drops during the transition period of the polarity type switch, these results demonstrate that type 1 polarity is the result of alleviation of Spot 42-mediated galK down-regulation. Because the Spot 42-binding site overlaps with a putative Rho-binding site, a molecular mechanism is proposed to explain how Spot 42, possibly with Hfq, enhances Rhomediated transcription termination at the end of galT.D uring the exponential growth phase of Escherichia coli cells, transcription termination at the end of each cistron of the gal operon operates with less than 100% efficiency; a certain proportion of the transcription initiated from the two promoters of the gal operon terminates at the end of each constituent gene, galE, galT, galK, and galM, of the operon (1). The termination efficiencies measured at the end of each cistron are 16%, 29%, 65%, and 71%, respectively (1). Transcription termination at the end of each cistron generates four mRNA species: mE1, mT1, mK1, and mM1 (Fig.

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Section: Discussionmentioning

confidence: 99%

Two-level inhibition of galK expression by Spot 42: Degradation of mRNA mK2 and enhanced transcription termination before the galK gene

Wang

Jeon

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Available evidence indicates that translation initiates during transcription (22) Chromosomal Distance from tetA-mcherry (kb) 0 ng/ml aTc 100 ng/ml aTc Fig. 5.…”

Section: Discussionmentioning

confidence: 99%

Membrane protein expression triggers chromosomal locus repositioning in bacteria

Libby¹,

Roggiani

Goulian

2012

Proc. Natl. Acad. Sci. U.S.A.

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It has long been hypothesized that subcellular positioning of chromosomal loci in bacteria may be influenced by gene function and expression state. Here we provide direct evidence that membrane protein expression affects the position of chromosomal loci in Escherichia coli. For two different membrane proteins, we observed a dramatic shift of their genetic loci toward the membrane upon induction. In related systems in which a cytoplasmic protein was produced, or translation was eliminated by mutating the start codon, a shift was not observed. Antibiotics that block transcription and translation similarly prevented locus repositioning toward the membrane. We also found that repositioning is relatively rapid and can be detected at positions that are a considerable distance on the chromosome from the gene encoding the membrane protein (>90 kb). Given that membrane protein-encoding genes are distributed throughout the chromosome, their expression may be an important mechanism for maintaining the bacterial chromosome in an expanded and dynamic state.bacterial nucleoid | chromosome-membrane association | transertion S tudies of several different bacteria have revealed that their chromosomes are organized structures, with genetic loci occupying relatively defined positions along the long axis of the cell (1-7). However, the potential impact of gene function and expression state on chromosome organization and on subcellular positioning of specific loci remains relatively unexplored. Such modulation of the spatial organization of the chromosome may affect numerous cellular processes, including the regulation of gene expression, gross transcriptional control, assembly of macromolecular complexes and domains, and the generation of cellular asymmetry (8)(9)(10)(11)(12)(13)(14).One long-standing hypothesis posits that genes actively expressing membrane proteins are localized to regions proximal to the membrane (8,11,15). To date, however, there is no direct evidence for membrane protein expression affecting the subcellular positions of chromosomal loci. We therefore sought to test directly whether expressing a membrane protein affects the localization of its encoding gene in Escherichia coli. We tested two loci and found that induction of membrane protein expression rapidly results in a dramatic repositioning toward the membrane. We also show that the positions of chromosomal loci as far away as 90 kb from the induced gene are affected. This shift in position is a significant perturbation on the scale of the cell and may therefore be a major determinant of chromosome conformation. ResultsWe first tested the effect of inducing the lac operon on the intracellular position of the chromosomal lac locus. The operon lacZYA encodes the membrane protein lactose permease (LacY), in addition to two cytoplasmic proteins, beta-galactosidase (LacZ) and galactoside acetyltransferase (LacA). To follow the intracellular position of lacZYA, we inserted an array of Tet repressor binding sites (tetO) in the gene cynX, which is adjacent to lacA ...

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“…The concept that the genetic information flows from DNA to RNA by means of a transcription process before it is expressed as protein (translation) stems from experiments with prokaryotic organisms [ 1, 21. In these organisms transcription and translation proceed in one spatial unity, a ternary association of DNA, RNA and ribosomes [3]. This concept has also been adopted for eukaryotic cells with the modification that a messenger RNA (mRNA) is synthesized in the nucleus and subsequently migrates to the cytoplasm where translation occurs.…”

Section: Introductionmentioning

confidence: 99%

Transport of nuclear DNA into the cytoplasm in animal cells The complexity of the transported DNA

Koch¹,

Götz²

1972

FEBS Letters

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Visualization of Bacterial Genes in Action

Cited by 365 publications

References 27 publications

Two-level inhibition of galK expression by Spot 42: Degradation of mRNA mK2 and enhanced transcription termination before the galK gene

Two-level inhibition of galK expression by Spot 42: Degradation of mRNA mK2 and enhanced transcription termination before the galK gene

Membrane protein expression triggers chromosomal locus repositioning in bacteria

Transport of nuclear DNA into the cytoplasm in animal cells The complexity of the transported DNA

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