Different effects of ppGpp on Escherichia coli DNA replication in vivo and in vitro☆

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Abstract

Inhibition of Escherichia coli DNA replication by guanosine tetraphosphate (ppGpp) is demonstrated in vitro. This finding is compatible with impairment of the DnaG primase activity by this nucleotide. However, in agreement to previous reports, we were not able to detect a rapid inhibition of DNA synthesis in E. coli cells under the stringent control conditions, when intracellular ppGpp levels increase dramatically. We suggest that the process of ppGpp-mediated inhibition of DnaG activity may be masked in E. coli cells, which could provide a rationale for explanation of differences between ppGpp effects on DNA replication in E. coli and Bacillus subtilis.

Highlights

▸ ppGpp, but not DksA, inhibits Escherichia coli DNA replication in vitro. ▸ ppGpp, but not DksA, inhibits E. coli DnaG primase activity in vitro. ▸ Elongation of E. coli DNA replication is not halted during the stringent response. ▸ Effects of ppGpp on DnaG primase activity may be masked in E. coli cells.

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(p)ppGpp: still magical?

Katarzyna Potrykus, Michael Cashel (2008)

The fundamental details of how nutritional stress leads to elevating (p)ppGpp are questionable. By common usage, the meaning of the stringent response has evolved from the specific response to (p)ppGpp provoked by amino acid starvation to all responses caused by elevating (p)ppGpp by any means. Different responses have similar as well as dissimilar positive and negative effects on gene expression and metabolism. The different ways that different bacteria seem to exploit their capacities to form and respond to (p)ppGpp are already impressive despite an early stage of discovery. Apparently, (p)ppGpp can contribute to regulation of many aspects of microbial cell biology that are sensitive to changing nutrient availability: growth, adaptation, secondary metabolism, survival, persistence, cell division, motility, biofilms, development, competence, and virulence. Many basic questions still exist. This review tries to focus on some issues that linger even for the most widely characterized bacterial strains.

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Residual guanosine 3',5'-bispyrophosphate synthetic activity of relA null mutants can be eliminated by spoT null mutations.

G GLASER, M Cashel, K Ikehara … (1991)

It was known previously that 1) the relA gene of Escherichia coli encodes an enzyme capable of guanosine 3',5'-bispyrophosphate (ppGpp) synthesis, 2) an uncharacterized source of ppGpp synthesis exists in relA null strains, and 3) cellular degradation of ppGpp is mainly due to a manganese-dependent ppGpp 3'-pyrophosphohydrolase encoded by the spoT gene. Here, the effects of spoT gene insertions and deletions are compared with analogous alterations in neighboring genes in the spo operon and found to be lethal in relA+ strains as well as slower growing in relAl backgrounds than delta relA hosts. Cells with null alleles in both the relA and spoT genes are found no longer to accumulate ppGpp after glucose exhaustion or after chelation of manganese ions by picolinic acid addition; the inability to form ppGpp is reversed by a minimal spoT gene on a multicopy plasmid. Strains apparently lacking ppGpp show a complex phenotype including auxotrophy for several amino acids and morphological alterations. We propose that the SpoT protein can either catalyze or control the alternative pathway of ppGpp synthesis in addition to its known role as a (p)ppGpp 3'-pyrophosphohydrolase. We favor the possibility that the SpoT protein is a bifunctional enzyme capable of catalyzing either ppGpp synthesis or degradation.

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rRNA transcription in Escherichia coli.

Richard L. Gourse, Wilma Ross, Tamas Gaal … (2003)

Ribosomal RNA transcription is the rate-limiting step in ribosome synthesis in bacteria and has been investigated intensely for over half a century. Multiple mechanisms ensure that rRNA synthesis rates are appropriate for the cell's particular growth condition. Recently, important advances have been made in our understanding of rRNA transcription initiation in Escherichia coli. These include (a) a model at the atomic level of the network of protein-DNA and protein-protein interactions that recruit RNA polymerase to rRNA promoters, accounting for their extraordinary strength; (b) discovery of the nonredundant roles of two small molecule effectors, ppGpp and the initiating NTP, in regulation of rRNA transcription initiation; and (c) identification of a new component of the transcription machinery, DksA, that is absolutely required for regulation of rRNA promoter activity. Together, these advances provide clues important for our molecular understanding not only of rRNA transcription, but also of transcription in general.

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Author and article information

Contributors

Grzegorz Węgrzyn

Journal

Journal ID (nlm-ta): FEBS Open Bio

Journal ID (iso-abbrev): FEBS Open Bio

Title: FEBS Open Bio

Publisher: Elsevier

ISSN (Electronic): 2211-5463

Publication date PMC-release: 6 March 2013

Publication date (Electronic): 6 March 2013

Publication date Collection: 2013

Volume: 3

Pages: 161-164

Affiliations

[0001]Department of Molecular Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland

Author notes

[* ]Corresponding author. Tel.: +48 58 523 6024; fax: +48 58 523 5501. wegrzyn@ 123456biotech.univ.gda.pl

Article

Publisher ID: FOB84

DOI: 10.1016/j.fob.2013.03.001

PMC ID: 3668537

PubMed ID: 23772389

SO-VID: 04e136d8-ea99-4e10-aaed-093c664d61f4

License:

This is an open-access article distributed under the terms of the Creative CommonsAttribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.

History

Date received : 21 January 2013

Date revision received : 26 February 2013

Date accepted : 1 March 2013

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