Transient growth arrest in Escherichia coli induced by chromosome condensation.

Andrea L Edwards,Valentin V Rybenkov,Kyeong S Jeong,Arkady B Khodursky,Dipen P Sangurdekar

doi:10.1371/journal.pone.0084027

Andrea L Edwards, Valentin V Rybenkov + Show 3 more

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https://doi.org/10.1371/journal.pone.0084027

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Journal: PloS one	Publication Date: Dec 23, 2013
Citations: 46	License type: CC BY 4.0

Affiliation: University of Oklahoma, University of Minnesota

Abstract

MukB is a bacterial SMC (structural maintenance of chromosome) protein that regulates the global folding of the Escherichia coli chromosome by bringing distant DNA segments together. We report that moderate overproduction of MukB may lead, depending on strain and growth conditions, to transient growth arrest. In DH5α cells, overproduction of MukB or MukBEF using pBAD expression system triggered growth arrest 2.5 h after induction. The exit from growth arrest was accompanied by the loss of the overproducing plasmid and a decline in the abundance of MukBEF. The arrested cells showed a compound gene expression profile which can be characterized by the following features: (i) a broad and deep downregulation of ribosomal proteins (up to 80-fold); (ii) downregulation of groups of genes encoding enzymes involved in nucleotide metabolism, respiration, and central metabolism; (iii) upregulation of some of the genes responsive to general stress; and (iv) degradation of the patterns of spatial correlations in the transcriptional activity of the chromosome. The transcriptional state of the MukB induced arrest is most similar to stationary cells and cells recovered from stationary phase into a nutrient deprived medium, to amino acid starved cells and to the cells shifting from glucose to acetate. The mukB++ state is dissimilar from all examined transcriptional states generated by protein overexpression with the possible exception of RpoE and RpoH overexpression. Thus, the transcription profile of MukB-arrested cells can be described as a combination of responses typical for other growth-arrested cells and those for overproducers of DNA binding proteins with a particularly deep down-regulation of ribosomal genes.

Highlights

MukBEF protein complex is a bacterial prototype of eukaryotic condensins and cohesins and plays a central role in global folding of the Escherichia coli chromosome [1,2,3,4,5]
We found that the growth arrest induced by overproduction of MukB or MukBEF is transient and occurs in a strain- and growth conditions-dependent manner
No plateau in the growth curves was detected upon overproduction of SmtA and MukEF, which do not bind DNA, some slowdown in cell growth could be observed upon overproduction of MukEF (Figure 1A). We found that both MukBEF and MukB overproducers resumed growth about nine hours after induction with a lower growth rate (Figure 1A)

Summary

Introduction

MukBEF protein complex is a bacterial prototype of eukaryotic condensins and cohesins and plays a central role in global folding of the Escherichia coli chromosome [1,2,3,4,5]. All DNA reshaping activities of the complex reside in its core SMC (structural maintenance of chromosomes) subunit MukB, whereas MukEF regulates MukBDNA interactions [3,7,10,11] and recruits MukBEF into clusters at the center of the nucleoids [11,12,13,14]. Mutational inactivation of MukBEF results in chromosome decondensation and cutting, anucleate cell formation and a severe decline in colony formation above 30uC [2,15,16]. Overproduction of MukB or MukBEF leads to chromosome condensation [16]. The overproduced MukB can rescue the chromosome decondensation phenotype of MukEF mutants but not their temperature sensitivity or anucleate cell formation [2,16]

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