Laboratory Evolution Experiments Help Identify a Predominant Site of ΔrnhA-dnaA Constitutive Stable DNA Replication Initiation
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ABSTRACT:
ORGANISM(S): Escherichia coli str. K-12 substr. MG1655
PROVIDER: GSE135706 | GEO | 2019/09/10
REPOSITORIES: GEO
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Project description:Laboratory Evolution Experiments Help Identify a Predominant Site of ΔrnhA-dnaA Constitutive Stable DNA Replication Initiation
| PRJNA559809 | ENA
Project description:The bacterium Escherichia coli can initiate replication in the absence of the replication initiator protein DnaA and/or the canonical origin of replication oriC in a ΔrnhA background. This phenomenon, which can be primed by R-loops, is called constitutive stable DNA replication (cSDR). Whether DNA replication during cSDR initiates in a stochastic manner through the length of the chromosome or at specific sites and how E. coli can find adaptations to loss of fitness caused by cSDR remain inadequately answered. We use laboratory evolution experiments of ΔrnhA-ΔdnaA strains followed by deep sequencing to show that DNA replication preferentially initiates within a broad region located ∼0.4 to 0.7 Mb clockwise of oriC. This region includes many bisulfite-sensitive sites, which have been previously defined as R-loop-forming regions, and includes a site containing sequence motifs that favor R-loop formation. Initiation from this region would result in head-on replication-transcription conflicts at rRNA loci. Inversions of these rRNA loci, which can partly resolve these conflicts, help the bacterium suppress the fitness defects of cSDR. These inversions partially restore the gene expression changes brought about by cSDR. The inversion, however, increases the possibility of conflicts at essential mRNA genes, which would utilize only a minuscule fraction of RNA polymerase molecules, most of which transcribe rRNA genes. Whether subsequent adaptive strategies would attempt to resolve these conflicts remains an open question.IMPORTANCE The bacterium E. coli can replicate its DNA even in the absence of the molecules that are required for canonical replication initiation. This often requires the formation of RNA-DNA hybrid structures and is referred to as constitutive stable DNA replication (cSDR). Where on the chromosome does cSDR initiate? We answer this question using laboratory evolution experiments and genomics and show that selection favors cSDR initiation predominantly at a region ∼0.6 Mb clockwise of oriC. Initiation from this site will result in more head-on collisions of DNA polymerase with RNA polymerase operating on rRNA loci. The bacterium adapts to this problem by inverting a region of the genome including several rRNA loci such that head-on collisions between the two polymerases are minimized. Understanding such evolutionary strategies in the context of cSDR can provide insights into the potential causes of resistance to antibiotics that target initiation of DNA replication.
| S-EPMC7045392 | biostudies-literature
Project description:To identify potential targets of co-regulation by DnaA and Rok, we compared the transcriptional profiles of dnaA null, rok null, and dnaA null rok null mutants. Because a dnaA null mutant requires an oriC- strain background, we used an oriC- oriN+ background for all strains, to allow direct comparisons.
2015-06-13 | GSE69788 | GEO
Project description:Supporting data for Hottes et al., "DnaA coordinates replication initiation and cell cycle transcription in Caulobacter crescentus" The microarray component of this work monitors mRNA expression during the cell cycle of synchronized populations of Caulobacter crescentus cells. Transcription during the normal cell cycle is compared with transcription during a cell cycle where expression of dnaA, which encodes a key DNA replication initiation factor, is delayed. Keywords: time course, cell cycle, metabolism
2005-12-08 | GSE3171 | GEO
Project description:To identify potential targets of co-regulation by DnaA and Rok, we compared the transcriptional profiles of dnaA null, rok null, and dnaA null rok null mutants. Because a dnaA null mutant requires an oriC- strain background, we used an oriC- oriN+ background for all strains, to allow direct comparisons. We compared biological triplicates for each of the following strains: dnaA null (CAL2074), rok null (CAS196), dnaA null rok null (CAS192), and dnaA+ rok+ (CAL2083; control).
2015-06-13 | E-GEOD-69788 | biostudies-arrayexpress
Project description:Comparison of transcriptions in wild_type, delta-6 (deletion of six DnaA-box clusters (DBCs)), delta-5 and delta-DBC[yydA-yycS] strains, to see effect of the DBCs on transcription of neighboring genes and DnaA-regulated genes.
2011-07-01 | E-MEXP-3069 | biostudies-arrayexpress
Project description:In all cells, initiation of chromosome replication depends on the activity of AAA+ initiator proteins that form complexes with replication origin DNA. In bacteria, the conserved, adenosine triphosphate (ATP)-regulated initiator protein, DnaA, forms a complex with the origin, oriC, that mediates DNA strand separation and recruitment of replication machinery. Complex assembly and origin activation requires DnaA-ATP, which differs from DnaA-ADP in its ability to cooperatively bind specific low affinity sites and also to oligomerize into helical filaments. The degree to which each of these activities contributes to the DnaA-ATP requirement for initiation is not known. In this study, we compared the DnaA-ATP dependence of initiation from wild-type Escherichia coli oriC and a synthetic origin (oriCallADP), whose multiple low affinity DnaA sites bind DnaA-ATP and DnaA-ADP similarly. OriCallADP was fully occupied and unwound by DnaA-ADP in vitro, and, in vivo, oriCallADP suppressed lethality of DnaA mutants defective in ATP binding and ATP-specific oligomerization. However, loss of preferential DnaA-ATP binding caused over-initiation and increased sensitivity to replicative stress. The findings indicate both DnaA-ATP and DnaA-ADP can perform most of the mechanical functions needed for origin activation, and suggest that a key reason for ATP-regulation of DnaA is to control replication initiation frequency.
| S-EPMC6158602 | biostudies-literature
Project description:Assays 1-4: Effects of DnaA activity on S. meliloti chromosome, pSymA and pSymB replicon bias. Sheared DNA extracts of IPTG-induced vs uninduced cultures of DnaA (Assays 1,2) or Hda (Assays 3,4) overexpressors were labeled with Cy3 or Cy5 and hybridized applying dye-swap replicate design. Assay 5: Hybridization of sheared DNA of logarithmic (Cy3-labeled) vs stationary phase (Cy5-labeled) culture.
2015-10-04 | E-MTAB-3924 | biostudies-arrayexpress
Project description:Escherichia coli coordinates replication and division cycles by initiating replication at a narrow range of cell sizes. By tracking replisomes in individual cells through thousands of division cycles in wild-type and mutant strains, we were able to compare the relative importance of previously described control systems. We found that accurate triggering of initiation does not require synthesis of new DnaA. The initiation size increased only marginally as DnaA was diluted by growth after dnaA expression had been turned off. This suggests that the conversion of DnaA between its active ATP- and inactive ADP-bound states is more important for initiation size control than the total free concentration of DnaA. In addition, we found that the known ATP/ADP-converters DARS and datA compensate for each other, although the removal of them makes the initiation size more sensitive to the concentration of DnaA. Only disruption of the regulatory inactivation of DnaA (RIDA) mechanism had a radical impact on replication initiation. This result was corroborated by the finding that termination of one round of replication correlates with the next initiation at intermediate growth rates, as would be the case if RIDA-mediated conversion from DnaA-ATP to DnaA-ADP abruptly stops at termination and DnaA-ATP starts accumulating.
2023-05-12 | PXD036580 | Pride
Project description:ChIP-seq was performed to map the association of SPA-tagged DnaA across the Escherichia coli MG1655 chromosome during exponential phase growth in LB. As a control to remove background, ChIP-Seq was also performed on SPA-tagged AcpS, a protein that is not known to bind DNA.
2022-10-16 | E-MTAB-12223 | biostudies-arrayexpress