Unknown,Transcriptomics,Genomics,Proteomics

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Growth control switch by a DNA damage-inducible toxin-antitoxin system in Caulobacter

ABSTRACT: Bacterial toxin-antitoxin systems (TASs) are thought to respond to various stresses, often inducing growth-arrested (persistent) sub-populations of cells whose housekeeping functions are inhibited. However, it is not always clear whether specific targets of orthologous RNAse toxins are responsible for their phenotypic effect, which has made it difficult to accurately place the multitude of TASs within cellular and adaptive regulatory networks. Here we show that the TAS HigBA can promote and inhibit bacterial growth dependent on the dosage of HigB, a toxin regulated by the DNA damage (SOS) repressor LexA in addition to its antitoxin HigA, and the target selectivity of HigBâs mRNA cleavage activity. HigB reduced the expression of an efflux pump that is toxic to a polarity control mutant, cripples the growth of cells lacking LexA and targets the cell cycle circuitry. Thus, TASs can have outcome switching activity in bacterial adaptive (stress) and systemic (cell cycle) networks. DNA binding of the antitoxin HigA and the SOS regulator LexA was analysed by chromatin immunoprecipitation-deep sequencing, and found to overlap at only one locus, the HigBA TA system promoter

ORGANISM(S): Caulobacter crescentus NA1000

SUBMITTER: Antonio Frandi

PROVIDER: E-GEOD-76721 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The SOS response is a conserved pathway that is activated under certain stress conditions and is regulated by the repressor LexA and the activator RecA. The food-borne pathogen Listeria monocytogenes contains RecA and LexA homologs, but their roles in Listeria have not been established. In this study, we identified the SOS regulon in L. monocytogenes by comparing the transcription profiles of the wild-type strain and the ÎrecA mutant strain after exposure to the DNA damaging agent mitomycinC (MMC). The SOS response is an inducible pathway involved in DNA repair, restart of stalled replication forks, and in induction of genetic variation in stressed and stationary phase cells. It is regulated by LexA and RecA. LexA is an autoregulatory repressor which binds to a consensus sequence in the promoter region of the SOS response genes, thereby repressing transcription. A consensus LexA binding motif for L. monocytogenes has not been identified thus far. Generally, the SOS response is induced under circumstances in which single stranded DNA accumulates in the cell. This results in activation of RecA, which in turn stimulates cleavage of LexA, and ultimately in the induction of the SOS response. Keywords: stress response, loop design, SOS response, mitomycin c, listeria monocytogenes, RecA, LexA Triple loop design of 3 independent experiments (series A, B, and C) using Wt strain and recA mutant (activator of the SOS response). Sampling was done before (t=0) and 1 hour after (t=60) exposure to mitomycin C (MMC) for both the wild-type strain and the recA mutant strain. One series therefore contains 4 samples and the complete experiments consists of 12 samples. Each of the 3 series was designed in a loop (wt, t=0 =>wt, t=60 => recA, t=60 => recA, t=0 => wt, t=0). These 3 loops were connected using series B as the central loop. Series B was connected to series A as follows: wt, t=0 (B) => recA, t=0 (A) and wt, t=60 (B) => recA, t=60 (A). Series B was connected to series C as follows: recA, t=0 (B) => wt, t=0 (C) and recA, t=60 (B) => wt, t=60 (C).

Project description:Identification and characterization of HP1BP3 (a human histone H1 homologue) as a novel chromatin retention factor essential for the co-transcriptional processing of pri-miRNA. We generated BAC transgenic cells at 80% confluency (~1x107) were cross-linked with 1% formaldehyde for 10 minutes at 37Â°C, and quenched with 125 mM glycine at room temperature for 5 minutes. The fixed cells were washed twice with cold PBS, scraped, and transferred into 1 ml PBS containing protease inhibitors (Roche). After centrifugation at 700 g for 4 minutes at 4Â°C, the cell pellets were resuspended in 100 Î¼l ChIP lysis buffer (1% SDS, 10 mM EDTA, 50 mM Tris-HCl [pH 8.1] with protease inhibitors) and sonicated at 4Â°C with a Bioruptor (Diagenode) (30 seconds ON and 30 seconds OFF at highest power for 15 minutes). The sheared chromatin with a fragment length of ~200 â 600 bp) was centrifuged at 20,000 g for 15 minutes at 4Â°C). 100 Î¼l of the supernatant was used for ChIP or as input. A 1:10 dilution of the solubilized chromatin in ChIP dilution buffer (0.01% SDS, 1.1% Triton X-100, 1.2 mM EDTA, 167 mM NaCl 16.7 mM Tris-HCl [pH 8.1]) was incubated at 4Â°C overnight with 6 Î¼g/ml of a goat anti-GFP (raised against His-tagged full-length eGFP and affinity-purified with GST-tagged full-length eGFP). Immunoprecipitation was carried out by incubating with 40 Î¼l pre-cleared Protein G Sepharose beads (Amersham Bioscience) for 1 hour at 4Â°C, followed by five washes for 10 minutes with 1ml of the following buffers: Buffer I: 0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM Tris-HCl [pH 8.1], 150 mM NaCl; Buffer II: 0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM Tris-HCl [pH 8.1], 500 mM NaCl; Buffer III: 0.25 M LiCl, 1% NP-40, 1% deoxycholate, 1 mM EDTA, 10 mM Tris-HCl [pH 8.1]; twice with TE buffer [pH 8.0]. Elution from the beads was performed twice with 100 Î¼l ChIP elution buffer (1% SDS, 0.1 M NaHCO3) at room temperature (RT) for 15 minutes. Protein-DNA complexes were de-crosslinked by heating at 65Â°C in 192 mM NaCl for 16 hours. DNA fragments were purified using QiaQuick PCR Purification kit (QIAGEN) and eluted into 30 Î¼l H2O according to the manufacturerâs protocol after treatment with RNase A and Proteinase K.

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Growth control switch by a DNA damage-inducible toxin-antitoxin system in Caulobacter

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