Project description:Initiation of bacterial DNA replication takes place at the origin of replication (oriC), a region characterized by the presence of multiple DnaA boxes that serve as the binding sites for the master initiator protein DnaA. The absence or failure of DNA replication can result in bacterial cell growth arrest or death. Here, we aimed to uncover the physiological and molecular consequences of stopping replication in the model bacterium Bacillus subtilis. For this purpose, DNA replication was blocked using a CRISPRi approach specifically targeting DnaA boxes 6 and 7, which are essential for replication initiation. We characterized the phenotype of these cells and analyzed the overall changes in the proteome using quantitative mass spectrometry. Cells with arrested replication were elongating and not dividing but showed no evidence of DNA damage response (DDR). Moreover, these cells did not cease translation over time. This study sets the ground for future research on non-replicating but translationally active B. subtilis, which might be valuable for biotechnological applications.
Project description:DNA gyrase is an essential enzyme whose activity is required for DNA replication and chromosome maintenance. Inhibition of gyrase results in multiple physiological effects including changes in DNA superhelicity, replication arrest and DNA damage. Using genetic, genomic, statistical and biochemical techniques, we have untangled the contribution of individual effects, assessed their relative significance and concluded that: i) DNA replication is required for the formation of spatial transcriptional domains; ii) transcriptional response to gyrase inhibition is coordinated between at least two modules involved in DNA maintenance, relaxation and damage response; iii) genes whose transcriptional response to gyrase inhibition does not depend on the activity of topoisomerase I can be classified on the basis of the GC excess in their upstream and coding sequences into, respectively, activated and repressed by gyrase inhibition; iv) relaxation by topoisomerase I dominates the transcriptional response upon gyrase inhibition, followed by the effects of replication and RecA. Keywords: time course
Project description:Lentiviral accessory genes enhance replication through diverse mechanisms. HIV-1 accessory protein Vpr modulates the host DNA damage response (DDR) at multiple steps through DNA damage, cell cycle arrest, the degradation of host proteins, and both the activation and repression of DDR signaling. Vpr also alters host and viral transcription; however, the connection between Vpr-mediated DDR modulation and transcriptional activation remains unclear. Here, we determined the cellular consequences of Vpr-induced DNA damage using Vpr mutants that allow us to separate the ability of Vpr to induce DNA damage from cell cycle arrest and other DDR phenotypes including host protein degradation and repression of DDR. RNA-sequencing of cells expressing Vpr or Vpr mutants identified that Vpr alters cellular transcription through mechanisms both dependent and independent of cell cycle arrest. In tissue-cultured U2OS cells and primary human monocyte-derived macrophages (MDMs), Vpr-induced DNA damage activates the ATM-NEMO pathway and alters cellular transcription via NF-κB/RelA signaling. HIV-1 infection of primary MDMs validated Vpr-dependent NF-κB transcriptional activation during infection. Both virion delivered and de novo expressed Vpr induced DNA damage and activated ATM-NEMO dependent NF-κB transcription, suggesting that engagement of the DDR and transcriptional reprogramming can occur during early and late stages of viral replication. Together, our data identifies a mechanism by which Vpr activates NF-κB through DNA damage and the ATM-NEMO pathway, which occur independent of cell cycle arrest. We propose this is essential to overcoming restrictive environments, such as in macrophages, to enhance viral transcription and replication.
Project description:Actively dividing cells perform robust and accurate DNA replication during fluctuating nutrient availability, yet factors that prevent disruption of replication remain largely unknown. Here we report that DksA, a nutrient-responsive transcription factor, ensures replication completion in Escherichia coli. In the absence of DksA, replication is rapidly arrested upon amino acid starvation. This replication arrest occurs independently of exogenous DNA damage, yet it induces the DNA damage response and recruits the main recombination protein RecA. This microarray experiment compares the transcriptional responses to amino acid starvation in wild-type and delta dksA cells. The SOS-regulated genes are highly induced in delta dksA cells.
Project description:To investigate the possible genes regulated by the DNA binding protein MraZ The bacterial division and cell wall (dcw) cluster is a highly conserved region of the genome which encodes several essential cell division factors including the central divisome protein FtsZ. Understanding the regulation of this region is key to our overall understanding of the division process. mraZ is found at the 5’ end of the dcw cluster and previous studies have described MraZ as a sequence-specific DNA binding protein. In this article, we investigate MraZ to elucidate its role in Bacillus subtilis. Through our investigation, we demonstrate that increased levels of MraZ result in lethal filamentation due to repression of its own operon (mraZ-mraW-ftsL-pbpB). We observe rescue of filamentation upon decoupling ftsL expression, but not other genes in the operon, from MraZ control. Our data suggests that regulation of the mra operon may be an alternative way for cells to quickly arrest cytokinesis potentially during entry into stationary phase and in the event of DNA replication arrest. Furthermore, through timelapse microscopy we were able to identify that overexpression of mraZ or depletion of FtsL results in de-condensation of the FtsZ ring (Z-ring). Using fluorescent D-amino acid labelling, we also observed that coordinated peptidoglycan insertion at division site is dysregulated in the absence of FtsL. Thus, we reveal the precise role of FtsL is in Z-ring maturation and focusing septal peptidoglycan synthesis.