Project description:Mutations in the rifampicin (Rif)-binding site of RNA polymerase (RNAP) impart antibiotic resistance and inextricably affect transcription initiation, elongation, and termination properties as well. At each step of the transcription cycle, RNAP responds to non-essential transcription factors, signaling molecules, and substrate availability. As such, the non- essential genome and its impact on fitness cost potentially represent an untapped resource for new combination therapies. Using transposon sequencing (Tn-seq), we present a genome- wide analysis of resistance cost in a clinically common rpoB H526Y mutant. Our data show that cost-compounding genes include factors that promote high transcription elongation rate, whereas cost-mitigating genes function in cell wall synthesis and division. We demonstrate that cell wall synthesis and division defects in rpoB H526Y are a consequence of an abnormally high transcription elongation rate, which is further exacerbated by superfluous activity of the uracil salvage pathway and indifference of the mutant RNAP to alarmone ppGpp. Leveraging on this knowledge, we identified drugs that are highly potent against rpoB H526Y and other RifR alleles from the same phenotypic class. Thus, genome-wide analysis of fitness cost of antibiotic resistant mutants should expedite discovery of new combination therapies and delineate cellular pathways that underlie molecular mechanisms of cost.
2021-11-25 | PXD027810 | Pride
Project description:Comparative transposon sequencing of a bacterial cell division mutant
Project description:A whole genome screen was used to assay every gene of Escherichia coli strain BW25113 to identify genes involved in susceptibility to the monobactam (beta-lactam) antibiotic aztreonam. The methodology has been called TraDIS-Xpress, and is a version of TraDIS or Tn-seq. A transposon mutant library consisting of several hundred thousand mutants was constructed using a Tn5-derived transposon incorporating an inducible outward transcribing promoter. All the mutants were grown in LB broth cultures supplemented with aztreonam at 2 x, 1 x, 0.5 x and 0.25 x MIC with induction of the transposon promoter using 0.2 mM IPTG or 1 mM IPTG or without induction. Following growth, mutants with increased susceptibility show reduced numbers and those with reduced susceptibility show increased numbers. Each condition was performed in duplicate. The methodology enable genes to be assayed by insertional inactivation or by changes in expression. Expression changes result from altered transcription from upstream transposon insertions transcribing into the gene, or downstream insertions transcribing into the gene in the reverse direction leading to RNA interference through the generation of reverse and complementary RNA. Thus, essential genes into which transposon insertions are not tolerated may be assayed also by changes in numbers of upstream or downstream insertion mutants. Changes to high throughput sequencing protocols permit the generation of nucleotide sequence reads from the known transposon sequences into the surrounding insertion site for all the mutants in the mixture simultaneously. Matching the sequence of the reads to the genome nucleotide sequence of E. coli BW25113 then allows the precise locations of all the transposon insertion sites of all the mutants to be mapped simultaneously. The relative changes in mutants between control (without) and selective condition (with aztreonam) then indicates which genes are involved in susceptibility. The numbers of sequence reads that match is reflected by the number of mutants, and so the degree of susceptibility can also be estimated.
Project description:Dnmt2 genes are highly conserved tRNA methyltransferases with biological roles in cellular stress responses. Dnmt2 has recently been implicated in transposon silencing in Drosophila but the exact molecular mechanisms are unclear. Adult Dnmt2 mutants were heat shocked and RNA sequencing was performed on visible high-molecular weight RNAs to determine the identity of up-regulated transposons. Dnmt2 mutants accumulated almost all families of transposons after heat shock, indicating a general mis-regulation of transposon silencing in Dnmt2 mutants during the stress response.
Project description:Lipid intermediates derived from sphingolipid metabolism are crucial regulators of mitochondrial function from yeast to humans. Among these intermediates, trans-2-hexadecenal (t-2hex) within the sphingolipid degradation pathway exhibits remarkable efficiency in inducing mitochondria-mediated cell death. In yeast cell cultures, the addition of t-2-hex triggers complete disintegration of the mitochondrial network, leading to subsequent cell death. This effect is particularly pronounced in yeast cells lacking the activity of the t-2-hex degrading enzyme, Hfd1. However, the molecular mechanisms of t-2-hex induction of mitochondrial dysfunction are completely unknown. In this project, we want to exploit the unprecedented power of yeast genetics to unveil novel genetic determinants involved in t-2-hex's pro-apoptotic function. To accomplish this, we employed the SATAY method, which combines saturated transposon mutagenesis with high-throughput sequencing to functionally explore the yeast genome. In our screening approach, hfd1 mutant cells harboring a plasmid-encoded inducible MiniDs transposon were induced by galactose, resulting in extensive integration of the transposon throughout the yeast genome. Cells with the plasmid excised and the transposon genomically integrated were pooled together, creating a high-density transposon library comprising approximately 2.3E+06 independent insertion mutants. Subsequently, the pooled mutant library was subjected to treatment with the mitochondria-mediated death inducer, t-2-hexadecenal. As a control, cells were also incubated with the solvent dimethyl sulfoxide (DMSO), in which hexadecenal is dissolved. Following the treatments, cells were collected for genomic DNA extraction and digestion, using restriction enzymes with frequent four-base pair recognition sites. The resulting library fragments were circularized using T4 DNA ligase, and the transposon-genome junctions were selectively amplified through PCR with outward-facing primers specific to the transposon. Finally, the pooled and purified amplicons were subjected to massive sequencing on an Illumina MiSeq platform. The obtained sequences were then aligned to the reference genome of Saccharomyces cerevisiae, allowing for the mapping of transposon insertions and the calculation of transposon counts per gene. This project enabled the identification of genes required for the resistance and toxicity to t-2hex.
Project description:The yeast Saccharomyces cerevisiae is a highly powerful model for systems genetics. While the advent of ordered deletion libraries has considerably facilitated yeast screening, it has also narrowed the diversity of screenable variants and precluded the exploration of the non-coding genome. Here, we present a versatile, time- and work-efficient method to functionally explore the yeast genome at an unprecedented throughput and resolution, using saturated transposon mutagenesis coupled to high-throughput sequencing. SAturated Transposon Analysis in Yeast (SATAY) allows the one-step mapping of all genetic loci in which a transposon can be inserted without disrupting a function necessary for cell growth. SATAY is especially suited to discover loci important for growth in various conditions. Here, we demonstrate that SATAY can be used to (2) reveal genetic interactions in single and multiple mutant strains, (1) reveal drug-resistant and -sensitive mutants, (3) detect not only essential genes, but also essential functional protein domains, and (4) generate not only null alleles, but also other informative genetic variants. Thus SATAY allows to easily explore the yeast genome at an unprecedented resolution and throughput.
Project description:Effect of ppGpp on transcript level after RelA overexpression (90 min). The cells are constructed in our lab. They are knock-out mutants in the production of ppGpp(guanosine tetraphosphate) of Legionella, complemented with an over-expression vector containing the relA gene to express the RelA protein (responsible for the ppGpp production). The aim is to follow the gene response in Legionella pneumophila after induction of ppGpp at different time points.
Project description:Effect of ppGpp on transcript level after RelA overexpression (45 min). The cells are constructed in our lab. They are knock-out mutants in the production of ppGpp(guanosine tetraphosphate) of Legionella, complemented with an over-expression vector containing the relA gene to express the RelA protein (responsible for the ppGpp production). The aim is to follow the gene response in Legionella pneumophila after induction of ppGpp at different time points.
Project description:Centromeres are chromosomal regions that serve as platforms for kinetochore assembly and spindle attachments, ensuring accurate chromosome segregation during cell division. Despite functional conservation, centromeric sequences are diverse and usually repetitive across species, making them challenging to assemble and identify. Here, we describe centromeres in the model oomycete Phytophthora sojae by combining long-read sequencing-based genome assembly and chromatin immunoprecipitation for the centromeric histone CENP-A followed by high-throughput sequencing (ChIP-seq). P. sojae centromeres cluster at a single focus in the nucleus at different life stages and during nuclear division. We report a highly contiguous genome assembly of the P. sojae reference strain, which enabled identification of 15 highly enriched CENP-A binding regions as putative centromeres. By focusing on 10 intact regions, we demonstrate that centromeres in P. sojae are regional, spanning 211 to 356 kb. Most of these regions are transposon-rich, poorly transcribed, and lack the euchromatin mark H3K4me2 but are embedded within regions with the heterochromatin marks H3K9me3 and H3K27me3.
Project description:Cytosine methylation is an important mechanism for dynamical regulation of gene expression and transposon mobility during plant developmental processes. Recently, the variation of DNA methylation has been described between wild type and DNA methylation-related mutants in Arabidopsis thaliana. However, the elaborate representation of soybean DNA methylomes remains lacking. Here, we described the epigenome maps of soybean root, stem, leaf, and cotyledon of developing seed at a single-base resolution. We confirmed the transcription start sites of genes using high-throughput sequencing and reported the DNA methylation patterns in gene and transposon regions. The correlation between gene expression and DNA methylation was revealed through transcriptome sequencing. We found CHH methylation may function in promotion of gene expression and ten cotyledon-preferred genes were identified CHH hypermethylated in cotyledon. Small RNA library sequencing showed that DNA methylation was enhanced by small RNAs not by strand-specific way, and the variation of DNA methylation between the organs was highly related with expression of small RNAs. methylomes of roots, stems, leaves, and cotyledons of developing seeds