Molecular stripping underpins derepression of a toxin-antitoxin system.

Transcription factors control gene expression; among these, transcriptional repressors must liberate the promoter for derepression to occur. Toxin-antitoxin (TA) modules are bacterial elements that autoregulate their transcription by binding the promoter in a T:A ratio-dependent manner, known as conditional cooperativity. The molecular basis of how excess toxin triggers derepression has remained elusive, largely because monitoring the rearrangement of promoter-repressor complexes, which underpin derepression, is challenging.

Stapled Phd Peptides Inhibit Doc Toxin Induced Growth Arrest in .

Bacterial toxin inhibition is a promising approach to overcoming antibiotic failure. In, knockout of the toxin Doc has been shown to significantly reduce the formation of antibiotic-tolerant persisters. Doc is a kinase that is inhibited in nontolerant cells by its cognate antitoxin, Phd.

Dual-Activity Fluoroquinolone-Transportan 10 Conjugates Offer Alternative Leukemia Therapy during Hematopoietic Cell Transplantation.

Hematopoietic cell transplantation (HCT) is often considered a last resort leukemia treatment, fraught with limited success due to microbial infections, a leading cause of mortality in leukemia patients. To address this critical issue, we explored a novel approach by synthesizing antileukemic agents containing antibacterial substances. This innovative strategy involves conjugating fluoroquinolone antibiotics, such as ciprofloxacin (CIP) or levofloxacin (LVX), with the cell-penetrating peptide transportan 10 (TP10).

Characterization of the Key Determinants of Phd Antitoxin Mediated Doc Toxin Inactivation in .

In the search for novel antimicrobial therapeutics, toxin-antitoxin (TA) modules are promising yet underexplored targets for overcoming antibiotic failure. The bacterial toxin Doc has been associated with the persistence of in macrophages, enabling its survival upon antibiotic exposure. After developing a novel method to produce the recombinant toxin, we have used antitoxin-mimicking peptides to thoroughly investigate the mechanism by which its cognate antitoxin Phd neutralizes the activity of Doc.

A Bacterial Cell-Based Assay To Study SARS-CoV-2 Protein-Protein Interactions.

Methods for detecting and dissecting the interactions of virally encoded proteins are essential for probing basic viral biology and providing a foundation for therapeutic advances. The dearth of targeted therapeutics for the treatment of coronavirus disease 2019 (COVID-19), an ongoing global health crisis, underscores the importance of gaining a deeper understanding of the interactions of proteins encoded by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we describe the use of a convenient bacterial cell-based two-hybrid (B2H) system to analyze the SARS-CoV-2 proteome.

Auxiliary interfaces support the evolution of specific toxin-antitoxin pairing.

Toxin-antitoxin (TA) systems are a large family of genes implicated in the regulation of bacterial growth and its arrest in response to attacks. These systems encode nonsecreted toxins and antitoxins that specifically pair, even when present in several paralogous copies per genome. Salmonella enterica serovar Typhimurium contains three paralogous TacAT systems that block bacterial translation.

Effective Drug Concentration and Selectivity Depends on Fraction of Primitive Cells.

Poor efficiency of chemotherapeutics in the eradication of Cancer Stem Cells (CSCs) has been driving the search for more active and specific compounds. In this work, we show how cell density-dependent stage culture profiles can be used in drug development workflows to achieve more robust drug activity (IC and EC) results. Using flow cytometry and light microscopy, we characterized the cytological stage profiles of the HL-60-, A-549-, and HEK-293-derived sublines with a focus on their primitive cell content.

Structure of the cytoplasmic domain of SctV (SsaV) from the Salmonella SPI-2 injectisome and implications for a pH sensing mechanism.

Bacterial type III secretion systems assemble the axial structures of both injectisomes and flagella. Injectisome type III secretion systems subsequently secrete effector proteins through their hollow needle into a host, requiring co-ordination. In the Salmonella enterica serovar Typhimurium SPI-2 injectisome, this switch is triggered by sensing the neutral pH of the host cytoplasm.

SsaV Interacts with SsaL to Control the Translocon-to-Effector Switch in the SPI-2 Type Three Secretion System.

Nonflagellar type III secretion systems (nf T3SSs) form a cell surface needle-like structure and an associated translocon that deliver bacterial effector proteins into eukaryotic host cells. This involves a tightly regulated hierarchy of protein secretion. A switch involving SctP and SctU stops secretion of the needle protein.

Activity of acetyltransferase toxins involved in Salmonella persister formation during macrophage infection.

Non-typhoidal Salmonella strains are responsible for invasive infections associated with high mortality and recurrence in sub-Saharan Africa, and there is strong evidence for clonal relapse following antibiotic treatment. Persisters are non-growing bacteria that are thought to be responsible for the recalcitrance of many infections to antibiotics. Toxin-antitoxin systems are stress-responsive elements that are important for Salmonella persister formation, specifically during infection.

Cell Density-Dependent Cytological Stage Profile and Its Application for a Screen of Cytostatic Agents Active Toward Leukemic Stem Cells.

Proliferation and expansion of leukemia is driven by leukemic stem cells (LSCs). Multidrug resistance (MDR) of LSCs is one of the main reasons of failure and relapses in acute myeloid leukemia (AML) treatment. In this study, we show that maintaining HL-60 at low cell culture density or applying a 240-day treatment with anthrapyridazone (BS-121) increased the percentage of primitive cells, which include LSCs determining the overall stage profile.

Molecular basis for the DNA damage induction and anticancer activity of asymmetrically substituted anthrapyridazone PDZ-7.

Anthrapyridazones, imino analogues of anthraquinone, constitute a family of compounds with remarkable anti-cancer activity. To date, over 20 derivatives were studied, of which most displayed nanomolar cytotoxicity towards broad spectrum of cancer cells, including breast, prostate and leukemic ones. BS-154, the most potent derivative, had IC values close to 1 nM, however, it was toxic in animal studies.

The Salmonella Effector SpvD Is a Cysteine Hydrolase with a Serovar-specific Polymorphism Influencing Catalytic Activity, Suppression of Immune Responses, and Bacterial Virulence.

Many bacterial pathogens secrete virulence (effector) proteins that interfere with immune signaling in their host. SpvD is a Salmonella enterica effector protein that we previously demonstrated to negatively regulate the NF-κB signaling pathway and promote virulence of S. enterica serovar Typhimurium in mice.