Transition transferases prime bacterial capsule polymerization.

Capsules are long-chain carbohydrate polymers that envelop the surfaces of many bacteria, protecting them from host immune responses. Capsule biosynthesis enzymes are potential drug targets and valuable biotechnological tools for generating vaccine antigens. Despite their importance, it remains unknown how structurally variable capsule polymers of Gram-negative pathogens are linked to the conserved glycolipid anchoring these virulence factors to the bacterial membrane. Using Actinobacillus pleuropneumoniae as an example, we demonstrate that CpsA and CpsC generate a poly(glycerol-3-phosphate) linker to connect the glycolipid with capsules containing poly(galactosylglycerol-phosphate) backbones. We reconstruct the entire capsule biosynthesis pathway in A. pleuropneumoniae serotypes 3 and 7, solve the X-ray crystal structure of the capsule polymerase CpsD, identify its tetratricopeptide repeat domain as essential for elongating poly(glycerol-3-phosphate) and show that CpsA and CpsC stimulate CpsD to produce longer polymers. We identify the CpsA and CpsC product as a wall teichoic acid homolog, demonstrating similarity between the biosynthesis of Gram-positive wall teichoic acid and Gram-negative capsules.

A multi-enzyme machine polymerizes the Haemophilus influenzae type b capsule.

Bacterial capsules have critical roles in host-pathogen interactions. They provide a protective envelope against host recognition, leading to immune evasion and bacterial survival. Here we define the capsule biosynthesis pathway of Haemophilus influenzae serotype b (Hib), a Gram-negative bacterium that causes severe infections in infants and children. Reconstitution of this pathway enabled the fermentation-free production of Hib vaccine antigens starting from widely available precursors and detailed characterization of the enzymatic machinery. The X-ray crystal structure of the capsule polymerase Bcs3 reveals a multi-enzyme machine adopting a basket-like shape that creates a protected environment for the synthesis of the complex Hib polymer. This architecture is commonly exploited for surface glycan synthesis by both Gram-negative and Gram-positive pathogens. Supported by biochemical studies and comprehensive 2D nuclear magnetic resonance, our data explain how the ribofuranosyltransferase CriT, the phosphatase CrpP, the ribitol-phosphate transferase CroT and a polymer-binding domain function as a unique multi-enzyme assembly.

Pseudomonas aeruginosa post-translational responses to elevated c-di-GMP levels.

C-di-GMP signaling can directly influence bacterial behavior by affecting the functionality of c-di-GMP-binding proteins. In addition, c-di-GMP can exert a global effect on gene transcription or translation, for example, via riboswitches or by binding to transcription factors. In this study, we investigated the effects of changes in intracellular c-di-GMP levels on gene expression and protein production in the opportunistic pathogen Pseudomonas aeruginosa. We induced c-di-GMP production via an ectopically introduced diguanylate cyclase and recorded the transcriptional, translational as well as proteomic profile of the cells. We demonstrate that rising levels of c-di-GMP under growth conditions otherwise characterized by low c-di-GMP levels caused a switch to a non-motile, auto-aggregative P. aeruginosa phenotype. This phenotypic switch became apparent before any c-di-GMP-dependent role on transcription, translation, or protein abundance was observed. Our results suggest that rising global c-di-GMP pools first affects the motility phenotype of P. aeruginosa by altering protein functionality and only then global gene transcription.

Mix-and-Match System for the Enzymatic Synthesis of Enantiopure Glycerol-3-Phosphate-Containing Capsule Polymer Backbones from Actinobacillus pleuropneumoniae, Neisseria meningitidis, and Bibersteinia trehalosi.

Capsule polymers are crucial virulence factors of pathogenic bacteria and are used as antigens in glycoconjugate vaccine formulations. Some Gram-negative pathogens express poly(glycosylglycerol phosphate) capsule polymers that resemble Gram-positive wall teichoic acids and are synthesized by TagF-like capsule polymerases. So far, the biotechnological use of these enzymes for vaccine developmental studies was restricted by the unavailability of enantiopure CDP-glycerol, one of the donor substrates required for polymer assembly. Here, we use CTP:glycerol-phosphate cytidylyltransferases (GCTs) and TagF-like polymerases to synthesize the poly(glycosylglycerol phosphate) capsule polymer backbones of the porcine pathogen Actinobacillus pleuropneumoniae, serotypes 3 and 7 (App3 and App7). GCT activity was confirmed by high-performance liquid chromatography, and polymers were analyzed using comprehensive nuclear magnetic resonance studies. Solid-phase synthesis protocols were established to allow potential scale-up of polymer production. In addition, one-pot reactions exploiting glycerol-kinase allowed us to start the reaction from inexpensive, widely available substrates. Finally, this study highlights that multidomain TagF-like polymerases can be transformed by mutagenesis of active site residues into single-action transferases, which in turn can act in trans to build-up structurally new polymers. Overall, our protocols provide enantiopure, nature-identical capsule polymer backbones from App2, App3, App7, App9, and App11, Neisseria meningitidis serogroup H, and Bibersteinia trehalosi serotypes T3 and T15. IMPORTANCE Economic synthesis platforms for the production of animal vaccines could help reduce the overuse and misuse of antibiotics in animal husbandry, which contributes greatly to the increase of antibiotic resistance. Here, we describe a highly versatile, easy-to-use mix-and-match toolbox for the generation of glycerol-phosphate-containing capsule polymers that can serve as antigens in glycoconjugate vaccines against Actinobacillus pleuropneumoniae and Bibersteinia trehalosi, two pathogens causing considerable economic loss in the swine, sheep, and cattle industries. We have established scalable protocols for the exploitation of a versatile enzymatic cascade with modular architecture, starting with the preparative-scale production of enantiopure CDP-glycerol, a precursor for a multitude of bacterial surface structures. Thereby, our approach not only allows the synthesis of capsule polymers but might also be exploitable for the (chemo)enzymatic synthesis of other glycerol-phosphate-containing structures such as Gram-positive wall teichoic acids or lipoteichoic acids.

Combined Application of Pan-AKT Inhibitor MK-2206 and BCL-2 Antagonist Venetoclax in B-Cell Precursor Acute Lymphoblastic Leukemia.

Aberrant PI3K/AKT signaling is a hallmark of acute B-lymphoblastic leukemia (B-ALL) resulting in increased tumor cell proliferation and apoptosis deficiency. While previous AKT inhibitors struggled with selectivity, MK-2206 promises meticulous pan-AKT targeting with proven anti-tumor activity. We herein, characterize the effect of MK-2206 on B-ALL cell lines and primary samples and investigate potential synergistic effects with BCL-2 inhibitor venetoclax to overcome limitations in apoptosis induction. MK-2206 incubation reduced AKT phosphorylation and influenced downstream signaling activity. Interestingly, after MK-2206 mono application tumor cell proliferation and metabolic activity were diminished significantly independently of basal AKT phosphorylation. Morphological changes but no induction of apoptosis was detected in the observed cell lines. In contrast, primary samples cultivated in a protective microenvironment showed a decrease in vital cells. Combined MK-2206 and venetoclax incubation resulted in partially synergistic anti-proliferative effects independently of application sequence in SEM and RS4;11 cell lines. Venetoclax-mediated apoptosis was not intensified by addition of MK-2206. Functional assessment of BCL-2 inhibition via Bax translocation assay revealed slightly increased pro-apoptotic signaling after combined MK-2206 and venetoclax incubation. In summary, we demonstrate that the pan-AKT inhibitor MK-2206 potently blocks B-ALL cell proliferation and for the first time characterize the synergistic effect of combined MK-2206 and venetoclax treatment in B-ALL.

Stabilizing Antibody Cocktails for Mass Cytometry.

Mass cytometry is increasingly employed in larger immune profiling studies involving data acquisitions across several days and multiple sites. For gaining a maximum of information from respective data by computational analyses, several techniques have been developed to minimize noise in mass cytometric data sets, such as sample banking, standardized instrument setup, sample barcoding, and signal normalization. However, the repeated preparation of cocktails composed of isotope-tagged antibodies remained a significant source of error. We here show that premixed antibody cocktails fail to deliver expected staining patterns when stored at 4°C for 4 weeks. As a solution, we developed and tested a cryopreservation method for highly multiplexed antibody cocktails for mass cytometry including lanthanide, palladium, and platinum conjugates that yielded stable staining patterns for at least 9 months when stored at temperatures below -80°C. Using frozen aliquots of antibody cocktails is an economic and flexible approach to significantly improve data consistency in large mass cytometry studies with repetitive staining/measurement cycles spanning several days or involving multiple data acquisition sites. © 2019 International Society for Advancement of Cytometry.

Effects of Diode Laser, Gaseous Ozone, and Medical Dressings on Enterococcus faecalis Biofilms in the Root Canal Ex Vivo.

The objective was to compare the antibacterial effects of adjunctive disinfection using diode laser and gaseous ozone compared to the medical dressings calcium hydroxide (Ca(OH)2) and chlorhexidine gel (CHX-Gel) on Enterococcus faecalis biofilms in human root canals ex vivo. Root canals of 180 human extracted teeth were infected by E. faecalis and divided into 3 main groups (G): G1, control; G2, instrumentation and irrigation using 0.9% NaCl; G3, instrumentation and irrigation using 1% NaOCl. In each main group, the following treatments were applied: gaseous ozone, diode laser, and medical dressings of Ca(OH)2 or CHX-Gel for 7 days (n = 15). Reduction of colony forming units (CFUs) inside the root canal of planktons and frequencies of adherent bacteria after treatment were calculated. Bacterial reduction was significantly affected by the irrigation protocol (p < 0.0005) and the disinfection method (p < 0.0005), and a significant interaction between both factors could be observed (p < 0.0005; ANOVA). In G3 (instrumentation using 1% NaOCl), no significant effect of disinfection methods could be demonstrated on planktonic bacteria (p = 0.062; ANOVA) and frequencies of adherent bacteria (p > 0.05; chi-square test). Instrumentation and irrigation using NaOCl combined with ozone or laser application resulted in comparable bacterial reduction on E. faecalis to the application of medical dressings.

Distribution and phylogeny of Brachyspira spp. in human intestinal spirochetosis revealed by FISH and 16S rRNA-gene analysis.

During six years as German National Consultant Laboratory for Spirochetes we investigated 149 intestinal biopsies from 91 patients, which were histopathologically diagnosed with human intestinal spirochetosis (HIS), using fluorescence in situ hybridization (FISH) combined with 16S rRNA gene PCR and sequencing. Aim of this study was to complement histopathological findings with FISH and PCR for definite diagnosis and species identification of the causative pathogens. HIS is characterized by colonization of the colonic mucosa of the human distal intestinal tract by Brachyspira spp. Microbiological diagnosis of HIS is not performed, because of the fastidious nature and slow growth of Brachyspira spp. in culture. In clinical practice, diagnosis of HIS relies solely on histopathology without differentiation of the spirochetes. We used a previously described FISH probe to detect and identify Brachyspira spp. in histological gut biopsies. FISH allowed rapid visualization and identification of Brachyspira spp. in 77 patients. In most cases, the bright FISH signal already allowed rapid localization of Brachyspira spp. at 400× magnification. By sequencing, 53 cases could be assigned to the B. aalborgi lineage including "B. ibaraki" and "B. hominis", and 23 cases to B. pilosicoli. One case showed mixed colonization. The cases reported here reaffirm all major HIS Brachyspira spp. clusters already described. However, the phylogenetic diversity seems to be even greater than previously reported. In 14 cases, we could not confirm HIS by either FISH or PCR, but found colonization of the epithelium by rods and cocci, indicating misdiagnosis by histopathology. FISH in combination with molecular identification by 16S rRNA gene sequencing has proved to be a valuable addition to histopathology. It provides definite diagnosis of HIS and allows insights into phylogeny and distribution of Brachyspira spp. HIS should be considered as a differential diagnosis in diarrhea of unknown origin, particularly in patients from risk groups (e.g. patients with colonic adenomas, inflammatory polyps, inflammatory bowel disease or HIV infection and in men who have sex with men).

Fluorescence in situ hybridization for the identification of Treponema pallidum in tissue sections.

Syphilis is often called the great imitator because of its frequent atypical clinical manifestations that make the disease difficult to recognize. Because Treponema pallidum subsp. pallidum, the infectious agent of syphilis, is yet uncultivated in vitro, diagnosis is usually made using serology; however, in cases where serology is inconclusive or in patients with immunosuppression where these tests may be difficult to interpret, the availability of a molecular tool for direct diagnosis may be of pivotal importance. Here we present a fluorescence in situ hybridization (FISH) assay that simultaneously identifies and analyzes spatial distribution of T. pallidum in histological tissue sections. For this assay the species-specific FISH probe TPALL targeting the 16S rRNA of T. pallidum was designed in silico and evaluated using T. pallidum infected rabbit testicular tissue and a panel of non-syphilis spirochetes as positive and negative controls, respectively, before application to samples from four syphilis-patients. In a HIV positive patient, FISH showed the presence of T. pallidum in inguinal lymph node tissue. In a patient not suspected to suffer from syphilis but underwent surgery for phimosis, numerous T. pallidum cells were found in preputial tissue. In two cases with oral involvement, FISH was able to differentiate T. pallidum from oral treponemes and showed infection of the oral mucosa and tonsils, respectively. The TPALL FISH probe is now readily available for in situ identification of T. pallidum in selected clinical samples as well as T. pallidum research applications and animal models.

Eaf5/7/3 form a functionally independent NuA4 submodule linked to RNA polymerase II-coupled nucleosome recycling.

The NuA4 histone acetyltransferase complex is required for gene regulation, cell cycle progression, and DNA repair. Dissection of the 13-subunit complex reveals that the Eaf7 subunit bridges Eaf5 with Eaf3, a H3K36me3-binding chromodomain protein, and this Eaf5/7/3 trimer is anchored to NuA4 through Eaf5. This trimeric subcomplex represents a functional module, and a large portion exists in a native form outside the NuA4 complex. Gene-specific and genome-wide location analyses indicate that Eaf5/7/3 correlates with transcription activity and is enriched over the coding region. In agreement with a role in transcription elongation, the Eaf5/7/3 trimer interacts with phosphorylated RNA polymerase II and helps its progression. Loss of Eaf5/7/3 partially suppresses intragenic cryptic transcription arising in set2 mutants, supporting a role in nucleosome destabilization. On the other hand, loss of the trimer leads to an increase of replication-independent histone exchange over the coding region of transcribed genes. Taken together, these results lead to a model where Eaf5/7/3 associates with elongating polymerase to promote the disruption of nucleosomes in its path, but also their refolding in its wake.

Neuropeptidergic input pathways to the circadian pacemaker center of the Madeira cockroach analysed with an improved injection technique.

Light entrainment pathways synchronize the circadian clock of almost all species of the animal and plant kingdom to the daily light dark cycle. In the Madeira cockroach Rhyparobia (Leucophaea) maderae, the circadian clock is located in the accessory medulla of the brain's optic lobes. The clock has abundant neuropeptides with unknown functions. Previous studies suggested that myoinhibitory peptides (MIPs), orcokinins (ORCs), and allatotropin (AT) take part in light input pathways to the circadian clock. As the sequences of AT and ORCs of R. maderae have not yet been determined, with matrix-assisted laser desorption/ionization-time of flight mass spectrometry, the respective Rhyparobia peptides were characterized. To search for light-like phase-shifting inputs to the circadian clock, Rhyparobia-MIP-1, Rhyparobia-AT, and Rhyparobia-ORC were injected at different circadian times, combined with locomotor activity assays. An improved, less invasive injection method was developed that allowed for the analysis of peptide effects within <2 weeks after injection. Rhyparobia-MIP-1 and Rhyparobia-AT injections resulted in dose-dependent monophasic phase response curves with maximum delays at the beginning of the subjective night, similar to light-dependent phase delays. In contrast to Manduca sexta-AT, Rhyparobia-AT did not phase advance locomotor activity rhythms. Only injections of Rhyparobia-ORCs resulted in a biphasic light-like phase response curve. Thus, it is hypothesized that Rhyparobia-MIP-1 and -AT are candidates for relaying light-dependent delays and/or non-photic inputs to the clock, whereas Rhyparobia-ORCs might be part of the light-entrainment pathways relaying phase delays and advances to the circadian clock of the Madeira cockroach.

The lab oddity prevails: discovery of pan-CDK inhibitor (R)-S-cyclopropyl-S-(4-{[4-{[(1R,2R)-2-hydroxy-1-methylpropyl]oxy}-5-(trifluoromethyl)pyrimidin-2-yl]amino}phenyl)sulfoximide (BAY 1000394) for the treatment of cancer.

Lead optimization of a high-throughput screening hit led to the rapid identification of aminopyrimidine ZK 304709, a multitargeted CDK and VEGF-R inhibitor that displayed a promising preclinical profile. Nevertheless, ZK 304709 failed in phase I studies due to dose-limited absorption and high inter-patient variability, which was attributed to limited aqueous solubility and off-target activity against carbonic anhydrases. Further lead optimization efforts to address the off-target activity profile finally resulted in the introduction of a sulfoximine group, which is still a rather unusual approach in medicinal chemistry. However, the sulfoximine series of compounds quickly revealed very interesting properties, culminating in the identification of the nanomolar pan-CDK inhibitor BAY 1000394, which is currently being investigated in phase I clinical trials.

Histone H3K4 demethylation is negatively regulated by histone H3 acetylation in Saccharomyces cerevisiae.

Histone H3 lysine 4 trimethylation (H3K4me3) is a hallmark of transcription initiation, but how H3K4me3 is demethylated during gene repression is poorly understood. Jhd2, a JmjC domain protein, was recently identified as the major H3K4me3 histone demethylase (HDM) in Saccharomyces cerevisiae. Although JHD2 is required for removal of methylation upon gene repression, deletion of JHD2 does not result in increased levels of H3K4me3 in bulk histones, indicating that this HDM is unable to demethylate histones during steady-state conditions. In this study, we showed that this was due to the negative regulation of Jhd2 activity by histone H3 lysine 14 acetylation (H3K14ac), which colocalizes with H3K4me3 across the yeast genome. We demonstrated that loss of the histone H3-specific acetyltransferases (HATs) resulted in genome-wide depletion of H3K4me3, and this was not due to a transcription defect. Moreover, H3K4me3 levels were reestablished in HAT mutants following loss of JHD2, which suggested that H3-specific HATs and Jhd2 serve opposing functions in regulating H3K4me3 levels. We revealed the molecular basis for this suppression by demonstrating that H3K14ac negatively regulated Jhd2 demethylase activity on an acetylated peptide in vitro. These results revealed the existence of a general mechanism for removal of H3K4me3 following gene repression.

Imaging properties of small-pixel spectroscopic x-ray detectors based on cadmium telluride sensors.

Spectroscopic x-ray imaging by means of photon counting detectors has received growing interest during the past years. Critical to the image quality of such devices is their pixel pitch and the sensor material employed. This paper describes the imaging properties of Medipix2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with pixel pitches of 110 and 165 µm, which are in the order of the mean free path lengths of the characteristic x-rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two pixel pitches. The average number of pixels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two pixel pitches' abilities to discriminate between iodine and gadolinium contrast agents are examined. It is shown that the choice of the pixel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high x-ray fluxes and conclude with the finding that higher maximum count rates come at the cost of a reduced energy resolution.

Histone H3 lysine 36 methylation targets the Isw1b remodeling complex to chromatin.

Histone H3 lysine 36 methylation is a ubiquitous hallmark of productive transcription elongation. Despite the prevalence of this histone posttranslational modification, however, the downstream functions triggered by this mark are not well understood. In this study, we showed that H3K36 methylation promoted the chromatin interaction of the Isw1b chromatin-remodeling complex in Saccharomyces cerevisiae. Similar to H3K36 methylation, Isw1b was found at the mid- and 3' regions of transcribed genes genome wide, and its presence at active genes was dependent on H3K36 methylation and the PWWP domain of the Isw1b subunit, Ioc4. Moreover, purified Isw1b preferentially interacted with recombinant nucleosomes that were methylated at lysine 36, and this interaction also required the Ioc4 PWWP domain. While H3K36 methylation has been shown to regulate the binding of numerous factors, this is the first time that it has been shown to facilitate targeting of a chromatin-remodeling complex.

CHROMATRA: a Galaxy tool for visualizing genome-wide chromatin signatures.

UNLABELLED: CHROMATRA (CHROmatin Mapping Across TRAnscripts) is a visualization tool available as plug-in for the Galaxy platform. It allows detailed yet concise presentations of data derived from ChIP-chip or ChIP-seq experiments by visualizing enrichment scores across genes or other genomic features while accounting for their length and additional characteristics such as gene expression. It integrates into typical analysis workflows and enables rapid graphical assessment and comparison of genome-wide data at a glance. AVAILABILITY: https://github.com/cmmt/chromatra.

Myoinhibitory peptides in the brain of the cockroach Leucophaea maderae and colocalization with pigment-dispersing factor in circadian pacemaker cells.

Myoinhibitory peptides (MIPs) are a family of insect W(X(6))Wamides with inhibitory effects on visceral muscles and juvenile hormone synthesis. Although MIPs are widely distributed within the nervous system, a detailed analysis of their distribution and function in insect brains is still missing. We analyzed the distribution of MIPs in the brain of the cockroach Leucophaea maderae. We focused on the accessory medulla (AMe), a small neuropil near the medulla that acts as the master circadian clock. Matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) and Nano-LC electrospray ionization (ESI) mass spectrometry revealed five Lem-MIPs in preparations of the AMe and corpora cardiaca. The complete sequences of two of these peptides were identified. Immunocytochemistry revealed wide distribution of MIP-related peptides in the cockroach brain. The superior median protocerebrum, parts of the central complex, and the tritocerebrum showed particularly dense immunostaining. In contrast, only a few local interneurons were stained in the antennal lobe and a few extrinsic neurons in the mushroom body, including a giant neuron innervating the calyces. The noduli of the AMe showed dense immunostaining, and neurons in all AMe cell groups except the anterior neurons were labeled. Pigment-dispersing factor- (PDF) and MIP immunostaining was colocalized in two neurons of the AMe. No colocalization of MIP- and PDF immunostaining was detected in the anterior optic commissure, but two small PDF-immunoreactive commissural fibers near the posterior optic commissure showed colocalized MIP immunostaining. The results suggest that several MIPs participate in different functional circuits of the circadian system and are involved in multiple brain circuits of the Madeira cockroach.

Splitting the task: Ubp8 and Ubp10 deubiquitinate different cellular pools of H2BK123.

Monoubiquitination of H2BK123 (H2BK123ub), catalyzed by Rad6/Bre1, is a transient histone modification with roles in transcription and is essential for establishing H3K4 and H3K79 trimethylations (H3K4me3 and H3K79me3). Here, we investigated the chromatin network around H2BK123ub by examining its localization and co-occurrence with its dependent marks as well as the transcription elongation mark H3K36me3 across the genome of Saccharomyces cerevisiae. In yeast, H2BK123ub is removed by the deubiquitinases Ubp8 and Ubp10, but their genomic target regions remain to be determined. Genome-wide maps of H2BK123ub in the absence of Ubp8 and Ubp10 revealed their distinct target loci, which were genomic sites enriched for H3K4me3 and H3K79me3, respectively. We propose an extended model of the H2BK123ub cross-talk by integrating existing relationships with the substrate specificities of Ubp8 and Ubp10 reported here.

The specificity and topology of chromatin interaction pathways in yeast.

Packaging of DNA into chromatin has a profound impact on gene expression. To understand how changes in chromatin influence transcription, we analyzed 165 mutants of chromatin machinery components in Saccharomyces cerevisiae. mRNA expression patterns change in 80% of mutants, always with specific effects, even for loss of widespread histone marks. The data are assembled into a network of chromatin interaction pathways. The network is function based, has a branched, interconnected topology, and lacks strict one-to-one relationships between complexes. Chromatin pathways are not separate entities for different gene sets, but share many components. The study evaluates which interactions are important for which genes and predicts additional interactions, for example between Paf1C and Set3C, as well as a role for Mediator in subtelomeric silencing. The results indicate the presence of gene-dependent effects that go beyond context-dependent binding of chromatin factors and provide a framework for understanding how specificity is achieved through regulating chromatin.