• The Kaposi's sarcoma-associated herpesvirus (KSHV) non-structural membrane protein K15 is required for viral lytic replication and may represent a therapeutic target.

      Abere, Bizunesh; Mamo, Tamrat M; Hartmann, Silke; Samarina, Naira; Hage, Elias; Rückert, Jessica; Hotop, Sven-Kevin; Büsche, Guntram; Schulz, Thomas F; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-09)
      Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious cause of the highly vascularized tumor Kaposi's sarcoma (KS), which is characterized by proliferating spindle cells of endothelial origin, extensive neo-angiogenesis and inflammatory infiltrates. The KSHV K15 protein contributes to the angiogenic and invasive properties of KSHV-infected endothelial cells. Here, we asked whether K15 could also play a role in KSHV lytic replication. Deletion of the K15 gene from the viral genome or its depletion by siRNA lead to reduced virus reactivation, as evidenced by the decreased expression levels of KSHV lytic proteins RTA, K-bZIP, ORF 45 and K8.1 as well as reduced release of infectious virus. Similar results were found for a K1 deletion virus. Deleting either K15 or K1 from the viral genome also compromised the ability of KSHV to activate PLCγ1, Erk1/2 and Akt1. In infected primary lymphatic endothelial (LEC-rKSHV) cells, which have previously been shown to spontaneously display a viral lytic transcription pattern, transfection of siRNA against K15, but not K1, abolished viral lytic replication as well as KSHV-induced spindle cell formation. Using a newly generated monoclonal antibody to K15, we found an abundant K15 protein expression in KS tumor biopsies obtained from HIV positive patients, emphasizing the physiological relevance of our findings. Finally, we used a dominant negative inhibitor of the K15-PLCγ1 interaction to establish proof of principle that pharmacological intervention with K15-dependent pathways may represent a novel approach to block KSHV reactivation and thereby its pathogenesis.
    • Kaposi's sarcoma-associated herpesvirus viral interferon regulatory factor 4 (vIRF4/K10) is a novel interaction partner of CSL/CBF1, the major downstream effector of Notch signaling.

      Heinzelmann, Katharina; Scholz, Barbara A; Nowak, Agnes; Fossum, Even; Kremmer, Elisabeth; Haas, Juergen; Frank, Ronald; Kempkes, Bettina; Helmholtz Centre for infection research. Inhoffenstr. 7. 38124 Braunschweig, Germany. (2010-12)
      In cells infected with the Kaposi's sarcoma-associated herpesvirus (KSHV), CSL/CBF1 signaling is essential for viral replication and promotes the survival of KSHV-infected cells. CSL/CBF1 is a DNA adaptor molecule which recruits coactivator and corepressor complexes to regulate viral and cellular gene transcription and which is a major downstream effector molecule of activated Notch. The interaction of KSHV RTA and LANA with CSL/CBF1 has been shown to balance the lytic and latent viral life cycle. Here we report that a third KSHV protein, viral interferon regulatory factor 4 (vIRF4/K10), but none of the three other KSHV-encoded vIRFs, interacts with CSL/CBF1. Two regions of vIRF4 with dissimilar affinities contribute to CSL/CBF1 binding. Similar to Notch, vIRF4 targets the hydrophobic pocket in the beta trefoil domain of CSL/CBF1 through a short peptide motif which closely resembles a motif found in Notch but does not strictly follow the ΦWΦP consensus conserved in human and mouse Notch proteins. Our results suggest that vIRF4 might compete with Notch for CSL/CBF1 binding and signaling.
    • Kaposi's sarcoma-associated herpesvirus vIRF2 protein utilizes an IFN-dependent pathway to regulate viral early gene expression.

      Koch, Sandra; Damas, Modester; Freise, Anika; Hage, Elias; Dhingra, Akshay; Rückert, Jessica; Gallo, Antonio; Kremmer, Elisabeth; Tegge, Werner; Brönstrup, Mark; et al. (PLOS, 2019-05-01)
      Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) belongs to the subfamily of Gammaherpesvirinae and is the etiological agent of Kaposi's sarcoma as well as of two lymphoproliferative diseases: primary effusion lymphoma and multicentric Castleman disease. The KSHV life cycle is divided into a latent and a lytic phase and is highly regulated by viral immunomodulatory proteins which control the host antiviral immune response. Among them is a group of proteins with homology to cellular interferon regulatory factors, the viral interferon regulatory factors 1-4. The KSHV vIRFs are known as inhibitors of cellular interferon signaling and are involved in different oncogenic pathways. Here we characterized the role of the second vIRF protein, vIRF2, during the KSHV life cycle. We found the vIRF2 protein to be expressed in different KSHV positive cells with early lytic kinetics. Importantly, we observed that vIRF2 suppresses the expression of viral early lytic genes in both newly infected and reactivated persistently infected endothelial cells. This vIRF2-dependent regulation of the KSHV life cycle might involve the increased expression of cellular interferon-induced genes such as the IFIT proteins 1, 2 and 3, which antagonize the expression of early KSHV lytic proteins. Our findings suggest a model in which the viral protein vIRF2 allows KSHV to harness an IFN-dependent pathway to regulate KSHV early gene expression.
    • Labyrinthopeptins as virolytic inhibitors of respiratory syncytial virus cell entry.

      Blockus, Sebastian; Sake, Svenja M; Wetzke, Martin; Grethe, Christina; Graalmann, Theresa; Pils, Marina; Le Goffic, Ronan; Galloux, Marie; Prochnow, Hans; Rox, Katharina; et al. (Elsevier, 2020-03-18)
      Acute lower respiratory tract infections (ALRI) caused by respiratory syncytial virus (RSV) are associated with a severe disease burden among infants and elderly patients. Treatment options are limited. While numerous drug candidates with different viral targets are under development, the utility of RSV entry inhibitors is challenged by a low resistance barrier and by single mutations causing cross-resistance against a wide spectrum of fusion inhibitor chemotypes. We developed a cell-based screening assay for discovery of compounds inhibiting infection with primary RSV isolates. Using this system, we identified labyrinthopeptin A1 and A2 (Laby A1/A2), lantibiotics isolated from Actinomadura namibiensis, as effective RSV cell entry inhibitors with IC50s of 0.39 μM and 4.97 μM, respectively, and with favourable therapeutic index (>200 and > 20, respectively). Both molecules were active against multiple RSV strains including primary isolates and their antiviral activity against RSV was confirmed in primary human airway cells ex vivo and a murine model in vivo. Laby A1/A2 were antiviral in prophylactic and therapeutic treatment regimens and displayed synergistic activity when applied in combination with each other. Mechanistic studies showed that Laby A1/A2 exert virolytic activity likely by binding to phosphatidylethanolamine moieties within the viral membrane and by disrupting virus particle membrane integrity. Probably due to its specific mode of action, Laby A1/A2 antiviral activity was not affected by common resistance mutations to known RSV entry inhibitors. Taken together, Laby A1/A2 represent promising candidates for development as RSV inhibitors. Moreover, the cell-based screening system with primary RSV isolates described here should be useful to identify further antiviral agents.
    • Labyrinthopeptins exert broad-spectrum antiviral activity through lipid-binding-mediated virolysis.

      Prochnow, Hans; Rox, Katharina; Birudukota, N V Suryanarayana; Weichert, Loreen; Hotop, Sven-Kevin; Klahn, Philipp; Mohr, Kathrin; Franz, Sergej; Banda, Dominic H; Blockus, Sebastian; et al. (ASM, 2019-10-30)
      To counteract the serious health threat posed by known and novel viral pathogens, drugs that target a variety of viruses through a common mechanism have attracted recent attention due to their potential in treating (re-)emerging infections, for which direct acting antivirals are not available. We found that labyrinthopeptins A1 and A2, the prototype congeners of carbacyclic lanthipeptides, inhibit the proliferation of diverse enveloped viruses, including Dengue virus, Zika virus, West Nile virus, Hepatitis C virus, Chikungunya virus, Karposi's Sarcoma-associated Herpes virus, Cytomegalovirus, and Herpes Simplex virus, in the low μM to nM range. Mechanistic studies on viral particles revealed that labyrinthopeptins induce a virolytic effect through binding to the viral membrane lipid phosphatidylethanolamine (PE). These effects are enhanced by a combined equimolar application of both labyrinthopeptins, and a clear synergism was observed across a concentration range corresponding to IC10-IC90 values of the compounds. Time-resolved experiments with large unilamellar vesicles (LUVs) reveal that membrane lipid raft compositions (PC/PE/Chol/SM (17:10:33:40)) are particularly sensitive to labyrinthopeptins compared to PC/PE (90:10) LUVs, even though the overall PE-amount remains constant. Labyrinthopeptins exhibited low cytotoxicity and had favorable pharmacokinetic properties in mice (t1/2= 10.0 h), which designates them as promising antiviral compounds acting by an unusual viral lipid targeting mechanism.Importance For many viral infections, current treatment options are insufficient. Because the development of each antiviral drug is time-consuming and expensive, the prospect of finding broad-spectrum antivirals that can fight multiple, diverse viruses - well-known as well as (re-)emerging species - has gained attention, especially for the treatment of viral co-infections. While most known broad spectrum agents address processes in the host cell, we found that targeting lipids of the free virus outside the host cell with the natural products labyrinthopeptin A1 and A2 is a viable strategy to inhibit the proliferation of a broad range of viruses from different families, including Chikungunya virus, Dengue virus, Zika virus, Karposi's Sarcoma-associated Herpes virus, or Cytomegalovirus. Labyrinthopeptins bind to viral phosphatidylethanolamine and induce virolysis without exerting cytotoxicity to host cells. This represents a novel and unusual mechanism to tackle medically relevant viral infections.
    • LifeTime and improving European healthcare through cell-based interceptive medicine.

      Rajewsky, Nikolaus; Almouzni, Geneviève; Gorski, Stanislaw A; Aerts, Stein; Amit, Ido; Bertero, Michela G; Bock, Christoph; Bredenoord, Annelien L; Cavalli, Giacomo; Chiocca, Susanna; et al. (NPG, 2020-09-07)
      Here we describe the LifeTime Initiative, which aims to track, understand and target human cells during the onset and progression of complex diseases, and to analyse their response to therapy at single-cell resolution. This mission will be implemented through the development, integration and application of single-cell multi-omics and imaging, artificial intelligence and patient-derived experimental disease models during the progression from health to disease. The analysis of large molecular and clinical datasets will identify molecular mechanisms, create predictive computational models of disease progression, and reveal new drug targets and therapies. The timely detection and interception of disease embedded in an ethical and patient-centred vision will be achieved through interactions across academia, hospitals, patient associations, health data management systems and industry. The application of this strategy to key medical challenges in cancer, neurological and neuropsychiatric disorders, and infectious, chronic inflammatory and cardiovascular diseases at the single-cell level will usher in cell-based interceptive medicine in Europe over the next decade.
    • Mapping of NRF binding motifs of NF-kappaB p65 subunit.

      Reboll, Marc R; Schweda, Aike T; Bartels, Myriam; Franke, Raimo; Frank, Ronald; Nourbakhsh, Mahtab; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2011-11)
      NF-kappaB repressing factor (NRF) is a nuclear transcription factor that binds to a specific DNA sequence in NF-kappaB target promoters. Previous reports suggested that NRF interferes with the transcriptional activity of NF-kappaB binding sites through a direct interaction with NF-kappaB subunits. The aim of this study was to map specific NRF binding domains in the NF-kappaB proteins, p65 and p50. Our data demonstrate that NRF is able to interact with the p65 subunit and inhibit its transcription enhancing activity in reporter gene experiments. Using tandem affinity purifications (TAP), we show that NRF protein significantly binds to the endogenous p65, subunit but not to the p50 subunit. The selective binding activity of the NRF protein is consistently mediated by the N-terminal domain of NRF (Amino acids 1-380). Moreover, the Rel homology domain (RHD) of p65 is sufficient for binding to the N-terminal domain of NRF. Using detailed peptide mapping studies, we finally identify three peptide motifs in p65 RHD showing distinctive binding specificities for the NRF protein. According to the predicted structure of p65, all three peptide motifs align within an exposed region of p65 and might hint at promising targets for inhibitors.
    • Metabolome and transcriptome-wide effects of the carbon storage regulator A in enteropathogenic Escherichia coli.

      Berndt, Volker; Beckstette, Michael; Volk, Marcel; Dersch, Petra; Brönstrup, Mark; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Springer-Nature, 2019-01-15)
      The carbon storage regulator A (CsrA) is a conserved global regulatory system known to control central carbon pathways, biofilm formation, motility, and pathogenicity. The aim of this study was to characterize changes in major metabolic pathways induced by CsrA in human enteropathogenic Escherichia coli (EPEC) grown under virulence factor-inducing conditions. For this purpose, the metabolomes and transcriptomes of EPEC and an isogenic ∆csrA mutant derivative were analyzed by untargeted mass spectrometry and RNA sequencing, respectively. Of the 159 metabolites identified from untargeted GC/MS and LC/MS data, 97 were significantly (fold change ≥ 1.5; corrected p-value ≤ 0.05) regulated between the knockout and the wildtype strain. A lack of csrA led to an accumulation of fructose-6-phosphate (F6P) and glycogen synthesis pathway products, whereas metabolites in lower glycolysis and the citric acid cycle were downregulated. Associated pathways from the citric acid cycle like aromatic amino acid and siderophore biosynthesis were also negatively influenced. The nucleoside salvage pathways were featured by an accumulation of nucleosides and nucleobases, and a downregulation of nucleotides. In addition, a pronounced downregulation of lyso-lipid metabolites was observed. A drastic change in the morphology in the form of vesicle-like structures of the ∆csrA knockout strain was visible by electron microscopy. Colanic acid synthesis genes were strongly (up to 50 fold) upregulated, and the abundance of colanic acid was 3 fold increased according to a colorimetric assay. The findings expand the scope of pathways affected by the csrA regulon and emphasize its importance as a global regulator.
    • A Metabolomics Exploration of the Sexual Phase in the Marine Diatom Pseudo-nitzschia multistriata.

      Fiorini, Federica; Borgonuovo, Camilla; Ferrante, Maria Immacolata; Brönstrup, Mark; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-06-14)
      Pseudo-nitzschia multistriata is a planktonic marine diatom with a diplontic life cycle comprising a short sexual phase, during which gametes are produced following the encounter of two diploid cells of opposite mating type (MT). Gene expression studies have highlighted the presence of substantial changes occurring at the onset of sexual reproduction. Herein, we have hypothesized that the amount and nature of cellular metabolites varies along the mating process. To capture the metabolome of Pseudo-nitzschia multistriata at different harvesting times in an unbiased manner, we undertook an untargeted metabolomics approach based on liquid chromatography-tandem mass spectrometry. Using three different extraction steps, the method revealed pronounced differences in the metabolic profiles between control cells in the vegetative phase (MT+ and MT-) and mixed strains of opposite MTs (cross) undergoing sexual reproduction. Of the 2408 high-quality features obtained, 70 known metabolites could be identified based on in-house libraries and online databases; additional 46 features could be classified by molecular networking of tandem mass spectra. The reduction of phytol detected in the cross can be linked to the general downregulation of photosynthesis during sexual reproduction observed elsewhere. Moreover, the role of highly regulated compounds such as 7-dehydrodesmosterol, whose changes in abundance were the highest in the experiment, oleamide, ectoine, or trigonelline is discussed.
    • Minimum information about a protein affinity reagent (MIAPAR).

      Bourbeillon, Julie; Orchard, Sandra; Benhar, Itai; Borrebaeck, Carl; de Daruvar, Antoine; Dübel, Stefan; Frank, Ronald; Gibson, Frank; Gloriam, David; Haslam, Niall; et al. (2010-07)
    • Modification of uptake and subcellular distribution of doxorubicin by N-acylhydrazone residues as visualised by intrinsic fluorescence.

      Effenberger-Neidnicht, Katharina; Breyer, Sandra; Mahal, Katharina; Sasse, Florenz; Schobert, Rainer (2012-01)
      Doxorubicin (1) is commonly used in the treatment of a wide range of cancers. Some N-acylhydrazones of 1 were previously found to have an improved tumour and organ selectivity. In order to clarify the molecular basis for this effect, the cellular uptake into various cancer cells and the localisation in PtK(2) potoroo kidney cells of 1 and its N-acylhydrazones derived from heptadecanoic acid (2) and 11-(menthoxycarbonyl)undecanoic acid (3) were studied drawing on their intrinsic fluorescence.
    • A modular synthesis of tetracyclic meroterpenoid antibiotics

      Wildermuth, Raphael; Speck, Klaus; Haut, Franz-Lucas; Mayer, Peter; Karge, Bianka; Brönstrup, Mark; Magauer, Thomas; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany.
    • A multi-target caffeine derived rhodium(i) N-heterocyclic carbene complex: evaluation of the mechanism of action.

      Zhang, Jing-Jing; Muenzner, Julienne K; Abu El Maaty, Mohamed A; Karge, Bianka; Schobert, Rainer; Wölfl, Stefan; Ott, Ingo; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-08-16)
      A rhodium(i) and a ruthenium(ii) complex with a caffeine derived N-heterocyclic carbene (NHC) ligand were biologically investigated as organometallic conjugates consisting of a metal center and a naturally occurring moiety. While the ruthenium(ii) complex was largely inactive, the rhodium(i) NHC complex displayed selective cytotoxicity and significant anti-metastatic and in vivo anti-vascular activities and acted as both a mammalian and an E. coli thioredoxin reductase inhibitor. In HCT-116 cells it increased the reactive oxygen species level, leading to DNA damage, and it induced cell cycle arrest, decreased the mitochondrial membrane potential, and triggered apoptosis. This rhodium(i) NHC derivative thus represents a multi-target compound with promising anti-cancer potential.
    • Multiple antibody targets on herpes B glycoproteins B and D identified by screening sera of infected rhesus macaques with peptide microarrays.

      Hotop, Sven-Kevin; Abd El Wahed, Ahmed; Beutling, Ulrike; Jentsch, Dieter; Motzkus, Dirk; Frank, Ronald; Hunsmann, Gerhard; Stahl-Hennig, Christiane; Fritz, Hans-Joachim; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2014)
      Herpes B virus (or Herpesvirus simiae or Macacine herpesvirus 1) is endemic in many populations of macaques, both in the wild and in captivity. The virus elicits only mild clinical symptoms (if any) in monkeys, but can be transmitted by various routes, most commonly via bites, to humans where it causes viral encephalitis with a high mortality rate. Hence, herpes B constitutes a considerable occupational hazard for animal caretakers, veterinarians and laboratory personnel. Efforts are therefore being made to reduce the risk of zoonotic infection and to improve prognosis after accidental exposure. Among the measures envisaged are serological surveillance of monkey colonies and specific diagnosis of herpes B zoonosis against a background of antibodies recognizing the closely related human herpes simplex virus (HSV). 422 pentadecapeptides covering, in an overlapping fashion, the entire amino acid sequences of herpes B proteins gB and gD were synthesized and immobilized on glass slides. Antibodies present in monkey sera that bind to subsets of the peptide collection were detected by microserological techniques. With 42 different rhesus macaque sera, 114 individual responses to 18 different antibody target regions (ATRs) were recorded, 17 of which had not been described earlier. This finding may pave the way for a peptide-based, herpes B specific serological diagnostic test.
    • Multivalent Siderophore-DOTAM Conjugates as Theranostics for Imaging and Treatment of Bacterial Infections.

      Ferreira, Kevin; Hu, Hai-Yu; Fetz, Verena; Prochnow, Hans; Rais, Bushra; Müller, Peter P; Brönstrup, Mark; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-07-03)
      There is a strong need to better diagnose infections at deep body sites through noninvasive molecular imaging methods. Herein, we describe the synthesis and characterization of probes based on siderophore conjugates with catechol moieties and a central DOTAM scaffold. The probes can accommodate a metal ion as well as an antibiotic moiety and are therefore suited for theranostic purposes. The translocation of the conjugates across the outer and inner cell membranes of E. coli was confirmed by growth recovery experiments with enterobactin-deficient strains, by the antibacterial activity of ampicillin conjugates, and by confocal imaging using a fluorogen-activating protein-malachite green system adapted to E. coli. The suitability of the probes for in vivo imaging was demonstrated with a Cy5.5 conjugate in mice infected with P. aeruginosa.
    • Myxobacteria: natural pharmaceutical factories.

      Diez, Juana; Martinez, Javier P; Mestres, Jordi; Sasse, Florenz; Frank, Ronald; Meyerhans, Andreas; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2012)
      Myxobacteria are amongst the top producers of natural products. The diversity and unique structural properties of their secondary metabolites is what make these social microbes highly attractive for drug discovery. Screening of products derived from these bacteria has revealed a puzzling amount of hits against infectious and non-infectious human diseases. Preying mainly on other bacteria and fungi, why would these ancient hunters manufacture compounds beneficial for us? The answer may be the targeting of shared processes and structural features conserved throughout evolution.
    • The myxobacterial metabolite ratjadone A inhibits HIV infection by blocking the Rev/CRM1-mediated nuclear export pathway

      Fleta-Soriano, Eric; Martinez, Javier P; Hinkelmann, Bettina; Gerth, Klaus; Washausen, Peter; Diez, Juana; Frank, Ronald; Sasse, Florenz; Meyerhans, Andreas (2014-01-29)
      Abstract Background The nuclear export of unspliced and partially spliced HIV-1 mRNA is mediated by the recognition of a leucine-rich nuclear export signal (NES) in the HIV Rev protein by the host protein CRM1/Exportin1. This makes the CRM1-Rev complex an attractive target for the development of new antiviral drugs. Here we tested the anti-HIV efficacy of ratjadone A, a CRM1 inhibitor derived from myxobacteria. Results Ratjadone A inhibits HIV infection in vitro in a dose-dependent manner with EC50 values at the nanomolar range. The inhibitory effect of ratjadone A occurs around 12 hours post-infection and is specific for the Rev/CRM1-mediated nuclear export pathway. By using a drug affinity responsive target stability (DARTS) assay we could demonstrate that ratjadone A interferes with the formation of the CRM1-Rev-NES complex by binding to CRM1 but not to Rev. Conclusion Ratjadone A exhibits strong anti-HIV activity but low selectivity due to toxic effects. Although this limits its potential use as a therapeutic drug, further studies with derivatives of ratjadones might help to overcome these difficulties in the future.
    • The myxobacterial metabolite Soraphen A inhibits HIV-1 by reducing virus production and altering virion composition.

      Fleta-Soriano, Eric; Smutná, Katarína; Martinez, Javier P; Lorca Oró, Cristina; Sadiq, S Kashif; Mirambeau, Gilles; Lopez-Iglesias, Carmen; Bosch, Marta; Pol, Albert; Brönstrup, Mark; et al. (2017-05-22)
      Soraphen A is a myxobacterial metabolite that blocks the acetyl-CoA carboxylase of the host, and was previously identified as a novel HIV inhibitor. Here we report that Soraphen A acts by reducing virus production and altering the gp120 virion content, impacting entry capacity and infectivity. These effects are partially reversed by addition of palmitic acid, suggesting inhibition of HIV Env palmitoylation as one of the mechanisms of antiviral action.
    • Natural products targeting the elongation phase of eukaryotic protein biosynthesis.

      Brönstrup, Mark; Sasse, Florenz; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Royal Society of Chemistry, 2020-05-19)
      Covering: 2000 to 2020 The translation of mRNA into proteins is a precisely regulated, complex process that can be divided into three main stages, i.e. initiation, elongation, termination, and recycling. This contribution is intended to highlight how natural products interfere with the elongation phase of eukaryotic protein biosynthesis. Cycloheximide, isolated from Streptomyces griseus, has long been the prototype inhibitor of eukaryotic translation elongation. In the last three decades, a variety of natural products from different origins were discovered to also address the elongation step in different manners, including interference with the elongation factors eEF1 and eEF2 as well as binding to A-, P- or E-sites of the ribosome itself. Recent advances in the crystallization of the ribosomal machinery together with natural product inhibitors allowed characterizing similarities as well as differences in their mode of action. Since aberrations in protein synthesis are commonly observed in tumors, and malfunction or overexpression of translation factors can cause cellular transformation, the protein synthesis machinery has been realized as an attractive target for anticancer drugs. The therapeutic use of the first natural products that reached market approval, plitidepsin (Aplidin®) and homoharringtonine (Synribo®), will be introduced. In addition, we will highlight two other potential indications for translation elongation inhibitors, i.e. viral infections and genetic disorders caused by premature termination of translation.
    • New geldanamycin derivatives with anti Hsp properties by mutasynthesis.

      Hermane, Jekaterina; Eichner, Simone; Mancuso, Lena; Schröder, Benjamin; Sasse, Florenz; Zeilinger, Carsten; Kirschning, Andreas; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Royal Society of Chemistry, 2019-05-29)
      Mutasynthetic supplementation of the AHBA blocked mutant strain of S. hygroscopicus, the geldanamycin producer, with 21 aromatic and heteroaromatic amino acids provided new nonquinoid geldanamycin derivatives. Large scale (5 L) fermentation provided four new derivatives in sufficient quantity for full structural characterisation. Among these, the first thiophene derivative of reblastatin showed strong antiproliferative activity towards several human cancer cell lines. Additionally, inhibitory effects on human heat shock protein Hsp90α and bacterial heat shock protein from H. pylori HpHtpG were observed, revealing strong displacement properties for labelled ATP and demonstrating that the ATP-binding site of Hsps is the target site for the new geldanamycin derivatives.