• B-1-cell subpopulations contribute differently to gut immunity.

      Roy, Bishnudeo; Agarwal, Shiwani; Brennecke, Anne-Margarete; Krey, Martina; Pabst, Oliver; Düber, Sandra; Weiss, Siegfried; Molecular Immunology, Helmholtz Centre for Infection Research (HZI), Braunschweig, Germany. (2013-08)
      In mice, B-1 (B1a/B1b) cells are mainly located in the peritoneal cavity. B-1 cells are well known for their role in the early stages of Ab-mediated immune responses against pathogenic invasion as well as for the production of natural IgM antibodies. Although such B cells have been claimed to give rise to intestinal plasma cells producing IgA, a clear role of B-1 cells in IgA production in the gut-associated tissues is still not defined. Here, we employed the transgenic L2 mouse model characterized by the lack of B-2 cells and presence of B-1 cells as major B-cell subpopulation. The oligoclonality of the Ab repertoire in this mouse allowed us to take typical B1a cell VH sequences as indicators of the presence of IgM-producing B-1a cells in Peyer's patches as well as in lamina propria. However, amongst the IgAVH sequences recovered from the same tissues, none of the sequences showed B1a-cell specificity. Interestingly, all IgAVH sequences derived from the lamina propria of L2 mice displayed extensive numbers of nucleotide exchanges, indicating somatic hypermutation, and affinity maturation. This suggests that the contribution of natural unmutated IgA by B-1a cells to intestinal immunity is negligible.
    • Bacteria in Cancer Therapy: Renaissance of an Old Concept.

      Felgner, Sebastian; Kocijancic, Dino; Frahm, Michael; Weiss, Siegfried; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      The rising incidence of cancer cases worldwide generates an urgent need of novel treatment options. Applying bacteria may represent a valuable therapeutic variant that is intensively investigated nowadays. Interestingly, the idea to apply bacteria wittingly or unwittingly dates back to ancient times and was revived in the 19th century mainly by the pioneer William Coley. This review summarizes and compares the results of the past 150 years in bacteria mediated tumor therapy from preclinical to clinical studies. Lessons we have learned from the past provide a solid foundation on which to base future efforts. In this regard, several perspectives are discussed by which bacteria in addition to their intrinsic antitumor effect can be used as vector systems that shuttle therapeutic compounds into the tumor. Strategic solutions like these provide a sound and more apt exploitation of bacteria that may overcome limitations of conventional therapies.
    • BACTOME-a reference database to explore the sequence- and gene expression-variation landscape of Pseudomonas aeruginosa clinical isolates.

      Hornischer, Klaus; Khaledi, Ariane; Pohl, Sarah; Schniederjans, Monika; Pezoldt, Lorena; Casilag, Fiordiligie; Muthukumarasamy, Uthayakumar; Bruchmann, Sebastian; Thöming, Janne; Kordes, Adrian; et al. (2018-10-01)
      Extensive use of next-generation sequencing (NGS) for pathogen profiling has the potential to transform our understanding of how genomic plasticity contributes to phenotypic versatility. However, the storage of large amounts of NGS data and visualization tools need to evolve to offer the scientific community fast and convenient access to these data. We introduce BACTOME as a database system that links aligned DNA- and RNA-sequencing reads of clinical Pseudomonas aeruginosa isolates with clinically relevant pathogen phenotypes. The database allows data extraction for any single isolate, gene or phenotype as well as data filtering and phenotypic grouping for specific research questions. With the integration of statistical tools we illustrate the usefulness of a relational database structure for the identification of phenotype-genotype correlations as an essential part of the discovery pipeline in genomic research. Furthermore, the database provides a compilation of DNA sequences and gene expression values of a plethora of clinical isolates to give a consensus DNA sequence and consensus gene expression signature. Deviations from the consensus thereby describe the genomic landscape and the transcriptional plasticity of the species P. aeruginosa. The database is available at https://bactome.helmholtz-hzi.de.
    • BCL6--regulated by AhR/ARNT and wild-type MEF2B--drives expression of germinal center markers MYBL1 and LMO2.

      Ding, Jie; Dirks, Wilhelm G; Ehrentraut, Stefan; Geffers, Robert; MacLeod, Roderick A F; Nagel, Stefan; Pommerenke, Claudia; Romani, Julia; Scherr, Michaela; Vaas, Lea A I; et al. (2015-06)
      Genetic heterogeneity is widespread in tumors, but poorly documented in cell lines. According to immunoglobulin hypermutation analysis, the diffuse large B-cell lymphoma cell line U-2932 comprises two subpopulations faithfully representing original tumor subclones. We set out to identify molecular causes underlying subclone-specific expression affecting 221 genes including surface markers and the germinal center oncogenes BCL6 and MYC. Genomic copy number variations explained 58/221 genes differentially expressed in the two U-2932 clones. Subclone-specific expression of the aryl-hydrocarbon receptor (AhR) and the resulting activity of the AhR/ARNT complex underlaid differential regulation of 11 genes including MEF2B. Knock-down and inhibitor experiments confirmed that AhR/ARNT regulates MEF2B, a key transcription factor for BCL6. AhR, MEF2B and BCL6 levels correlated not only in the U-2932 subclones but in the majority of 23 cell lines tested, indicting overexpression of AhR as a novel mechanism behind BCL6 diffuse large B-cell lymphoma. Enforced modulation of BCL6 affected 48/221 signature genes. Although BCL6 is known as a transcriptional repressor, 28 genes were up-regulated, including LMO2 and MYBL1 which, like BCL6, signify germinal center diffuse large B-cell lymphoma. Supporting the notion that BCL6 can induce gene expression, BCL6 and the majority of potential targets were co-regulated in a series of B-cell lines. In conclusion, genomic copy number aberrations, activation of AhR/ARNT, and overexpression of BCL6 are collectively responsible for differential expression of more than 100 genes in subclones of the U-2932 cell line. It is particularly interesting that BCL6 - regulated by AhR/ARNT and wild-type MEF2B - may drive expression of germinal center markers in diffuse large B-cell lymphoma.
    • The BH3-only protein BID impairs the p38-mediated stress response and promotes hepatocarcinogenesis during chronic liver injury in mice.

      Orlik, Johanna; Schüngel, Sven; Buitrago-Molina, Laura Elisa; Marhenke, Silke; Geffers, Robert; Endig, Jessica; Lobschat, Katharina; Rössler, Stephanie; Goeppert, Benjamin; Manns, Michael P; et al. (2015-09)
      Apoptosis is critical for maintaining tissue homeostasis, and apoptosis evasion is considered as a hallmark of cancer. However, increasing evidence also suggests that proapoptotic molecules can contribute to the development of cancer, including liver cancer. The aim of this study was to further clarify the role of the proapoptotic B-cell lymphoma 2 homology domain 3 (BH3)-only protein BH3 interacting-domain death agonist (BID) for chronic liver injury (CLI) and hepatocarcinogenesis (HCG). Loss of BID significantly delayed tumor development in two mouse models of Fah-mediated and HBsTg-driven HCG, suggesting a tumor-promoting effect of BID. Liver injury as well as basal and mitogen-stimulated hepatocyte proliferation were not modulated by BID. Moreover, there was no in vivo or in vitro evidence that BID was involved in DNA damage response in hepatocytes and hepatoma cells. Our data revealed that CLI was associated with strong activation of oxidative stress (OS) response and that BID impaired full activation of p38 after OS.
    • The Biofilm Inhibitor Carolacton Enters Gram-Negative Cells: Studies Using a TolC-Deficient Strain of Escherichia coli.

      Donner, Jannik; Reck, Michael; Bunk, Boyke; Jarek, Michael; App, Constantin Benjamin; Meier-Kolthoff, Jan P; Overmann, Jörg; Müller, Rolf; Kirschning, Andreas; Wagner-Döbler, Irene; et al. (2017-11-01)
      The myxobacterial secondary metabolite carolacton inhibits growth of Streptococcus pneumoniae and kills biofilm cells of the caries- and endocarditis-associated pathogen Streptococcus mutans at nanomolar concentrations. Here, we studied the response to carolacton of an Escherichia coli strain that lacked the outer membrane protein TolC. Whole-genome sequencing of the laboratory E. coli strain TolC revealed the integration of an insertion element, IS5, at the tolC locus and a close phylogenetic relationship to the ancient E. coli K-12. We demonstrated via transcriptome sequencing (RNA-seq) and determination of MIC values that carolacton penetrates the phospholipid bilayer of the Gram-negative cell envelope and inhibits growth of E. coli TolC at similar concentrations as for streptococci. This inhibition is completely lost for a C-9 (R) epimer of carolacton, a derivative with an inverted stereocenter at carbon atom 9 [(S) → (R)] as the sole difference from the native molecule, which is also inactive in S. pneumoniae and S. mutans, suggesting a specific interaction of native carolacton with a conserved cellular target present in bacterial phyla as distantly related as Firmicutes and Proteobacteria. The efflux pump inhibitor (EPI) phenylalanine arginine β-naphthylamide (PAβN), which specifically inhibits AcrAB-TolC, renders E. coli susceptible to carolacton. Our data indicate that carolacton has potential for use in antimicrobial chemotherapy against Gram-negative bacteria, as a single drug or in combination with EPIs. Strain E. coli TolC has been deposited at the DSMZ; together with the associated RNA-seq data and MIC values, it can be used as a reference during future screenings for novel bioactive compounds. IMPORTANCE The emergence of pathogens resistant against most or all of the antibiotics currently used in human therapy is a global threat, and therefore the search for antimicrobials with novel targets and modes of action is of utmost importance. The myxobacterial secondary metabolite carolacton had previously been shown to inhibit biofilm formation and growth of streptococci. Here, we investigated if carolacton could act against Gram-negative bacteria, which are difficult targets because of their double-layered cytoplasmic envelope. We found that the model organism Escherichia coli is susceptible to carolacton, similar to the Gram-positive Streptococcus pneumoniae, if its multidrug efflux system AcrAB-TolC is either inactivated genetically, by disruption of the tolC gene, or physiologically by coadministering an efflux pump inhibitor. A carolacton epimer that has a different steric configuration at carbon atom 9 is completely inactive, suggesting that carolacton may interact with the same molecular target in both Gram-positive and Gram-negative bacteria.
    • Biofilms 2012: new discoveries and significant wrinkles in a dynamic field.

      Haussler, Susanne; Fuqua, Clay; Twincore, Center for Clinical and Experimental Infection Research, a joint venture of the Helmholtz Center of Infection Research, Braunschweig, and the Hannover Medical School, Hannover, Germany. (2013-07)
      The ASM 6th Conference on Biofilms was held in Miami, Florida, 29 September to 4 October, 2012. The conference provided an opportunity for the exchange of new findings and ideas with regard to biofilm research. A wide range of findings, spanning applied biology, evolution, ecology, physiology, and molecular biology, were presented at the conference. This review summarizes the presentations with regard to emerging biofilm-related themes.
    • Birth, evolution, and transmission of satellite-free mammalian centromeric domains.

      Nergadze, Solomon G; Piras, Francesca M; Gamba, Riccardo; Corbo, Marco; Cerutti, Federico; McCarter, Joseph G W; Cappelletti, Eleonora; Gozzo, Francesco; Harman, Rebecca M; Antczak, Douglas F; et al. (2018-01-01)
      Mammalian centromeres are associated with highly repetitive DNA (satellite DNA), which has so far hindered molecular analysis of this chromatin domain. Centromeres are epigenetically specified, and binding of the CENPA protein is their main determinant. In previous work, we described the first example of a natural satellite-free centromere on
    • Breaking the vicious cycle of antibiotic killing and regrowth of biofilm-residing .

      Müsken, Mathias; Pawar, Vinay; Schwebs, Timo; Bähre, Heike; Felgner, Sebastian; Weiss, Siegfried; Häussler, Susanne; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (2018-10-08)
      Biofilm-residing bacteria embedded in an extracellular matrix are protected from diverse physico-chemical insults. In addition to the general recalcitrance of biofilm-bacteria, high bacterial loads in biofilm-associated infections significantly diminishes the efficacy of antimicrobials due to a low per-cell antibiotic concentration. Accordingly, present antimicrobial treatment protocols, that have been established to serve the eradication of acute infections, fail to clear biofilm-associated chronic infections. In the present study, we applied automated confocal microscopy on Pseudomonas aeruginosa to monitor dynamic killing of biofilm-grown bacteria by tobramycin and colistin in real-time. We revealed that the time required for surviving bacteria to repopulate the biofilm could be taken as measure for effectiveness of the antimicrobial treatment. It depends on the: i) nature and concentration of the antibiotic, ii) duration of antibiotic treatment; iii) application as mono or combination therapy and iv) time intervals of drug administration. The vicious cycle of killing and repopulation of biofilm bacteria could also be broken in an in vivo model system by applying successive antibiotic dosages with time intervals that do not allow full reconstitution of the biofilm communities. Treatment regimens that consider the important aspects of antimicrobial killing kinetics bear the potential to improve control of biofilm regrowth. This is an important and underestimated factor that is bound to ensure sustainable treatment success of chronic infections.
    • CD25+ FoxP3+ Memory CD4 T Cells Are Frequent Targets of HIV Infection In Vivo.

      Chachage, Mkunde; Pollakis, Georgios; Kuffour, Edmund Osei; Haase, Kerstin; Bauer, Asli; Nadai, Yuka; Podola, Lilli; Clowes, Petra; Schiemann, Matthias; Henkel, Lynette; et al. (2016-10-15)
      Interleukin 2 (IL-2) signaling through the IL-2 receptor alpha chain (CD25) facilitates HIV replication in vitro and facilitates homeostatic proliferation of CD25(+) FoxP3(+) CD4(+) T cells. CD25(+) FoxP3(+) CD4(+) T cells may therefore constitute a suitable subset for HIV infection and plasma virion production. CD25(+) FoxP3(+) CD4(+) T cell frequencies, absolute numbers, and the expression of CCR5 and cell cycle marker Ki67 were studied in peripheral blood from HIV(+) and HIV(-) study volunteers. Different memory CD4(+) T cell subsets were then sorted for quantification of cell-associated HIV DNA and phylogenetic analyses of the highly variable EnvV1V3 region in comparison to plasma-derived virus sequences. In HIV(+) subjects, 51% (median) of CD25(+) FoxP3(+) CD4(+) T cells expressed the HIV coreceptor CCR5. Very high frequencies of Ki67(+) cells were detected in CD25(+) FoxP3(+) memory CD4(+) T cells (median, 27.6%) in comparison to CD25(-) FoxP3(-) memory CD4(+) T cells (median, 4.1%; P < 0.0001). HIV DNA content was 15-fold higher in CD25(+) FoxP3(+) memory CD4(+) T cells than in CD25(-) FoxP3(-) T cells (P = 0.003). EnvV1V3 sequences derived from CD25(+) FoxP3(+) memory CD4(+) T cells did not preferentially cluster with plasma-derived sequences. Quasi-identical cell-plasma sequence pairs were rare, and their proportion decreased with the estimated HIV infection duration. These data suggest that specific cellular characteristics of CD25(+) FoxP3(+) memory CD4(+) T cells might facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. The contribution of this cell population to plasma virion production remains unclear.
    • CD4 T Cell Dependent Colitis Exacerbation Following Re-Exposure of Mycobacterium avium ssp. paratuberculosis.

      Suwandi, Abdulhadi; Bargen, Imke; Pils, Marina C; Krey, Martina; Zur Lage, Susanne; Singh, Anurag K; Basler, Tina; Falk, Christine S; Seidler, Ursula; Hornef, Mathias W; et al. (2017)
      Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of Johne's disease (JD), a chronic inflammatory bowel disease of cattle characterized by intermittent to chronic diarrhea. In addition, MAP has been isolated from Crohn's disease (CD) patients. The impact of MAP on severity of clinical symptoms in JD as well as its role in CD are yet unknown. We have previously shown that MAP is able to colonize inflamed enteric tissue and to exacerbate the inflammatory tissue response (Suwandi et al., 2014). In the present study, we analyzed how repeated MAP administration influences the course of dextran sulfate sodium (DSS)-induced colitis. In comparison to mice exposed to DSS or MAP only, repeated exposure of DSS-treated mice to MAP (DSS/MAP) revealed a significantly enhanced clinical score, reduction of colon length as well as severe CD4(+) T cell infiltration into the colonic lamina propria. Functional analysis identified a critical role of CD4(+) T cells in the MAP-induced disease exacerbation. Additionally, altered immune responses were observed when closely related mycobacteria species such as M. avium ssp. avium and M. avium ssp. hominissuis were administered. These data reveal the specific ability of MAP to aggravate intestinal inflammation and clinical symptoms. Overall, this phenotype is compatible with similar disease promoting capabilites of MAP in JD and CD.
    • Cellular retinaldehyde-binding protein (CRALBP) is a direct downstream target of transcription factor Pax6.

      Boppana, Sridhar; Scheglov, Alexander; Geffers, Robert; Tarabykin, Victor; Max-Planck-Institute for Experimental Medicine, Hermann-Rein Strasse 3, 37075 Göttingen, Germany. boppansr@umdnj.edu (2012-02)
      Transcription factor Pax6 plays an essential role in the expression of other transcription factors, cell adhesion molecules and is crucial for neurogenesis in the developing forebrain. Analysis of gene expression profiles through microarray experiments in Pax6 mutants allowed us to focus on CRALBP, one of the many genes that were downregulated.
    • cGAS-STING-TBK1-IRF3/7 induced interferon-β contributes to the clearing of non tuberculous mycobacterial infection in mice.

      Ruangkiattikul, Nanthapon; Nerlich, Andreas; Abdissa, Ketema; Lienenklaus, Stefan; Suwandi, Abdulhadi; Janze, Nina; Laarmann, Kristin; Spanier, Julia; Kalinke, Ulrich; Weiss, Siegfried; et al. (2017-10-03)
      Type I interferons (IFN-I), such as IFN-α and IFN-β are important messengers in the host response against bacterial infections. Knowledge about the role of IFN-I in infections by nontuberculous mycobacteria (NTM) is limited. Here we show that macrophages infected with pathogens of the Mycobacterium avium complex produced significantly lower amounts of IFN-β than macrophages infected with the opportunistic pathogen M. smegmatis. To dissect the molecular mechanisms of this phenomenon, we focused on the obligate pathogen Mycobacterium avium ssp paratuberculosis (MAP) and the opportunistic M. smegmatis. Viability of both bacteria was required for induction of IFN-β in macrophages. Both bacteria induced IFN-β via the cGAS-STING-TBK1-IRF3/7-pathway of IFN-β activation. Stronger phosphorylation of TBK1 and higher amounts of extracellular bacterial DNA in the macrophage cytosol were found in M. smegmatis infected macrophages than in MAP infected macrophages. After intraperitoneal infection of mice, a strong Ifnb induction by M. smegmatis correlated with clearance of the bacteria. In contrast, MAP only induced weak Ifnb expression which correlated with bacterial persistence and increased number of granulomas in the liver. In mice lacking the type I interferon receptor we observed improved survival of M. smegmatis while survival of MAP was similar to that in wildtype mice. On the other hand, treatment of MAP infected wildtype mice with the IFN-I inducer poly(I:C) or recombinant IFN-β impaired the survival of MAP. This indicates an essential role of IFN-I in clearing infections by MAP and M. smegmatis. The expression level of IFN-I is decisive for transient versus persistent NTM infection.
    • Characterization of the p53 cistrome--DNA binding cooperativity dissects p53's tumor suppressor functions.

      Schlereth, Katharina; Heyl, Charlotte; Krampitz, Anna-Maria; Mernberger, Marco; Finkernagel, Florian; Scharfe, Maren; Jarek, Michael; Leich, Ellen; Rosenwald, Andreas; Stiewe, Thorsten; et al. (2013-08)
      p53 protects us from cancer by transcriptionally regulating tumor suppressive programs designed to either prevent the development or clonal expansion of malignant cells. How p53 selects target genes in the genome in a context- and tissue-specific manner remains largely obscure. There is growing evidence that the ability of p53 to bind DNA in a cooperative manner prominently influences target gene selection with activation of the apoptosis program being completely dependent on DNA binding cooperativity. Here, we used ChIP-seq to comprehensively profile the cistrome of p53 mutants with reduced or increased cooperativity. The analysis highlighted a particular relevance of cooperativity for extending the p53 cistrome to non-canonical binding sequences characterized by deletions, spacer insertions and base mismatches. Furthermore, it revealed a striking functional separation of the cistrome on the basis of cooperativity; with low cooperativity genes being significantly enriched for cell cycle and high cooperativity genes for apoptotic functions. Importantly, expression of high but not low cooperativity genes was correlated with superior survival in breast cancer patients. Interestingly, in contrast to most p53-activated genes, p53-repressed genes did not commonly contain p53 binding elements. Nevertheless, both the degree of gene activation and repression were cooperativity-dependent, suggesting that p53-mediated gene repression is largely indirect and mediated by cooperativity-dependently transactivated gene products such as CDKN1A, E2F7 and non-coding RNAs. Since both activation of apoptosis genes with non-canonical response elements and repression of pro-survival genes are crucial for p53's apoptotic activity, the cistrome analysis comprehensively explains why p53-induced apoptosis, but not cell cycle arrest, strongly depends on the intermolecular cooperation of p53 molecules as a possible safeguard mechanism protecting from accidental cell killing.
    • A chemical proteomics approach to identify c-di-GMP binding proteins in Pseudomonas aeruginosa.

      Düvel, Juliane; Bertinetti, Daniela; Möller, Stefan; Schwede, Frank; Morr, Michael; Wissing, Josef; Radamm, Lena; Zimmermann, Bastian; Genieser, Hans-Gottfried; Jänsch, Lothar; et al. (2012-02)
      In many bacteria, high levels of the ubiquitous second messenger c-di-GMP have been demonstrated to suppress motility and to promote the establishment of surface-adherent biofilm communities. While molecular mechanisms underlying the synthesis and degradation of c-di-GMP have been comprehensively characterized, little is known about how c-di-GMP mediates its regulatory effects. In this study, we have established a chemical proteomics approach to identify c-di-GMP interacting proteins in the opportunistic pathogen Pseudomonas aeruginosa. A functionalized c-di-GMP analog, 2'-aminohexylcarbamoyl-c-di-GMP (2'-AHC-c-di-GMP), was chemically synthesized and following its immobilization used to perform affinity pull down experiments. Enriched proteins were subsequently identified by high-resolution mass spectrometry. 2'-AHC-c-di-GMP was also employed in surface plasmon resonance studies to evaluate and quantify the interaction of c-di-GMP with its potential target molecules in vitro. The biochemical tools presented here may serve the identification of novel classes of c-di-GMP effectors and thus contribute to a better characterization and understanding of the complex c-di-GMP signaling network.
    • ChIP-on-chip analysis identifies IL-22 as direct target gene of ectopically expressed FOXP3 transcription factor in human T cells

      Jeron, Andreas; Hansen, Wiebke; Ewert, Franziska; Buer, Jan; Geffers, Robert; Bruder, Dunja (2012-12-17)
      Abstract Background The transcription factor (TF) forkhead box P3 (FOXP3) is constitutively expressed at high levels in naturally occurring CD4+CD25+ regulatory T cells (nTregs). It is not only the most accepted marker for that cell population but is also considered lineage determinative. Chromatin immunoprecipitation (ChIP) of TFs in combination with genomic tiling microarray analysis (ChIP-on-chip) has been shown to be an appropriate tool for identifying FOXP3 transcription factor binding sites (TFBSs) on a genome-wide scale. In combination with microarray expression analysis, the ChIP-on-chip technique allows identification of direct FOXP3 target genes. Results ChIP-on-chip analysis of the human FOXP3 expressed in resting and PMA/ionomycin–stimulated Jurkat T cells revealed several thousand putative FOXP3 binding sites and demonstrated the importance of intronic regions for FOXP3 binding. The analysis of expression data showed that the stimulation-dependent down-regulation of IL-22 was correlated with direct FOXP3 binding in the IL-22 promoter region. This association was confirmed by real-time PCR analysis of ChIP-DNA. The corresponding ChIP-region also contained a matching FOXP3 consensus sequence. Conclusions Knowledge of the general distribution patterns of FOXP3 TFBSs in the human genome under resting and activated conditions will contribute to a better understanding of this TF and its influence on direct target genes, as well as its importance for the phenotype and function of Tregs. Moreover, FOXP3-dependent repression of Th17-related IL-22 may be relevant to an understanding of the phenomenon of Treg/Th17 cell plasticity.
    • Chromatin binding of Gcn5 in Drosophila is largely mediated by CP190.

      Ali, Tamer; Krüger, Marcus; Bhuju, Sabin; Jarek, Michael; Bartkuhn, Marek; Renkawitz, Rainer; Hel,holtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-11-29)
      Centrosomal 190 kDa protein (CP190) is a promoter binding factor, mediates long-range interactions in the context of enhancer-promoter contacts and in chromosomal domain formation. All Drosophila insulator proteins bind CP190 suggesting a crucial role in insulator function. CP190 has major effects on chromatin, such as depletion of nucleosomes, high nucleosomal turnover and prevention of heterochromatin expansion. Here, we searched for enzymes, which might be involved in CP190 mediated chromatin changes. Eighty percent of the genomic binding sites of the histone acetyltransferase Gcn5 are colocalizing with CP190 binding. Depletion of CP190 reduces Gcn5 binding to chromatin. Binding dependency was further supported by Gcn5 mediated co-precipitation of CP190. Gcn5 is known to activate transcription by histone acetylation. We used the dCas9 system to target CP190 or Gcn5 to a Polycomb repressed and H3K27me3 marked gene locus. Both, CP190 as well as Gcn5, activate this locus, thus supporting the model that CP190 recruits Gcn5 and thereby activates chromatin.
    • Chromera velia, endosymbioses and the rhodoplex hypothesis--plastid evolution in cryptophytes, alveolates, stramenopiles, and haptophytes (CASH lineages).

      Petersen, Jörn; Ludewig, Ann-Kathrin; Michael, Victoria; Bunk, Boyke; Jarek, Michael; Baurain, Denis; Brinkmann, Henner (2014-03)
      The discovery of Chromera velia, a free-living photosynthetic relative of apicomplexan pathogens, has provided an unexpected opportunity to study the algal ancestry of malaria parasites. In this work, we compared the molecular footprints of a eukaryote-to-eukaryote endosymbiosis in C. velia to their equivalents in peridinin-containing dinoflagellates (PCD) to reevaluate recent claims in favor of a common ancestry of their plastids. To this end, we established the draft genome and a set of full-length cDNA sequences from C. velia via next-generation sequencing. We documented the presence of a single coxI gene in the mitochondrial genome, which thus represents the genetically most reduced aerobic organelle identified so far, but focused our analyses on five "lucky genes" of the Calvin cycle. These were selected because of their known support for a common origin of complex plastids from cryptophytes, alveolates (represented by PCDs), stramenopiles, and haptophytes (CASH) via a single secondary endosymbiosis with a red alga. As expected, our broadly sampled phylogenies of the nuclear-encoded Calvin cycle markers support a rhodophycean origin for the complex plastid of Chromera. However, they also suggest an independent origin of apicomplexan and dinophycean (PCD) plastids via two eukaryote-to-eukaryote endosymbioses. Although at odds with the current view of a common photosynthetic ancestry for alveolates, this conclusion is nonetheless in line with the deviant plastome architecture in dinoflagellates and the morphological paradox of four versus three plastid membranes in the respective lineages. Further support for independent endosymbioses is provided by analysis of five additional markers, four of them involved in the plastid protein import machinery. Finally, we introduce the "rhodoplex hypothesis" as a convenient way to designate evolutionary scenarios where CASH plastids are ultimately the product of a single secondary endosymbiosis with a red alga but were subsequently horizontally spread via higher-order eukaryote-to-eukaryote endosymbioses.
    • Clinical and Biological Manifestation of RNF168 Deficiency in Two Polish Siblings.

      Pietrucha, Barbara; Heropolitańska-Pliszka, Edyta; Geffers, Robert; Enßen, Julia; Wieland, Britta; Bogdanova, Natalia Valerijevna; Dörk, Thilo; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
      Germline mutations in the RING finger protein gene RNF168 have been identified in a combined immunodeficiency disorder called RIDDLE syndrome. Since only two patients have been described with somewhat different phenotypes, there is need to identify further patients. Here, we report on two Polish siblings with RNF168 deficiency due to homozygosity for a novel frameshift mutation, c.295delG, that was identified through exome sequencing. Both patients presented with immunoglobulin deficiency, telangiectasia, cellular radiosensitivity, and increased alpha-fetoprotein (AFP) levels. The younger sibling had a more pronounced neurological and morphological phenotype, and she also carried an ATM gene mutation in the heterozygous state. Immunoblot analyses showed absence of RNF168 protein, whereas ATM levels and function were proficient in lymphoblastoid cells from both patients. Consistent with the absence of RNF168 protein, 53BP1 recruitment to DNA double-strand breaks (DSBs) after irradiation was undetectable in lymphoblasts or primary fibroblasts from either of the two patients. γH2AX foci accumulated normally but they disappeared with significant delay, indicating a severe defect in DSB repair. A comparison with the two previously identified patients indicates immunoglobulin deficiency, cellular radiosensitivity, and increased AFP levels as hallmarks of RNF168 deficiency. The variability in its clinical expression despite similar cellular phenotypes suggests that some manifestations of RNF168 deficiency may be modified by additional genetic or epidemiological factors.
    • A clonotypic Vγ4Jγ1/Vδ5Dδ2Jδ1 innate γδ T-cell population restricted to the CCR6⁺CD27⁻ subset.

      Kashani, Elham; Föhse, Lisa; Raha, Solaiman; Sandrock, Inga; Oberdörfer, Linda; Koenecke, Christian; Suerbaum, Sebastian; Weiss, Siegfried; Prinz, Immo; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015)
      Here we investigate the TCR repertoire of mouse Vγ4(+) γδ T cells in correlation with their developmental origin and homeostasis. By deep sequencing we identify a high frequency of straight Vδ5Dδ2Jδ1 germline rearrangements without P- and N-nucleotides within the otherwise highly diverse Trd repertoire of Vγ4(+) cells. This sequence is infrequent in CCR6(-)CD27(+) cells, but abundant among CCR6(+)CD27(-) γδ T cells. Using an inducible Rag1 knock-in mouse model, we show that γδ T cells generated in the adult thymus rarely contain this germline-rearranged Vδ5Dδ2Jδ1 sequence, confirming its fetal origin. Single-cell analysis and deep sequencing of the Trg locus reveal a dominant CDR3 junctional motif that completes the TCR repertoire of invariant Vγ4(+)Vδ5(+) cells. In conclusion, this study identifies an innate subset of fetal thymus-derived γδ T cells with an invariant Vγ4(+)Vδ5(+) TCR that is restricted to the CCR6(+)CD27(-) subset of γδ T cells.