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Search Results: 1 - 10 of 400480 matches for " J?rg K?mper "
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The Mitochondrial LSU rRNA Group II Intron of Ustilago maydis Encodes an Active Homing Endonuclease Likely Involved in Intron Mobility
Anja Pfeifer, Bettina Martin, Jrg Kmper, Christoph W. Basse
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049551
Abstract: Background The a2 mating type locus gene lga2 is critical for uniparental mitochondrial DNA inheritance during sexual development of Ustilago maydis. Specifically, the absence of lga2 results in biparental inheritance, along with efficient transfer of intronic regions in the large subunit rRNA gene between parental molecules. However, the underlying role of the predicted LAGLIDADG homing endonuclease gene I-UmaI located within the group II intron LRII1 has remained unresolved. Methodology/Principal Findings We have investigated the enzymatic activity of I-UmaI in vitro based on expression of a tagged full-length and a naturally occurring mutant derivative, which harbors only the N-terminal LAGLIDADG domain. This confirmed Mg2+-dependent endonuclease activity and cleavage at the LRII1 insertion site to generate four base pair extensions with 3′ overhangs. Specifically, I-UmaI recognizes an asymmetric DNA sequence with a minimum length of 14 base pairs (5′-GACGGGAAGACCCT-3′) and tolerates subtle base pair substitutions within the homing site. Enzymatic analysis of the mutant variant indicated a correlation between the activity in vitro and intron homing. Bioinformatic analyses revealed that putatively functional or former functional I-UmaI homologs are confined to a few members within the Ustilaginales and Agaricales, including the phylogenetically distant species Lentinula edodes, and are linked to group II introns inserted into homologous positions in the LSU rDNA. Conclusions/Significance The present data provide strong evidence that intron homing efficiently operates under conditions of biparental inheritance in U. maydis. Conversely, uniparental inheritance may be critical to restrict the transmission of mobile introns. Bioinformatic analyses suggest that I-UmaI-associated introns have been acquired independently in distant taxa and are more widespread than anticipated from available genomic data.
A Novel High-Affinity Sucrose Transporter Is Required for Virulence of the Plant Pathogen Ustilago maydis
Ramon Wahl,Kathrin Wippel,Sarah Goos,Jrg Kmper,Norbert Sauer
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000303
Abstract: Plant pathogenic fungi cause massive yield losses and affect both quality and safety of food and feed produced from infected plants. The main objective of plant pathogenic fungi is to get access to the organic carbon sources of their carbon-autotrophic hosts. However, the chemical nature of the carbon source(s) and the mode of uptake are largely unknown. Here, we present a novel, plasma membrane-localized sucrose transporter (Srt1) from the corn smut fungus Ustilago maydis and its characterization as a fungal virulence factor. Srt1 has an unusually high substrate affinity, is absolutely sucrose specific, and allows the direct utilization of sucrose at the plant/fungal interface without extracellular hydrolysis and, thus, without the production of extracellular monosaccharides known to elicit plant immune responses. srt1 is expressed exclusively during infection, and its deletion strongly reduces fungal virulence. This emphasizes the central role of this protein both for efficient carbon supply and for avoidance of apoplastic signals potentially recognized by the host.
A Novel BAT3 Sequence Generated by Alternative RNA Splicing of Exon 11B Displays Cell Type-Specific Expression and Impacts on Subcellular Localization
Nadine Kmper, Jrg Kessler, Sebastian Temme, Claudia Wegscheid, Johannes Winkler, Norbert Koch
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035972
Abstract: Background The human lymphocyte antigen (HLA) encoded BAT3/BAG6 recently attracted interest as a regulator of protein targeting and degradation, a function that could be exerted in the cytosol and in the nucleus. The BAT3 gene was described to consist of 25 exons. Diversity of transcripts can be generated by alternative RNA splicing, which may control subcellular distribution of BAT3. Methodology/Principal Findings By cDNA sequencing we identified a novel alternatively spliced sequence of the BAT3 gene located between exons 11 and 12, which was designated as exon 11B. Using PCR and colony hybridization we identified six cDNA variants, which were produced by RNA splicing of BAT3 exons 5, 11B and 24. In four examined cell types the content of BAT3 splice variants was examined. Most of the cDNA clones from monocyte-derived dendritic cells contain exon 11B, whereas this sequence was almost absent in the B lymphoma Raji. Exon 5 was detected in most and exon 24 in approximately half of the cDNA clones. The subcellular distribution of endogenous BAT3 largely correlates with a cell type specific splicing pattern. In cells transfected with BAT3 variants, full-length and Δ24 BAT3 displayed nearly exclusive nuclear staining, whereas variants deleted of exon 11B showed substantial cytosolic expression. We show here that BAT3 is mainly expressed in the cytosol of Raji cells, while other cell types displayed both cytosolic and nuclear staining. Export of BAT3 from the nucleus to the cytosol is inhibited by treatment with leptomycin B, indicating that the Crm1 pathway is involved. Nuclear expression of BAT3 containing exon 11B suggests that this sequence plays a role for nuclear retention of the protein. Conclusions/Significance Cell type-specific subcellular expression of BAT3 suggests distinct functions in the cytosol and in the nucleus. Differential expression of BAT3 variants may reconcile the multiple roles described for BAT3.
A Novel High-Affinity Sucrose Transporter Is Required for Virulence of the Plant Pathogen Ustilago maydis
Ramon Wahl equal contributor,Kathrin Wippel equal contributor,Sarah Goos,Jrg Kmper ,Norbert Sauer
PLOS Biology , 2010, DOI: 10.1371/journal.pbio.1000303
Abstract: Plant pathogenic fungi cause massive yield losses and affect both quality and safety of food and feed produced from infected plants. The main objective of plant pathogenic fungi is to get access to the organic carbon sources of their carbon-autotrophic hosts. However, the chemical nature of the carbon source(s) and the mode of uptake are largely unknown. Here, we present a novel, plasma membrane-localized sucrose transporter (Srt1) from the corn smut fungus Ustilago maydis and its characterization as a fungal virulence factor. Srt1 has an unusually high substrate affinity, is absolutely sucrose specific, and allows the direct utilization of sucrose at the plant/fungal interface without extracellular hydrolysis and, thus, without the production of extracellular monosaccharides known to elicit plant immune responses. srt1 is expressed exclusively during infection, and its deletion strongly reduces fungal virulence. This emphasizes the central role of this protein both for efficient carbon supply and for avoidance of apoplastic signals potentially recognized by the host.
The SPF27 Homologue Num1 Connects Splicing and Kinesin 1-Dependent Cytoplasmic Trafficking in Ustilago maydis
Nikola Kellner,Kai Heimel,Theresa Obhof,Florian Finkernagel,Jrg Kmper
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004046
Abstract: The conserved NineTeen protein complex (NTC) is an integral subunit of the spliceosome and required for intron removal during pre-mRNA splicing. The complex associates with the spliceosome and participates in the regulation of conformational changes of core spliceosomal components, stabilizing RNA-RNA- as well as RNA-protein interactions. In addition, the NTC is involved in cell cycle checkpoint control, response to DNA damage, as well as formation and export of mRNP-particles. We have identified the Num1 protein as the homologue of SPF27, one of NTC core components, in the basidiomycetous fungus Ustilago maydis. Num1 is required for polarized growth of the fungal hyphae, and, in line with the described NTC functions, the num1 mutation affects the cell cycle and cell division. The num1 deletion influences splicing in U. maydis on a global scale, as RNA-Seq analysis revealed increased intron retention rates. Surprisingly, we identified in a screen for Num1 interacting proteins not only NTC core components as Prp19 and Cef1, but several proteins with putative functions during vesicle-mediated transport processes. Among others, Num1 interacts with the motor protein Kin1 in the cytoplasm. Similar phenotypes with respect to filamentous and polar growth, vacuolar morphology, as well as the motility of early endosomes corroborate the genetic interaction between Num1 and Kin1. Our data implicate a previously unidentified connection between a component of the splicing machinery and cytoplasmic transport processes. As the num1 deletion also affects cytoplasmic mRNA transport, the protein may constitute a novel functional interconnection between the two disparate processes of splicing and trafficking.
The Transcription Factor Rbf1 Is the Master Regulator for b-Mating Type Controlled Pathogenic Development in Ustilago maydis
Kai Heimel equal contributor,Mario Scherer equal contributor,Miroslav Vranes,Ramon Wahl,Chetsada Pothiratana,David Schuler,Volker Vincon,Florian Finkernagel,Ignacio Flor-Parra,Jrg Kmper
PLOS Pathogens , 2010, DOI: 10.1371/journal.ppat.1001035
Abstract: In the phytopathogenic basidiomycete Ustilago maydis, sexual and pathogenic development are tightly connected and controlled by the heterodimeric bE/bW transcription factor complex encoded by the b-mating type locus. The formation of the active bE/bW heterodimer leads to the formation of filaments, induces a G2 cell cycle arrest, and triggers pathogenicity. Here, we identify a set of 345 bE/bW responsive genes which show altered expression during these developmental changes; several of these genes are associated with cell cycle coordination, morphogenesis and pathogenicity. 90% of the genes that show altered expression upon bE/bW-activation require the zinc finger transcription factor Rbf1, one of the few factors directly regulated by the bE/bW heterodimer. Rbf1 is a novel master regulator in a multilayered network of transcription factors that facilitates the complex regulatory traits of sexual and pathogenic development.
p120ctn and P-Cadherin but Not E-Cadherin Regulate Cell Motility and Invasion of DU145 Prostate Cancer Cells
Sandra Kümper,Anne J. Ridley
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011801
Abstract: Adherens junctions consist of transmembrane cadherins, which interact intracellularly with p120ctn, ?-catenin and α-catenin. p120ctn is known to regulate cell-cell adhesion by increasing cadherin stability, but the effects of other adherens junction components on cell-cell adhesion have not been compared with that of p120ctn.
Ground-state properties of two-dimensional dimerized Heisenberg models
J. Sirker,A. Klümper,K. Hamacher
Physics , 2001, DOI: 10.1103/PhysRevB.65.134409
Abstract: The purpose of this paper is to investigate the ground-state properties of two-dimensional Heisenberg models on a square lattice with a given dimerization. Our aim is threefold: First, we want to investigate the dimensional transition from two to one dimension for three models consisting of weakly coupled chains for large dimerizations. Simple scaling arguments show that the interchain coupling is always relevant. The ground states of two of these models therefore have one-dimensional nature only at the decoupling point. The third considered model is more complicated, because it contains additional relevant intrachain couplings leading to a gap as shown by scaling arguments and numerical investigations. Second, we investigate at which point the dimerization destroys the N\'eel ordered ground state of the isotropic model. Within a mapping to a nonlinear sigma-model and linear spinwave theory (LSWT) we conclude that the stability of the N\'eel ordered state depends on the microscopic details of the model. Third, the considered models also can be regarded as effective models for a spin system with spin-phonon coupling. This leads to the question if a spin-Peierls transition, i.e. a gain of total energy due to lattice distortion, is possible. LSWT shows that such a transition is possible under certain conditions leading to a coexistence of long-range order and spin-Peierls dimerization. We also find that the gain of magnetic energy is largest for a stair-like distortion of the lattice.
ROSAT observations of PSR 2334+61 in the supernova remnant G114.3+0.3
W. Becker,K. T. S. Barzier,J. Trümper
Physics , 1995,
Abstract: We report on the observation of PSR 2334+61 in the soft X-ray domain with ROSAT. Assuming a power-law spectrum $dN/dE\propto E^{-\alpha}$ with photon-index $\alpha=2$ we derive an X-ray flux of $f_x=(7.1 \pm 0.2) \times 10^{-14} \hbox{erg s}^{-1}\hbox{cm}^{-2}$ within the $0.1$--$2.4$ keV energy range. An upper limit for the neutron star's surface temperature is put at $T_s^\infty \sim 1.2\times 10^6$ K for a neutron star with a medium stiff equation of state (FP-model with $M=1.4$ \Mo, $R=10.85$ km). Slightly different values for $T_s^\infty$ are computed for the various neutron star models available in the literature, reflecting differences in the equation of state. No soft X-ray emission is detected from the supernova remnant G114.3+0.3 associated with PSR 2334+61.
Spacetime diffeomorphisms and the geodesic approximation
Jürg K?ppeli
Physics , 2002,
Abstract: We present a spacetime diffeomorphism invariant formulation of the geodesic approximation to soliton dynamics.
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