Different roles of the human Orc6 protein in the replication initiation process.

In eukaryotes, binding of the six-subunit origin recognition complex (ORC) to DNA provides an interactive platform for the sequential assembly of pre-replicative complexes. This process licenses replication origins competent for the subsequent initiation step. Here, we analyze the contribution of human Orc6, the smallest subunit of ORC, to DNA binding and pre-replicative complex formation. We show that Orc6 not only interacts with Orc1-Orc5 but also with the initiation factor Cdc6. Biochemical and imaging experiments reveal that this interaction is required for licensing DNA replication competent. Furthermore, we demonstrate that Orc6 contributes to the interaction of ORC with the chaperone protein HMGA1a (high mobility group protein A1a). Binding of human ORC to replication origins is not specified at the level of DNA sequence and the functional organization of origins is poorly understood. We have identified HMGA1a as one factor that might direct ORC to AT-rich heterochromatic regions. The systematic analysis of the interaction between ORC and HMGA1a revealed that Orc6 interacts with the acidic C-terminus of HMGA1a and also with its AT-hooks. Both domains support autonomous replication if targeted to DNA templates. As such, Orc6 functions at different stages of the replication initiation process. Orc6 can interact with ORC chaperone proteins such as HMGA1a to facilitate chromatin binding of ORC and is also an essential factor for pre-RC formation

A multi-layered structure of the interphase chromocenter revealed by proximity-based biotinylation.

During interphase centromeres often coalesce into a small number of chromocenters, which can be visualized as distinct, DAPI dense nuclear domains. Intact chromocenters play a major role in maintaining genome stability as they stabilize the transcriptionally silent state of repetitive DNA while ensuring centromere function. Despite its biological importance, relatively little is known about the molecular composition of the chromocenter or the processes that mediate chromocenter formation and maintenance. To provide a deeper molecular insight into the composition of the chromocenter and to demonstrate the usefulness of proximity-based biotinylation as a tool to investigate those questions, we performed super resolution microscopy and proximity-based biotinylation experiments of three distinct proteins associated with the chromocenter in Drosophila. Our work revealed an intricate internal architecture of the chromocenter suggesting a complex multilayered structure of this intranuclear domain

Tumor Rejection Induced by CD70-mediated Quantitative and Qualitative Effects on Effector CD8+ T Cell Formation

In vivo priming of antigen-specific CD8(+) T cells results in their expansion and differentiation into effector T cells followed by contraction into a memory T cell population that can be maintained for life. Recent evidence suggests that after initial antigenic stimulation, the magnitude and kinetics of the CD8(+) T cell response are programmed. However, it is unclear to what extent CD8(+) T cell instruction in vivo is modulated by costimulatory signals. Here, we demonstrate that constitutive ligation of the tumor necrosis factor receptor family member CD27 by its ligand CD70 quantitatively augments CD8(+) T cell responses to influenza virus infection and EL-4 tumor challenge in vivo by incrementing initial expansion and maintaining higher numbers of antigen-specific T cells in the memory phase. Concomitantly, the quality of antigen-specific T cells improved as evidenced by increased interferon (IFN)-γ production and a greater cytotoxic potential on a per cell basis. As an apparent consequence, the superior effector T cell formation induced by CD70 protected against a lethal dose of poorly immunogenic EL4 tumor cells in a CD8(+) T cell– and IFN-γ–dependent manner. Thus, CD70 costimulation enhances both the expansion and per cell activity of antigen-specific CD8(+) T cells

Syllabus Hoogwater 1995, voordrachten Symposium Hoogwater

Door de CUR en TAW georganiseerd symposium naar aanleiding van het rivierhoogwater van 1995 en de maatregelen die toen getroffen zijn, alsmede het wetsvoorstel voor aanpassing van de Wet op de Waterkering. Onderdelen zijn: "WAS HET HOOGWATER HOOG?" - VOORLOPIGE ANALYSE HOOGWATERPERIODE JANUARI-FEBRUARI 1995 - HOOGWATER IN WATERSCHAP ROER EN OVERMAAS - GEDRAG VAN NOODVOORZIENINGEN TIJDENS HET HOOGWATER - BOERTIEN TEGEN HET LICHT VAN HET HOOGWATER 1995 - FALEN VAN DIJKEN - INTEGRALE BENADERING VAN HET RIVIERENGEBIED - ELFSTEDENTOCHT EN DELTAPLAN GROTE RIVIEREN - VERSNELDE AANPAK IN DE PRAKTIJK - Wetsvoorstel "Deltawet grote riviere