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Items 3006 to 3010 of 3091 total

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  • The ribbon-helix-helix domain proteins CdrS and CdrL regulate cell division in archaea

    Darnell, C; Zheng, J; Wilson, S; Bertoli, R; Bisson-Filho, A; Garner, E; Schmid, A;
    Biology Department, Duke University, Durham, North Carolina, United States
    Product(s): Lovastatin
    Precise control of the cell cycle is central to the physiology of all cells. In prior work we demonstrated that archaeal cells maintain a constant size; however, the regulatory mechanisms underlying the cell cycle remain unexplored in this domain of life. Here we use genetics, functional genomics, and quantitative imaging to identify and characterize the novel CdrSL gene regulatory network in a model species of archaea. We demonstrate the central role of these ribbon-helix-helix family transcription factors in the regulation of cell division through specific transcriptional control of the gene encoding FtsZ2, a putative tubulin homolog. Using time lapse fluorescence microscopy in live cells cultivated in microfluidics devices, we further demonstrate that FtsZ2 is required for cell division but not elongation. The cdrS-ftsZ2 locus is highly conserved throughout the archaeal domain, and the central function of CdrS in regulating cell division is conserved across hypersaline adapted archaea. We propose that the CdrSL-FtsZ2 transcriptional network coordinates cell division timing with cell growth in archaea.ImportanceHealthy cell growth and division are critical for individual organism survival and species long-term viability. However, it remains unknown how cells of the domain Archaea maintain a healthy cell cycle. Understanding archaeal cell cycle is of paramount evolutionary importance given that an archaeal cell was the host of the endosymbiotic event that gave rise to eukaryotes. Here we identify and characterize novel molecular players needed for regulating cell division in archaea. These molecules dictate the timing of cell septation, but are dispensable for growth between divisions. Timing is accomplished through transcriptional control of the cell division ring. Our results shed light on mechanisms underlying the archaeal cell cycle, which has thus far remained elusive.
  • Lytic Reactivation of the Kaposi’s sarcoma-associated herpesvirus (KSHV) is Accompanied by Major Nucleolar Alterations

    Atari, N; Rajan, K; Chikne, V; Cohen-Chalamish, S; Orbaum, O; Jacob, A; Kalt, I; Michaeli, S; Sarid, R;
    The Mina and Everard Goodman Faculty of Life Sciences and Advanced Materials and Nanotechnology Institute, Bar Ilan University, Ramat-Gan, Israel
    The nucleolus is a sub-nuclear compartment whose primary function is the biogenesis of ribosomal subunits. Certain viral infections affect the morphology and composition of the nucleolar compartment and influence ribosomal RNA (rRNA) transcription and maturation. However, no description of nucleolar morphology and function during infection with Kaposi’s sarcoma-associated herpesvirus (KSHV) is available to date. Using immunofluorescence microscopy, we documented extensive destruction of the nuclear and nucleolar architecture during lytic reactivation of KSHV. This was manifested by redistribution of key nucleolar proteins, including the rRNA transcription factor, UBF, the essential pre-rRNA processing factor Fibrillarin, and the nucleolar multifunctional phosphoproteins Nucleophosmin (NPM1) and Nucleolin. Distinct delocalization patterns were evident; certain nucleolar proteins remained together whereas others dissociated, implying that nucleolar proteins undergo nonrandom programmed dispersion. Of note, neither Fibrillarin nor UBF colocalized with promyelocytic leukemia (PML) nuclear bodies or with the viral protein LANA-1, and their redistribution was not dependent on viral DNA replication or late viral gene expression. No significant changes in pre-rRNA levels and no accumulation of pre-rRNA intermediates were found by RT-qPCR and Northern blot analysis, respectively. Furthermore, fluorescent in situ hybridization (FISH), combined with immunofluorescence, revealed an overlap between Fibrillarin and internal transcribed spacer 1 (ITS1), which represents the primary product of the pre-rRNA, suggesting that the processing of rRNA proceeds during lytic reactivation. Finally, small changes in the levels of pseudouridylation were documented across the rRNA. Taken together, our results suggest that rRNA transcription and processing persist during lytic reactivation of KSHV, yet they may become uncoupled. Whether the observed nucleolar alterations favor productive infection or signify cellular anti-viral responses remains to be determined.Author SummaryWe describe the extensive destruction of the nuclear and nucleolar architecture during lytic reactivation of KSHV. Distinct delocalization patterns are illustrated: certain nucleolar proteins remained associated with each other whereas others dissociated, implying that nucleolar proteins undergo nonrandom programmed dispersion. Of note, no significant changes in pre-rRNA levels and no accumulation of pre-rRNA intermediates were found, suggesting that pre-RNA transcription and processing continue and could be uncoupled during lytic reactivation. Small changes in the levels of pseudouridylation were documented across the rRNA. Previous studies showed that the different forms of KSHV infection are controlled through cellular and viral functions, which reprogram host epigenetic, transcriptomic, post-transcriptomic and proteomic landscapes. The ability of KSHV to affect the nucleolus and rRNA modifications constitutes a novel interaction network between viral and cellular components. The study of rRNA modifications is still in its infancy; however, the notion of altering cell fate by regulating rRNA modifications has recently begun to emerge, and its significance in viral infection is intriguing.
  • PICK1 Controls Activity-Dependent Synaptic Vesicle Cargo Retrieval

    Yong, X; Cousin, M; Anggono, V;
    University of Queensland - Clem Jones Centre for Ageing Dementia Research
    Efficient retrieval of synaptic vesicles (SVs) is crucial to sustain synaptic transmission. PICK1 is a unique PDZ- and BAR-domain-containing protein that regulates the trafficking of postsynaptic glutamate receptors. It is also expressed in presynaptic terminals and is associated with the SVs; however, its role in regulating SV recycling remains unknown. Here we show that PICK1 loss of function selectively slows the kinetics of SV endocytosis in primary hippocampal neurons during high-frequency stimulation. PICK1 knockdown also causes surface stranding and mislocalization of the major SV protein synaptophysin along the axon. A functional PDZ domain of PICK1 and its interaction with the core endocytic protein AP-2 are required for the proper targeting and clustering of synaptophysin. We further show that PICK1, and its interaction with AP-2, are required for efficient SV endocytosis and sustained glutamate release. Our findings therefore identify PICK1 as a key regulator of presynaptic vesicle recycling in central synapses.
  • Microenvironmental changes by placenta-derived mesenchymal stem cells restore the ovarian function in ovariectomized rat via activated PI3K-FOXO3 pathway

    Choi, J; Seok, J; Lim, S; Kim, T; Kim, G;
    Gangneung-Wonju National University
    Background: Translational studies have explored the therapeutic potential and feasibility of mesenchymal stem cells (MSCs) in several degenerative diseases; however, the mechanistic studies of the function of these cells have been insufficient. As ovarian failures cause anovulation as well as ovarian steroid hormonal unbalances, the specific aims of this study were to analyze the therapeutic role of placenta derived MSCs (PD-MSCs) in an ovarian-failure ovariectomy (OVX) rat model and evaluate whether PD-MSCs transplantation (Tx) improved folliculogenesis and oocyte maturation in the injured ovary through PI3K/Akt and FOXO signaling. Methods: Blood and ovary tissue were collected and analyzed after various PD-MSCs Tx treatments in the ovariectomized rat model. Changes in the expression of folliculogenesis and ovary regeneration-related genes due to PD-MSCs treatments were analyzed by qRT-PCR, Western blotting, and histological analysis. Results: The levels of hormones related to ovary function were significantly increased in the PD-MSCs Tx groups compared with those of the non-transplantation group (NTx). The follicle numbers in the ovarian tissues were increased along with increased expression of genes related to folliculogenesis for PD-MSCs Tx compared with NTx groups. Furthermore, PD-MSCs Tx induced maturation of follicles by increasing the phosphorylation of GSK3 beta and FOXO3 (p<0.05) and shifting the balance of growth and apoptosis in the oocytes. Conclusions: Taken together, PD-MSCs Tx can restore the ovarian function as well as induce ovarian folliculogenesis via the PI3K/Akt and FOXO signaling pathway.
  • An Enteric Pathogen Subverts Colonization Resistance by Evading Competition for Amino Acids in the Gut

    Caballero-Flores, G; Pickard, JM; Fukuda, S; Inohara, N; Núñez, G
    Department of Pathology and Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
    The microbiota confers host protection by limiting the colonization of pathogenic bacteria in the gut, but the mechanisms by which pathogens overcome colonization resistance remain poorly understood. Using a high-density transposon screen in the enteric pathogen Citrobacter rodentium, we find that the bacterium requires amino acid biosynthesis pathways to colonize conventionally raised mice, but not germ-free or antibiotic-treated animals. These metabolic pathways are induced during infection by the presence of the gut microbiota. Reduced amounts of amino acids are found in the guts of conventionally raised mice compared with germ-free animals. Dietary administration of high protein increases amino acid levels in the gut and promotes pathogen colonization. Thus, the depletion of amino acids by the microbiota limits pathogen colonization, and in turn, the pathogen activates amino acid biosynthesis to expand in the presence of the microbiota.

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