27 results found
Khamri W, Abeles RD, Hou TZ, et al., 2017, Increased expression of CTLA4 by T cells, induced by B7 in sera, reduces adaptive immunity in patients with acute liver failure, Gastroenterology, Vol: 153, Pages: 263-276.e8, ISSN: 0016-5085
BACKGROUND & AIMS: Patients with acute liver failure (ALF) have defects in innate immune responses to microbes (immuneparesis) and are susceptible to sepsis. Cytotoxic T-lymphocyte associated protein 4 (CTLA4), which interacts with the membrane receptor B7 (also called CD80 and CD86), is a negative regulator of T-cell activation. We collected T cells from patients with ALF and investigated whether inhibitory signals downregulate adaptive immune responses in patients with ALF. METHODS: We collected peripheral blood mononuclear cells from patients with ALF and controls from September 2013 through September 2015 (45 patients with ALF, 20 patients with acute-on-chronic liver failure, 15 patients with cirrhosis with no evidence of acute decompensation, 20 patients with septic shock but no cirrhosis or liver disease, and 20 healthy individuals). Circulating CD4+T cells were isolated and analyzed by flow cytometry. CD4+ T cells were incubated with antigen, or agonist to CD3 and dendritic cells, with or without antibody against CTLA4; T-cell proliferation and protein expression were quantified. We measured levels of soluble B7 molecules in supernatants of isolated primary hepatocytes, hepatic sinusoidal endothelial cells, and biliary epithelial cells from healthy or diseased liver tissues. We also measured levels of soluble B7 serum samples from patients and controls, and mice with acetaminophen-induced liver injury using ELISAs. RESULTS: Peripheral blood samples from patients with ALF had a higher proportion of CD4+ CTLA4+ T cells than controls; patients with infections had the highest proportions. CD4+T cells from patients with ALF had a reduced proliferative response to antigen or CD3 stimulation compared to cells from controls; incubation of CD4+T cells from patients with ALF w
Amouroux R, Nashun B, Shirane K, et al., 2016, De novo DNA methylation drives 5hmC accumulation in mouse zygotes., Nature Cell Biology, Vol: 18, Pages: 225-233, ISSN: 1476-4679
Zygotic epigenetic reprogramming entails genome-wide DNA demethylation that is accompanied by Tet methylcytosine dioxygenase 3 (Tet3)-driven oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC; refs ,,,). Here we demonstrate using detailed immunofluorescence analysis and ultrasensitive LC-MS-based quantitative measurements that the initial loss of paternal 5mC does not require 5hmC formation. Small-molecule inhibition of Tet3 activity, as well as genetic ablation, impedes 5hmC accumulation in zygotes without affecting the early loss of paternal 5mC. Instead, 5hmC accumulation is dependent on the activity of zygotic Dnmt3a and Dnmt1, documenting a role for Tet3-driven hydroxylation in targeting de novo methylation activities present in the early embryo. Our data thus provide further insights into the dynamics of zygotic reprogramming, revealing an intricate interplay between DNA demethylation, de novo methylation and Tet3-driven hydroxylation.
Adhikari D, Diril MK, Busayavalasa K, et al., 2014, Mastl is required for timely activation of APC/C in meiosis I and Cdk1 reactivation in meiosis II, JOURNAL OF CELL BIOLOGY, Vol: 206, Pages: 843-853, ISSN: 0021-9525
Nabti I, Marangos P, Bormann J, et al., 2014, Dual-mode regulation of the APC/C by CDK1 and MAPK controls meiosis I progression and fidelity, The Journal of Cell Biology, Vol: 204, Pages: 891-900, ISSN: 0021-9525
Female meiosis is driven by the activities of two major kinases, cyclin-dependent kinase 1 (Cdk1) and mitogen-activated protein kinase (MAPK). To date, the role of MAPK in control of meiosis is thought to be restricted to maintaining metaphase II arrest through stabilizing Cdk1 activity. In this paper, we find that MAPK and Cdk1 play compensatory roles to suppress the anaphase-promoting complex/cyclosome (APC/C) activity early in prometaphase, thereby allowing accumulation of APC/C substrates essential for meiosis I. Furthermore, inhibition of MAPK around the onset of APC/C activity at the transition from meiosis I to meiosis II led to accelerated completion of meiosis I and an increase in aneuploidy at metaphase II. These effects appear to be mediated via a Cdk1/MAPK-dependent stabilization of the spindle assembly checkpoint, which when inhibited leads to increased APC/C activity. These findings demonstrate new roles for MAPK in the regulation of meiosis in mammalian oocytes.
Kuleszewicz K, Fu X, Kudo NR, 2013, Cohesin loading factor Nipbl localizes to chromosome axes during mammalian meiotic prophase, Cell Division, Vol: 8, Pages: 1-8, ISSN: 1747-1028
BackgroundSister chromatid cohesion mediated by the cohesin complex is essential for accurate chromosome segregation during mitosis and meiosis. Loading of cohesin onto chromosomes is dependent on another protein complex called kollerin, containing Nipbl/Scc2 and Mau2/Scc4. Nipbl is an evolutionarily conserved large protein whose haploinsufficiency in humans causes a developmental disorder called Cornelia de Lange syndrome. Although the function of Nipbl homologues for chromosome cohesion in meiotic cells of non-vertebrate models has been elucidated, Nipbl has not been characterized so far in mammalian spermatocytes or oocytes.FindingsHere we describe our analyses on the expression and localization of Nipbl in nuclei of mouse spermatocytes and oocytes at different stages of meiotic prophase. In both spermatocytes and oocytes we found that Nipbl is associated with the axial/lateral element of the synaptonemal complex (AE/LE) to which cohesin also localizes. Interestingly, Nipbl in spermatocytes, but not in oocytes, dissociates from the AE/LE at mid-pachytene stage coincident with completion of DNA double-strand break repair.ConclusionsOur data propose that cohesin loading activity is maintained during early stages of meiotic prophase in mammalian spermatocytes and oocytes.
Hussain S, Tuorto F, Menon S, et al., 2013, The Mouse Cytosine-5 RNA Methyltransferase NSun2 Is a Component of the Chromatoid Body and Required for Testis Differentiation, MOLECULAR AND CELLULAR BIOLOGY, Vol: 33, Pages: 1561-1570, ISSN: 0270-7306
Kim JH, Ishiguro KI, Kudo N, et al., 2013, Studying meiosis-specific cohesins in mouse embryonic oocytes, Methods in Molecular Biology, Vol: 957, Pages: 47-57, ISSN: 1064-3745
Distinct meiotic cohesin complexes play fundamental roles in various meiosis-specific chromosomal events in spatiotemporally different manners during mammalian meiotic prophase. Immunostaining is one of the essential methods to study meiotic cohesin dynamics. For the study of cohesins in the meiotic prophase of oocytes, ovaries should be taken from the embryos during a very limited period before birth. Here we focus on some technical tips concerning the preparation of oocyte chromosome spreads for immunostaining. Further, we describe a method for chromosome fluorescence in situ hybridization (FISH) against immunostained oocytes. © 2013 Springer Science+Business Media, LLC.
Kim JH, Ishiguro K, Kudo N, et al., 2013, Studying meiosis-specific cohesins in mouse embryonic oocytes, Methods Mol Biol, Vol: 957, Pages: 47-57, ISSN: 1064-3745
Distinct meiotic cohesin complexes play fundamental roles in various meiosis-specific chromosomal events in spatiotemporally different manners during mammalian meiotic prophase. Immunostaining is one of the essential methods to study meiotic cohesin dynamics. For the study of cohesins in the meiotic prophase of oocytes, ovaries should be taken from the embryos during a very limited period before birth. Here we focus on some technical tips concerning the preparation of oocyte chromosome spreads for immunostaining. Further, we describe a method for chromosome fluorescence in situ hybridization (FISH) against immunostained oocytes.
Tachibana-Konwalski K, Godwin J, van der Weyden L, et al., 2010, Rec8-containing cohesin maintains bivalents without turnover during the growing phase of mouse oocytes, GENES & DEVELOPMENT, Vol: 24, Pages: 2505-2516, ISSN: 0890-9369
Kudo NR, Anger M, Peters AHFM, et al., 2009, Role of cleavage by separase of the Rec8 kleisin subunit of cohesin during mammalian meiosis I, JOURNAL OF CELL SCIENCE, Vol: 122, Pages: 2686-2698, ISSN: 0021-9533
McGulnness BE, Anger M, Kouznetsova A, et al., 2009, Regulation of APC/C Activity in Oocytes by a Bub1-Dependent Spindle Assembly Checkpoint, CURRENT BIOLOGY, Vol: 19, Pages: 369-380, ISSN: 0960-9822
Kudo NR, Wassmann K, Anger M, et al., 2006, Resolution of chiasmata in oocytes requires separase-mediated proteolysis, CELL, Vol: 126, Pages: 135-146, ISSN: 0092-8674
Wirth KG, Wutz G, Kudo NR, et al., 2006, Separase: a universal trigger for sister chromatid disjunction but not chromosome cycle progression, The Journal of Cell Biology, Vol: 172, Pages: 847-860, ISSN: 0021-9525
Separase is a protease whose liberation from its inhibitory chaperone Securin triggers sister chromatid disjunction at anaphase onset in yeast by cleaving cohesin's kleisin subunit. We have created conditional knockout alleles of the mouse Separase and Securin genes. Deletion of both copies of Separase but not Securin causes embryonic lethality. Loss of Securin reduces Separase activity because deletion of just one copy of the Separase gene is lethal to embryos lacking Securin. In embryonic fibroblasts, Separase depletion blocks sister chromatid separation but does not prevent other aspects of mitosis, cytokinesis, or chromosome replication. Thus, fibroblasts lacking Separase become highly polyploid. Hepatocytes stimulated to proliferate in vivo by hepatectomy also become unusually large and polyploid in the absence of Separase but are able to regenerate functional livers. Separase depletion in bone marrow causes aplasia and the presumed death of hematopoietic cells other than erythrocytes. Destruction of sister chromatid cohesion by Separase may be a universal feature of mitosis in eukaryotic cells.
McGuinness BE, Hirota T, Kudo NR, et al., 2005, Shugoshin prevents dissociation of cohesin from centromeres during mitosis in vertebrate cells, PLoS Biology, Vol: 3, Pages: 433-449, ISSN: 1544-9173
Cohesion between sister chromatids is essential for their bi-orientation on mitotic spindles. It is mediated by a multisubunit complex called cohesin. In yeast, proteolytic cleavage of cohesin's α kleisin subunit at the onset of anaphase removes cohesin from both centromeres and chromosome arms and thus triggers sister chromatid separation. In animal cells, most cohesin is removed from chromosome arms during prophase via a separase-independent pathway involving phosphorylation of its Scc3-SA1/2 subunits. Cohesin at centromeres is refractory to this process and persists until metaphase, whereupon its α kleisin subunit is cleaved by separase, which is thought to trigger anaphase. What protects centromeric cohesin from the prophase pathway? Potential candidates are proteins, known as shugoshins, that are homologous to Drosophila MEI-S332 and yeast Sgo1 proteins, which prevent removal of meiotic cohesin complexes from centromeres at the first meiotic division. A vertebrate shugoshin-like protein associates with centromeres during prophase and disappears at the onset of anaphase. Its depletion by RNA interference causes HeLa cells to arrest in mitosis. Most chromosomes bi-orient on a metaphase plate, but precocious loss of centromeric cohesin from chromosomes is accompanied by loss of all sister chromatid cohesion, the departure of individual chromatids from the metaphase plate, and a permanent cell cycle arrest, presumably due to activation of the spindle checkpoint. Remarkably, expression of a version of Scc3-SA2 whose mitotic phosphorylation sites have been mutated to alanine alleviates the precocious loss of sister chromatid cohesion and the mitotic arrest of cells lacking shugoshin. These data suggest that shugoshin prevents phosphorylation of cohesin's Scc3-SA2 subunit at centromeres during mitosis. This ensures that cohesin persists at centromeres until activation of separase causes cleavage of its α kleisin subunit. Centromeric cohesion is one o
Wirth KG, Ricci R, Gimenez-Abian JF, et al., 2004, Loss of the anaphase-promoting complex in quiescent cells causes unscheduled hepatocyte proliferation, GENES & DEVELOPMENT, Vol: 18, Pages: 88-98, ISSN: 0890-9369
Murakami N, Ye Y, Kawanishi M, et al., 2002, New Rev-transport inhibitor with anti-HIV activity from Valerianae Radix, BIOORGANIC & MEDICINAL CHEMISTRY LETTERS, Vol: 12, Pages: 2807-2810, ISSN: 0960-894X
Hoshino H, Kobayashi A, Yoshida M, et al., 2000, Oxidative stress abolishes leptomycin B-sensitive nuclear export of transcription repressor Bach2 that counteracts activation of Maf recognition element, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 275, Pages: 15370-15376, ISSN: 0021-9258
Huang TT, Kudo N, Yoshida M, et al., 2000, A nuclear export signal in the N-terminal regulatory domain of I kappa B alpha controls cytoplasmic localization of inactive NF-kappa B/I kappa B alpha complexes, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 97, Pages: 1014-1019, ISSN: 0027-8424
Callanan M, Kudo N, Gout S, et al., 2000, Developmentally regulated activity of CRM1/XPO1 during early Xenopus embryogenesis, JOURNAL OF CELL SCIENCE, Vol: 113, Pages: 451-459, ISSN: 0021-9533
Kudo N, Matsumori N, Taoka H, et al., 1999, Leptomycin B inactivates CRM1/exportin 1 by covalent modification at a cysteine residue in the central conserved region, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 96, Pages: 9112-9117, ISSN: 0027-8424
Yoshida M, Kudo N, Horinouchi S, 1999, [Leptomycin: a specific inhibitor of protein nuclear export]., Tanpakushitsu Kakusan Koso, Vol: 44, Pages: 1379-1388, ISSN: 0039-9450
Kudo N, Taoka H, Toda T, et al., 1999, A novel nuclear export signal sensitive to oxidative stress in the fission yeast transcription factor Pap1, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 274, Pages: 15151-15158, ISSN: 0021-9258
Kudo N, Taoka H, Yoshida M, et al., 1999, Identification of a novel nuclear export signal sensitive to oxidative stress in yeast AP-1-like transcription factor, ANTICANCER MOLECULES: STRUCTURE, FUNCTION, AND DESIGN, Vol: 886, Pages: 204-207, ISSN: 0077-8923
Kudo N, Wolff B, Sekimoto T, et al., 1998, Leptomycin B inhibition of signal-mediated nuclear export by direct binding to CRM1, EXPERIMENTAL CELL RESEARCH, Vol: 242, Pages: 540-547, ISSN: 0014-4827
Kudo N, Khochbin S, Nishi K, et al., 1997, Molecular cloning and cell cycle-dependent expression of mammalian CRM1, a protein involved in nuclear export of proteins, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 272, Pages: 29742-29751, ISSN: 0021-9258
Kudo N, Kimura M, Beppu T, et al., 1995, Cloning and characterization of a gene involved in aerial mycelium formation in Streptomyces griseus., J Bacteriol, Vol: 177, Pages: 6401-6410, ISSN: 0021-9193
A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) is essentially required for aerial mycelium formation and streptomycin production in Streptomyces griseus. A DNA fragment which induced aerial mycelium formation and sporulation in an A-factor-deficient mutant strain, S. griseus HH1, was cloned from this strain on a high-copy-number plasmid. Subcloning and nucleotide sequencing revealed that one open reading frame with 218 amino acids, named AmfC, served as a multicopy suppressor of the aerial mycelium-defective phenotype of the A-factor-deficient strain. The amfC gene did not restore A-factor or streptomycin production, indicating that amfC is involved in aerial mycelium formation independently of secondary metabolic function. Disruption of the chromosomal amfC gene in the wild-type S. griseus strain caused a severe reduction in the abundance of spores but no effect on the shape or size of the spores. The infrequent sporulation of the amfC disruptant was reversed by introduction of amfC on a plasmid. The amfC-defective phenotype was also restored by the orf1590 gene but not by the amfR-amfA-amfB gene cluster. Nucleotide sequences homologous to the amfC gene were distributed in all of 12 Streptomyces species tested, including Streptomyces coelicolor A3(2). The amfC homolog of S. coelicolor A3(2) was cloned and its nucleotide sequence was determined. The AmfC products of S. griseus and S. coelicolor A3(2) showed a 60% identity in their amino acid sequences. Introduction of the amfC gene of S. coelicolor A3(2) into strain HH1 induced aerial mycelium formation and sporulation, which suggests that both play the same functional role in morphogenesis in the strains.
Kudo N, Ueda K, Ikeda H, et al., 1994, Plasmid-Mediated Gene Disruption in Streptomyces griseus., Actinomycetologica, Vol: 8, Pages: 17-20, ISSN: 0914-5818
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