1
|
Avril M, Brazier AJ, Melcher M, Sampath S, Smith JD. DC8 and DC13 var genes associated with severe malaria bind avidly to diverse endothelial cells. PLoS Pathog 2013; 9:e1003430. [PMID: 23825944 PMCID: PMC3694856 DOI: 10.1371/journal.ppat.1003430] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 04/30/2013] [Indexed: 11/25/2022] Open
Abstract
During blood stage infection, Plasmodium falciparum infected erythrocytes (IE) bind to host blood vessels. This virulence determinant enables parasites to evade spleen-dependent killing mechanisms, but paradoxically in some cases may reduce parasite fitness by killing the host. Adhesion of infected erythrocytes is mediated by P. falciparum erythrocyte membrane protein 1 (PfEMP1), a family of polymorphic adhesion proteins encoded by var genes. Whereas cerebral binding and severe malaria are associated with parasites expressing DC8 and DC13 var genes, relatively little is known about the non-brain endothelial selection on severe malaria adhesive types. In this study, we selected P. falciparum-IEs on diverse endothelial cell types and demonstrate that DC8 and DC13 var genes were consistently among the major var transcripts selected on non-brain endothelial cells (lung, heart, bone marrow). To investigate the molecular basis for this avid endothelial binding activity, recombinant proteins were expressed from the predominant upregulated DC8 transcript, IT4var19. In-depth binding comparisons revealed that multiple extracellular domains from this protein bound brain and non-brain endothelial cells, and individual domains largely did not discriminate between different endothelial cell types. Additionally, we found that recombinant DC8 and DC13 CIDR1 domains exhibited a widespread endothelial binding activity and could compete for DC8-IE binding to brain endothelial cells, suggesting they may bind the same host receptor. Our findings provide new insights into the interaction of severe malaria adhesive types and host blood vessels and support the hypothesis that parasites causing severe malaria express PfEMP1 variants with a superior ability to adhere to diverse endothelial cell types, and may therefore endow these parasites with a growth and transmission advantage.
Collapse
Affiliation(s)
- Marion Avril
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Andrew J. Brazier
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Martin Melcher
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Sowmya Sampath
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Joseph D. Smith
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
| |
Collapse
|
2
|
Sampath S, Carrico C, Janes J, Gurumoorthy S, Gibson C, Melcher M, Chitnis CE, Wang R, Schief WR, Smith JD. Glycan masking of Plasmodium vivax Duffy Binding Protein for probing protein binding function and vaccine development. PLoS Pathog 2013; 9:e1003420. [PMID: 23853575 PMCID: PMC3681752 DOI: 10.1371/journal.ppat.1003420] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 04/30/2013] [Indexed: 11/19/2022] Open
Abstract
Glycan masking is an emerging vaccine design strategy to focus antibody responses to specific epitopes, but it has mostly been evaluated on the already heavily glycosylated HIV gp120 envelope glycoprotein. Here this approach was used to investigate the binding interaction of Plasmodium vivax Duffy Binding Protein (PvDBP) and the Duffy Antigen Receptor for Chemokines (DARC) and to evaluate if glycan-masked PvDBPII immunogens would focus the antibody response on key interaction surfaces. Four variants of PVDBPII were generated and probed for function and immunogenicity. Whereas two PvDBPII glycosylation variants with increased glycan surface coverage distant from predicted interaction sites had equivalent binding activity to wild-type protein, one of them elicited slightly better DARC-binding-inhibitory activity than wild-type immunogen. Conversely, the addition of an N-glycosylation site adjacent to a predicted PvDBP interaction site both abolished its interaction with DARC and resulted in weaker inhibitory antibody responses. PvDBP is composed of three subdomains and is thought to function as a dimer; a meta-analysis of published PvDBP mutants and the new DBPII glycosylation variants indicates that critical DARC binding residues are concentrated at the dimer interface and along a relatively flat surface spanning portions of two subdomains. Our findings suggest that DARC-binding-inhibitory antibody epitope(s) lie close to the predicted DARC interaction site, and that addition of N-glycan sites distant from this site may augment inhibitory antibodies. Thus, glycan resurfacing is an attractive and feasible tool to investigate protein structure-function, and glycan-masked PvDBPII immunogens might contribute to P. vivax vaccine development. An important goal of many vaccine efforts is to inhibit pathogen invasion of host cells, but few approaches exist to target vaccine antibodies on invasion blocking epitopes. Glycan masking is a vaccine design strategy to hide protein surfaces with carbohydrates and focus antibodies on exposed surfaces. This approach has mostly been evaluated on the heavily glycosylated HIV envelope glycoprotein, but it has never been tested on eukaryotic pathogens, such as Plasmodium, which have limited N-glycosylation machinery and therefore may provide a better platform to explore this strategy. Here, we used glycan masking to investigate the binding interaction between Plasmodium vivax Duffy binding protein (PvDBP) and the Duffy Antigen Receptor for Chemokines (DARC). This study showed that addition of an N-glycan site in a predicted host interaction surface abolished binding and potentially covered up an inhibitory antibody epitope. In contrast, addition of multiple N-glycan sites distant from predicted interaction surfaces did not inhibit binding but did slightly enhance elicitation of inhibitory antibodies. This analysis shows that glycan resurfacing offers an integrated approach to characterize protein function and immunogenicity and that glycan resurfacing of PvDBPII immunogens may have utility in P. vivax-malaria vaccine development.
Collapse
Affiliation(s)
- Sowmya Sampath
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Chris Carrico
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Joel Janes
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Sairam Gurumoorthy
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Claire Gibson
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Martin Melcher
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Chetan E. Chitnis
- International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Ruobing Wang
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - William R. Schief
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Department of Immunology and Microbial Science and IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, California, United States of America
- Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail: (WRS); (JDS)
| | - Joseph D. Smith
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
- Department of Pathobiology, University of Washington, Seattle, Washington, United States of America
- * E-mail: (WRS); (JDS)
| |
Collapse
|
3
|
McMillan PJ, Millet C, Batinovic S, Maiorca M, Hanssen E, Kenny S, Muhle RA, Melcher M, Fidock DA, Smith JD, Dixon MWA, Tilley L. Spatial and temporal mapping of the PfEMP1 export pathway in Plasmodium falciparum. Cell Microbiol 2013; 15:1401-18. [PMID: 23421990 DOI: 10.1111/cmi.12125] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 02/01/2013] [Accepted: 02/07/2013] [Indexed: 01/24/2023]
Abstract
The human malaria parasite, Plasmodium falciparum, modifies the red blood cells (RBCs) that it infects by exporting proteins to the host cell. One key virulence protein, P. falciparum Erythrocyte Membrane Protein-1 (PfEMP1), is trafficked to the surface of the infected RBC, where it mediates adhesion to the vascular endothelium. We have investigated the organization and development of the exomembrane system that is used for PfEMP1 trafficking. Maurer's cleft cisternae are formed early after invasion and proteins are delivered to these (initially mobile) structures in a temporally staggered and spatially segregated manner. Membrane-Associated Histidine-Rich Protein-2 (MAHRP2)-containing tether-like structures are generated as early as 4 h post invasion and become attached to Maurer's clefts. The tether/Maurer's cleft complex docks onto the RBC membrane at ~20 h post invasion via a process that is not affected by cytochalasin D treatment. We have examined the trafficking of a GFP chimera of PfEMP1 expressed in transfected parasites. PfEMP1B-GFP accumulates near the parasite surface, within membranous structures exhibiting a defined ultrastructure, before being transferred to pre-formed mobile Maurer's clefts. Endogenous PfEMP1 and PfEMP1B-GFP are associated with Electron-Dense Vesicles that may be responsible for trafficking PfEMP1 from the Maurer's clefts to the RBC membrane.
Collapse
Affiliation(s)
- Paul J McMillan
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria, Australia
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Janes JH, Wang CP, Levin-Edens E, Vigan-Womas I, Guillotte M, Melcher M, Mercereau-Puijalon O, Smith JD. Investigating the host binding signature on the Plasmodium falciparum PfEMP1 protein family. PLoS Pathog 2011; 7:e1002032. [PMID: 21573138 PMCID: PMC3088720 DOI: 10.1371/journal.ppat.1002032] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 03/01/2011] [Indexed: 12/03/2022] Open
Abstract
The Plasmodium falciparum erythrocyte membrane protein 1
(PfEMP1) family plays a central role in antigenic variation and cytoadhesion of
P. falciparum infected erythrocytes. PfEMP1
proteins/var genes are classified into three main
subfamilies (UpsA, UpsB, and UpsC) that are hypothesized to have different roles
in binding and disease. To investigate whether these subfamilies have diverged
in binding specificity and test if binding could be predicted by adhesion domain
classification, we generated a panel of 19 parasite lines that primarily
expressed a single dominant var transcript and assayed binding
against 12 known host receptors. By limited dilution cloning, only UpsB and UpsC
var genes were isolated, indicating that UpsA
var gene expression is rare under in vitro
culture conditions. Consequently, three UpsA variants were obtained by rosette
purification and selection with specific monoclonal antibodies to create a more
representative panel. Binding assays showed that CD36 was the most common
adhesion partner of the parasite panel, followed by ICAM-1 and TSP-1, and that
CD36 and ICAM-1 binding variants were highly predicted by adhesion domain
sequence classification. Binding to other host receptors, including CSA, VCAM-1,
HABP1, CD31/PECAM, E-selectin, Endoglin, CHO receptor “X”, and
Fractalkine, was rare or absent. Our findings identify a category of larger
PfEMP1 proteins that are under dual selection for ICAM-1 and CD36 binding. They
also support that the UpsA group, in contrast to UpsB and UpsC
var genes, has diverged from binding to the major
microvasculature receptor CD36 and likely uses other mechanisms to sequester in
the microvasculature. These results demonstrate that CD36 and ICAM-1 have left
strong signatures of selection on the PfEMP1 family that can be detected by
adhesion domain sequence classification and have implications for how this
family of proteins is specializing to exploit hosts with varying levels of
anti-malaria immunity. The malaria parasite Plasmodium falciparum persists in the human
host partly by avoiding elimination in the spleen during blood stage infection.
This strategy depends principally upon members of the large and diverse PfEMP1
family of proteins that are exported to the surface of infected erythrocytes.
PfEMP1 proteins are important targets for host protective antibody responses and
encode binding to several different host receptor proteins. Switches in PfEMP1
expression allow parasites to evade host antibodies and may precipitate severe
disease when infected erythrocytes accumulate in brain or placenta.
Consequently, the severity of malaria infection may depend on the type of PfEMP1
protein expressed. In this study, we employ a representative panel of distinct
PfEMP1 types and host receptor proteins to demonstrate that CD36 and ICAM-1
binding properties of full-length PfEMP1 are highly predicted by their domain
composition. We also find that CD36 binding is under strong selection in many
PfEMP1 proteins, but that a group of PfEMP1s associated with more severe
infections does not bind CD36 and may utilize alternative means to sequester
infected erythrocytes. These findings have implications for understanding the
molecular basis for severe malaria.
Collapse
Affiliation(s)
- Joel H. Janes
- Department of Global Health, University of Washington, Seattle,
Washington, United States of America
| | - Christopher P. Wang
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
| | - Emily Levin-Edens
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
| | - Inès Vigan-Womas
- Institut Pasteur, Unité d'Immunologie Moléculaire des
Parasites, Paris, France
| | - Micheline Guillotte
- Institut Pasteur, Unité d'Immunologie Moléculaire des
Parasites, Paris, France
| | - Martin Melcher
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
| | - Odile Mercereau-Puijalon
- Institut Pasteur, Unité d'Immunologie Moléculaire des
Parasites, Paris, France
- CNRS URA 2581, Paris, France
| | - Joseph D. Smith
- Department of Global Health, University of Washington, Seattle,
Washington, United States of America
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
- * E-mail:
| |
Collapse
|
5
|
Melcher M, Muhle RA, Henrich PP, Kraemer SM, Avril M, Vigan-Womas I, Mercereau-Puijalon O, Smith JD, Fidock DA. Identification of a role for the PfEMP1 semi-conserved head structure in protein trafficking to the surface of Plasmodium falciparum infected red blood cells. Cell Microbiol 2010; 12:1446-62. [PMID: 20438573 DOI: 10.1111/j.1462-5822.2010.01481.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transport of Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) variants to the red blood cell (RBC) surface enables malarial parasite evasion of host immunity by modifying the antigenic and adhesive properties of infected RBCs. In this study, we applied the Bxb1 integrase system to integrate transgenes encoding truncated PfEMP1-GFP fusions into cytoadherent A4 parasites and characterize their surface transport requirements. Our studies revealed that the semi-conserved head structure of PfEMP1 proteins, in combination with the predicted transmembrane region and cytoplasmic tail, encodes sufficient information for RBC surface display. In contrast, miniPfEMP1 proteins with truncated head structures were exported to the RBC cytoplasm but were not detected at the RBC surface by flow cytometry or immuno-electron microscopy. We demonstrated the absence of a mechanistic barrier to having native and miniPfEMP1 proteins displayed simultaneously at the RBC surface. However, surface-exposed miniPfEMP1 proteins did not convey cytoadherence properties to their host cells, implicating potential steric considerations in host-receptor interactions or the need for multiple domains to mediate cell binding. This study establishes a new system to investigate PfEMP1 transport and demonstrates that the PfEMP1 semi-conserved head structure is under selection for protein transport, in addition to its known roles in adhesion.
Collapse
Affiliation(s)
- Martin Melcher
- Seattle Biomedical Research Institute, Seattle, WA, 98109, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Melcher M, Unger B, Schmidt U, Rajantie IA, Alitalo K, Ellmeier W. Essential roles for the Tec family kinases Tec and Btk in M-CSF receptor signaling pathways that regulate macrophage survival. J Immunol 2008; 180:8048-56. [PMID: 18523268 DOI: 10.4049/jimmunol.180.12.8048] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Tec family kinases have important roles in lymphocytes; however, little is known about their function in monocytes/macrophages. In this study we report that Tec family kinases are essential for M-CSF (M-CSF)-induced signaling pathways that regulate macrophage survival. Compared with wild-type bone marrow-derived macrophage (BMM) cultures, Tec(-/-)Btk(-/-) BMM cultures displayed increased cell death that correlated with a severe drop in macrophage numbers. In addition, macrophages deficient in either Tec or Btk showed expression and activation of caspase-11. Elucidation of M-CSF receptor (M-CSFR) signaling pathways revealed that the total tyrosine phosphorylation pattern upon M-CSF stimulation was altered in Tec(-/-)Btk(-/-) macrophages despite normal expression and phosphorylation of the M-CSFR. Further, Tec and Btk are required for proper expression of the GM-CSF receptor alpha (GM-CSFRalpha) chain in macrophages but not dendritic cells, implicating Tec family kinases in the lineage-specific regulation of GM-CSFRalpha expression. Taken together, our study shows that Tec and Btk regulate M-CSFR signaling-induced macrophage survival and provides a novel link between Tec family kinases and the regulation of caspase-11 and GM-CSFRalpha expression.
Collapse
Affiliation(s)
- Martin Melcher
- Institute of Immunology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, Vienna, Austria
| | | | | | | | | | | |
Collapse
|
7
|
Melcher M, Schreiner M. Statistical evaluation of potash-lime-silica glass weathering. Anal Bioanal Chem 2004; 379:628-39. [PMID: 15067493 DOI: 10.1007/s00216-004-2595-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 02/26/2004] [Accepted: 03/08/2004] [Indexed: 10/26/2022]
Abstract
Two potash-lime-silica model glasses with compositions similar to those of medieval stained glass were exposed at 26 test sites all over Europe and in North America for 3-6 years. The objectives of this large-scale field exposure programme were: (a) a qualitative analysis of the weathering products formed on the surface of the samples in the (environmental) scanning electron microscope in combination with energy dispersive X-ray microanalysis (ESEM/EDX or SEM/EDX, respectively); (b) a statistical evaluation of the weathering phenomena by applying a multiple linear regression (MLR) analysis to find correlations between the degree of weathering, which was measured in terms of surface coverage with reaction products, and environmental parameters such as the concentration (c) of the acidifying gases SO(2), NO(2) and O(3), the temperature (T) and the relative humidity (RH); and (c) the calculation of a time-dependence function of the weathering process of these glasses. Mainly sulfates of calcium and potassium such as gypsum (CaSO(4).2 H(2)O), arcanite (K(2)SO(4)) and syngenite (CaSO(4).K(2)SO(4).H(2)O) could be identified in the SEM and ESEM. Carbonates, nitrates and many particles deposited on the glass surface were found as well. MLR calculations exhibit significant dependencies of the degree of weathering on T, RH, c(NO(x)), c(SO(2)) and c(O(3)). Applying a time-dependence function of the general form y= a. t(b) (t=time) results in a value of approximately 0.42 for the exponent b, which comes close to values expected from various studies in the literature.
Collapse
Affiliation(s)
- M Melcher
- Institute of Science and Technology in Art, Academy of Fine Arts, Schillerplatz 3, 1010 Vienna, Austria.
| | | |
Collapse
|
8
|
Sewalt RGAB, Lachner M, Vargas M, Hamer KM, den Blaauwen JL, Hendrix T, Melcher M, Schweizer D, Jenuwein T, Otte AP. Selective interactions between vertebrate polycomb homologs and the SUV39H1 histone lysine methyltransferase suggest that histone H3-K9 methylation contributes to chromosomal targeting of Polycomb group proteins. Mol Cell Biol 2002; 22:5539-53. [PMID: 12101246 PMCID: PMC133945 DOI: 10.1128/mcb.22.15.5539-5553.2002] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Polycomb group (PcG) proteins form multimeric chromatin-associated protein complexes that are involved in heritable repression of gene activity. Two distinct human PcG complexes have been characterized. The EED/EZH2 PcG complex utilizes histone deacetylation to repress gene activity. The HPC/HPH PcG complex contains the HPH, RING1, BMI1, and HPC proteins. Here we show that vertebrate Polycomb homologs HPC2 and XPc2, but not M33/MPc1, interact with the histone lysine methyltransferase (HMTase) SUV39H1 both in vitro and in vivo. We further find that overexpression of SUV39H1 induces selective nuclear relocalization of HPC/HPH PcG proteins but not of the EED/EZH2 PcG proteins. This SUV39H1-dependent relocalization concentrates the HPC/HPH PcG proteins to the large pericentromeric heterochromatin domains (1q12) on human chromosome 1. Within these PcG domains we observe increased H3-K9 methylation. Finally, we show that H3-K9 HMTase activity is associated with endogenous HPC2. Our findings suggest a role for the SUV39H1 HMTase and histone H3-K9 methylation in the targeting of human HPC/HPH PcG proteins to modified chromatin structures.
Collapse
Affiliation(s)
- Richard G A B Sewalt
- Swammerdam Institute for Life Sciences, BioCentrum Amsterdam, University of Amsterdam, Plantage Muidergracht 12, 1018 TV Amsterdam, The Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Pasierbek P, Jantsch M, Melcher M, Schleiffer A, Schweizer D, Loidl J. A Caenorhabditis elegans cohesion protein with functions in meiotic chromosome pairing and disjunction. Genes Dev 2001; 15:1349-60. [PMID: 11390355 PMCID: PMC312707 DOI: 10.1101/gad.192701] [Citation(s) in RCA: 275] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We have studied four Caenorhabditis elegans homologs of the Rad21/Scc1/Rec8 sister-chromatid cohesion protein family. Based on the RNAi phenotype and protein localization, it is concluded that one of them, W02A2.6p, is the likely worm ortholog of yeast Rec8p. The depletion of C. elegans W02A2.6p (called REC-8) by RNAi, induced univalent formation and splitting of chromosomes into sister chromatids at diakinesis. Chromosome synapsis at pachytene was defective, but primary homology recognition seemed unaffected, as a closer-than-random association of homologous fluorescence in situ hybridization (FISH) signals at leptotene/zygotene was observed. Depletion of REC-8 also induced chromosome fragmentation at diakinesis. We interpret these fragments as products of unrepaired meiotic double-stranded DNA breaks (DSBs), because fragmentation was suppressed in a spo-11 background. Thus, REC-8 seems to be required for successful repair of DSBs. The occurrence of DSBs in REC-8-depleted meiocytes suggests that DSB formation does not depend on homologous synapsis. Anti-REC-8 immunostaining decorated synaptonemal complexes (SCs) at pachytene and chromosomal axes in bivalents and univalents at diakinesis. Between metaphase I and metaphase II, REC-8 is partially lost from the chromosomes. The partial loss of REC-8 from chromosomes between metaphase I and metaphase II suggests that worm REC-8 might function similarly to yeast Rec8p. The loss of yeast Rec8p from chromosome arms at meiosis I and centromeres at meiosis II coordinates the disjunction of homologs and sister chromatids at the two meiotic divisions.
Collapse
Affiliation(s)
- P Pasierbek
- Department of Cytology and Genetics, Institute of Botany, University of Vienna, A-1030 Vienna, Austria
| | | | | | | | | | | |
Collapse
|
10
|
Melcher M, Schmid M, Aagaard L, Selenko P, Laible G, Jenuwein T. Structure-function analysis of SUV39H1 reveals a dominant role in heterochromatin organization, chromosome segregation, and mitotic progression. Mol Cell Biol 2000; 20:3728-41. [PMID: 10779362 PMCID: PMC85674 DOI: 10.1128/mcb.20.10.3728-3741.2000] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
SUV39H1, a human homologue of the Drosophila position effect variegation modifier Su(var)3-9 and of the Schizosaccharomyces pombe silencing factor clr4, encodes a novel heterochromatic protein that transiently accumulates at centromeric positions during mitosis. Using a detailed structure-function analysis of SUV39H1 mutant proteins in transfected cells, we now show that deregulated SUV39H1 interferes at multiple levels with mammalian higher-order chromatin organization. First, forced expression of full-length SUV39H1 (412 amino acids) redistributes endogenous M31 (HP1beta) and induces abundant associations with inter- and metaphase chromatin. These properties depend on the C-terminal SET domain, although the major portion of the SUV39H1 protein (amino acids 89 to 412) does not display affinity for nuclear chromatin. By contrast, the M31 interaction surface, which was mapped to the first 44 N-terminal amino acids, together with the immediately adjacent chromo domain, directs specific accumulation at heterochromatin. Second, cells overexpressing full-length SUV39H1 display severe defects in mitotic progression and chromosome segregation. Surprisingly, whereas localization of centromere proteins is unaltered, the focal, G(2)-specific distribution of phosphorylated histone H3 at serine 10 (phosH3) is dispersed in these cells. This phosH3 shift is not observed with C-terminally truncated mutant SUV39H1 proteins or with deregulated M31. Together, our data reveal a dominant role(s) for the SET domain of SUV39H1 in the distribution of prominent heterochromatic proteins and suggest a possible link between a chromosomal SU(VAR) protein and histone H3.
Collapse
Affiliation(s)
- M Melcher
- Research Institute of Molecular Pathology, The Vienna Biocenter, A-1030 Vienna, Austria
| | | | | | | | | | | |
Collapse
|
11
|
Welz B, Melcher M. Decomposition of marine biological tissues for determination of arsenic, selenium, and mercury using hydride-generation and cold-vapor atomic absorption spectrometries. Anal Chem 1985; 57:427-31. [PMID: 3977073 DOI: 10.1021/ac50001a024] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
12
|
|
13
|
Abstract
A rare mixed malignant hepatic tumor in a 35-year-old woman is presented. Hepatic enlargement regressed and became stable for 3 years after contraceptive pills were discontinued. Exacerbation began 3 months prior to admission, at which time there was a spontaneous rupture of the tumor; this resulted in the death of the patient.
Collapse
|
14
|
|