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Genomic Localization of TgSMC1 in Toxoplasma gondii parasites

ABSTRACT: Apicomplexa are intracellular parasites that cause human and animal disease. They proliferate by a unique mechanism that combines closed mitosis with daughter cell budding. In past work we demonstrated that the Toxoplasma gondii centromeres are sequestered to the nuclear periphery proximal to the centrosome throughout the cell cycle. Here we show that interphase centromere clustering is not mediated by the mitotic spindle. Instead we propose a chromatin model of centromere clustering and define structural maintenance of chromosomes protein 1 (SMC1) as a persisting centromeric protein. We biochemically identify proteins that physically interact with SMC1, and CenH3 (a centromeric histone); prominent among those are predicted peripheral soluble components of the nuclear pore complex including TgExportin1. Treatment of parasites with the highly specific exportin1 inhibitor leptomycin B causes the dispersal of centromeres. Our results suggest that the nuclear envelope, and in particular peripheral components of the nuclear transport machinery orchestrate centromere positioning and parasite nuclear architecture. Chromatin immunoprecipitation (ChIP) of TgSMC1, three replicates applied to two microarrays each representing half of the Toxoplasma genome

ORGANISM(S): Toxoplasma gondii

SUBMITTER: Kami Kim

PROVIDER: E-GEOD-61806 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Genomic Localization of TgSMC1 in Toxoplasma gondii parasites

Project description:Apicomplexa are intracellular parasites that cause human and animal disease. They proliferate by a unique mechanism that combines closed mitosis with daughter cell budding. In past work we demonstrated that the Toxoplasma gondii centromeres are sequestered to the nuclear periphery proximal to the centrosome throughout the cell cycle. Here we show that interphase centromere clustering is not mediated by the mitotic spindle. Instead we propose a chromatin model of centromere clustering and define structural maintenance of chromosomes protein 1 (SMC1) as a persisting centromeric protein. We biochemically identify proteins that physically interact with SMC1, and CenH3 (a centromeric histone); prominent among those are predicted peripheral soluble components of the nuclear pore complex including TgExportin1. Treatment of parasites with the highly specific exportin1 inhibitor leptomycin B causes the dispersal of centromeres. Our results suggest that the nuclear envelope, and in particular peripheral components of the nuclear transport machinery orchestrate centromere positioning and parasite nuclear architecture.

2014-09-27 | GSE61806 | GEO

Direct recruitment of Mis18 to interphase spindle poles promotes CENP-A chromatin assembly.

Project description:CENP-A chromatin specifies mammalian centromere identity, and its chaperone HJURP replenishes CENP-A when recruited by the Mis18 complex (Mis18C) via M18BP/KNL2 to CENP-C at kinetochores during interphase. However, the Mis18C recruitment mechanism remains unresolved in species lacking M18BP1, such as fission yeast. Fission yeast centromeres cluster at G2 spindle pole bodies (SPBs) when CENP-ACnp1 is replenished and where Mis18C also localizes. We show that SPBs play an unexpected role in concentrating Mis18C near centromeres through the recruitment of Mis18 by direct binding to the major SPB LInker of Nucleoskeleton and Cytoskeleton (LINC) complex component Sad1. Mis18 recruitment by Sad1 is important for CENP-ACnp1 chromatin establishment and acts in parallel with a CENP-C-mediated Mis18C recruitment pathway to maintain centromeric CENP-ACnp1, but is independent of Sad1-mediated centromere clustering. SPBs therefore provide a non-chromosomal scaffold for both Mis18C recruitment and centromere clustering during G2. This centromere-independent Mis18-SPB recruitment provides a mechanism that governs de novo CENP-ACnp1 chromatin assembly by the proximity of appropriate sequences to SPBs and highlights how nuclear spatial organization influences centromere identity.

2023-09-18 | PXD045191 | Pride

SUMOylation regulates Lem2 function in centromere clustering and silencing.

Project description:Regulation by the small modifier SUMO is heavily dependent on spatial control of enzymes that mediate the attachment and removal of SUMO on substrate proteins. Here we show that in fission yeast, delocalisation of the SUMO protease Ulp1 from the nuclear envelope results in centromeric defects that can be attributed to hyper-SUMOylation at the nuclear periphery. Unexpectedly, we find that while this localised hyper-SUMOylation impairs centromeric silencing, it can also enhance centromere clustering. Moreover, both effects are at least partially dependent on SUMOylation of the inner nuclear membrane protein Lem2. Lem2 has previously been implicated in diverse biological processes, including the promotion of both centromere clustering and silencing, but how these distinct activities are coordinated was unclear; our observations suggest a model whereby SUMOylation may serve as a regulatory switch, modulating Lem2 interactions with competing partner proteins to balance its roles in alternative pathways. Our findings also reveal a previously unappreciated role for SUMOylation in promoting centromere clustering.

2023-11-20 | PXD046003 | Pride

Centromere-Like Regions in Budding Yeast

Project description:Accurate chromosome segregation requires centromeres (CENs), the chromosomal sites where kinetochores form, to bridge DNA and attach to microtubules. In contrast to most eukaryotes, Saccharomyces cerevisiae possesses sequence-defined point centromeres. Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) of four kinetochore components reveals regions of overlapping, extra-centromeric protein localization upon overproduction of the centromeric histone, Cse4 (CENP-A or CenH3). These identified sequences enhance proper plasmid and chromosome segregation, and are termed Centromere-like Regions (CLRs). CLRs form in close proximity to S. cerevisiae CENs and share characteristics typical of point and regional centromeres. CLR sequences are conserved among related budding yeasts, suggesting a role in vivo. These studies provide new insights into the origin and evolution of centromeres. ChIP-Seq analysis of the kinetochore components Cse4, Mif2, Ndc10 and Ndc80 in budding yeast strains (Saccharomyces cerevisiae) with normal and elevated levels of Cse4

2013-01-18 | E-GEOD-31466 | biostudies-arrayexpress

LC-MS/MS analysis of immunoprecipitation samples of Tetrahymena meiotic proteins Melg1, Melg2, Melg3, and Tass1

Project description:In most eukaryotes, the meiotic chromosomal bouquet (comprising clustered chromosome ends) provides an ordered chromosome arrangement that facilitates pairing and recombination between homologous chromosomes. In the protist Tetrahymena thermophila, the meiotic prophase nucleus stretches enormously and chromosomes assume a bouquet-like arrangement in which telomeres and centromeres are attached to opposite poles of the nucleus. We have identified and characterized three meiosis-specific genes (MELG1-3) that control nuclear elongation and centromere and telomere clustering. Hence, to find out potential interactions, we did LC-MS/MS analysis for Melg1, Melg2, Melg3, and Tass1 (a partner of Melg3) immunoprecipitation samples.

2020-11-23 | PXD021813 | Pride

Identification and characterization of centromeric sequences in Xenopus laevis

Project description:Centromeres play an essential role in cell division by specifying the site of kinetochore formation on each chromosome so that chromosomes can attach to the mitotic spindle for segregation. Centromeres are defined epigenetically by the histone H3 variant CEntromere Protein A (CENP-A). Dividing cells maintain the centromere by depositing new CENP-A each cell cycle to replenish CENP-A diluted by replication. The CENP-A nucleosome serves as the primary signal to the machinery responsible for its replenishment. Vertebrate centromeres are frequently built on repetitive sequences organized in tandem arrays. Repetitive centromeric DNA has been suggested to play a role in centromere maintenance and in de novo centromere formation, but this has been difficult to dissect because of the difficulty in manipulating centromere in cells. Extracts from Xenopus laevis eggs are able to assemble centromeres and kinetochores in vitro and thus provide a useful system for studying the role of centromeric DNA in centromere formation. However centromeric sequences in X. laevis have not been extensively characterized.. In this study we characterize repeat sequences found at X. laevis centromeres. We utilize a k-mer based approach in order to uncover the previously unknown diversity of X. laevis centromeric sequences. We validate centromere localization of repeat sequences by in situ hybridization and identify the location of the centromeric repetitive array on each chromosome by mapping the distribution of centromere enriched k-mers on the Xenopus genome. Our identification of X. laevis centromere sequences enables previously unapproachable genomic studies of centromeres. The k-mer based approach that we used to investigate centromeric repetitive DNA is suitable for the analysis of other repetitive sequences found across the genome or the study of repeats in other organisms.

2020-06-24 | GSE153058 | GEO

Centromeric H2B monoubiquitination promotes noncoding transcription and chromatin integrity

Project description:Functional centromeres are essential for proper cell division. Centromeres are established largely by epigenetic processes resulting in incorporation of the histone H3 variant CENP-A. Here, we demonstrate the direct involvement of H2B monoubiquitination, mediated by RNF20 in humans or Brl1 in Schizosaccharomyces pombe, in centromeric chromatin maintenance. Monoubiquinated H2B (H2Bub1) is needed for this maintenance, promoting noncoding transcription, centromere integrity and accurate chromosomal segregation. A transient pulse of centromeric H2Bub1 leads to RNA polymerase II–mediated transcription of the centromere’s central domain, coupled to decreased H3 stability. H2Bub1-deficient cells have centromere cores that, despite their intact centromeric heterochromatin barriers, exhibit characteristics of heterochromatin, such as silencing histone modifications, reduced nucleosome turnover and reduced levels of transcription. In the H2Bub1-deficient cells, centromere functionality is hampered, thus resulting in unequal chromosome segregation. Therefore, centromeric H2Bub1 is essential for maintaining active centromeric chromatin.

2014-01-29 | GSE49874 | GEO

Ccp1 homodimer mediates chromatin integrity by antagonizing CENP-A loading

Project description:CENP-A is a centromere-specific histone 3 variant essential for centromere specification. CENP-A partially replaces canonical histone H3 at the centromeres. How the particular CENP-A/H3 ratio at centromeres is precisely maintained is unknown. It also remains unclear how CENP-A is excluded from non-centromeric chromatin. Here we identify Ccp1, an uncharacterized NAP family protein in fission yeast that antagonizes CENP-A loading at both centromeric and non-centromeric regions. Like the CENP-A loading factor HJURP, Ccp1 interacts with CENP-A, and is recruited to centromeres at the end of mitosis in a Mis16-dependent manner. These data indicate that factors with opposing CENP-A loading activities are recruited to centromeres. Furthermore, Ccp1 also cooperates with H2A.Z to evict CENP-A assembled in euchromatin. Structural analyses indicate that Ccp1 forms a homodimer that is required for its anti-CENP-A loading activity. Our study establishes mechanisms for maintenance of CENP-A homeostasis at centromeres and the prevention of ectopic assembly of centromeres. Examination of cnp1 distribution in one wild type (wt) and two ccp1 mutants.

2016-08-04 | E-GEOD-85166 | biostudies-arrayexpress

Ccp1 homodimer mediates chromatin integrity by antagonizing CENP-A loading

2016-08-04 | GSE85166 | GEO

CENP-A associated lncRNAs influence chromosome segregation in human cells

Project description:Transcription occurs ubiquitously throughout non-coding parts of the genome, including at repetitive alpha-satellite DNA elements which comprise the majority of human centromeres. The function of temporally regulated centromeric transcription, and transcripts, is consequently a topic of intense investigation. In this study, we use high throughput approaches to identify and describe lncRNAs associated with the centromere specific histone variant CENP-A that arise from the transcription of specific centromeres at early G1, which we then show are physically associated with centromeres, and which are functionally necessary for accurate chromosome segregation. Targeted depletion of one such centromeric RNA, which originates from a single centromere, is sufficient to increase the frequency of chromosome segregation defects. These data support the emerging paradigm of the necessity of centromere-specific lncRNAs in the integrity of faithful chromosome segregation.

2019-11-26 | GSE137377 | GEO

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