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Sullivan LL, Maloney KA, Towers AJ, Gregory SG, Sullivan BA. Human centromere repositioning within euchromatin after partial chromosome deletion. Chromosome Res 2016; 24:451-466. [PMID: 27581771 DOI: 10.1007/s10577-016-9536-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 08/18/2016] [Accepted: 08/22/2016] [Indexed: 10/21/2022]
Abstract
Centromeres are defined by a specialized chromatin organization that includes nucleosomes that contain the centromeric histone variant centromere protein A (CENP-A) instead of canonical histone H3. Studies in various organisms have shown that centromeric chromatin (i.e., CENP-A chromatin or centrochromatin) exhibits plasticity, in that it can assemble on different types of DNA sequences. However, once established on a chromosome, the centromere is maintained at the same position. In humans, this location is the highly homogeneous repetitive DNA alpha satellite. Mislocalization of centromeric chromatin to atypical locations can lead to genome instability, indicating that restriction of centromeres to a distinct genomic position is important for cell and organism viability. Here, we describe a rearrangement of Homo sapiens chromosome 17 (HSA17) that has placed alpha satellite DNA next to euchromatin. We show that on this mutant chromosome, CENP-A chromatin has spread from the alpha satellite into the short arm of HSA17, establishing a ∼700 kb hybrid centromeric domain that spans both repetitive and unique sequences and changes the expression of at least one gene over which it spreads. Our results illustrate the plasticity of human centromeric chromatin and suggest that heterochromatin normally constrains CENP-A chromatin onto alpha satellite DNA. This work highlights that chromosome rearrangements, particularly those that remove the pericentromere, create opportunities for centromeric nucleosomes to move into non-traditional genomic locations, potentially changing the surrounding chromatin environment and altering gene expression.
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Affiliation(s)
- Lori L Sullivan
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3054, Durham, NC, 27710, USA
| | - Kristin A Maloney
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3054, Durham, NC, 27710, USA.,Department of Medicine, Division of Endocrinology, Diabetes, and Nutrition, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Aaron J Towers
- University Program in Genetics and Genomics, Duke University School of Medicine, Durham, NC, 27710, USA.,Quintiles, 4820 Emperor Blvd., Durham, NC, 27703, USA
| | - Simon G Gregory
- Department of Medicine, Duke Molecular Physiology Institute, 300 N. Duke Street, Durham, NC, 27701, USA.,Division of Human Genetics, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Beth A Sullivan
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3054, Durham, NC, 27710, USA. .,Quintiles, 4820 Emperor Blvd., Durham, NC, 27703, USA.
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Zhang L, Zhou Z, Guo Q, Fokkens L, Miskei M, Pócsi I, Zhang W, Chen M, Wang L, Sun Y, Donzelli BGG, Gibson DM, Nelson DR, Luo JG, Rep M, Liu H, Yang S, Wang J, Krasnoff SB, Xu Y, Molnár I, Lin M. Insights into Adaptations to a Near-Obligate Nematode Endoparasitic Lifestyle from the Finished Genome of Drechmeria coniospora. Sci Rep 2016; 6:23122. [PMID: 26975455 PMCID: PMC4792172 DOI: 10.1038/srep23122] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/29/2016] [Indexed: 12/18/2022] Open
Abstract
Nematophagous fungi employ three distinct predatory strategies: nematode trapping, parasitism of females and eggs, and endoparasitism. While endoparasites play key roles in controlling nematode populations in nature, their application for integrated pest management is hindered by the limited understanding of their biology. We present a comparative analysis of a high quality finished genome assembly of Drechmeria coniospora, a model endoparasitic nematophagous fungus, integrated with a transcriptomic study. Adaptation of D. coniospora to its almost completely obligate endoparasitic lifestyle led to the simplification of many orthologous gene families involved in the saprophytic trophic mode, while maintaining orthologs of most known fungal pathogen-host interaction proteins, stress response circuits and putative effectors of the small secreted protein type. The need to adhere to and penetrate the host cuticle led to a selective radiation of surface proteins and hydrolytic enzymes. Although the endoparasite has a simplified secondary metabolome, it produces a novel peptaibiotic family that shows antibacterial, antifungal and nematicidal activities. Our analyses emphasize the basic malleability of the D. coniospora genome: loss of genes advantageous for the saprophytic lifestyle; modulation of elements that its cohort species utilize for entomopathogenesis; and expansion of protein families necessary for the nematode endoparasitic lifestyle.
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Affiliation(s)
- Liwen Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Zhengfu Zhou
- Key Laboratory of Agricultural Genomics (Beijing), Ministry of Agriculture, China
| | - Qiannan Guo
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Like Fokkens
- Molecular Plant Pathology, University of Amsterdam, Amsterdam, the Netherlands
| | - Márton Miskei
- Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Hungary
- Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen, Hungary
| | - István Pócsi
- Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Hungary
| | - Wei Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Ming Chen
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Lei Wang
- Tianjin Key Laboratory of Microbial Functional Genomics, TEDA School of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Yamin Sun
- Tianjin Key Laboratory of Microbial Functional Genomics, TEDA School of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Bruno G. G. Donzelli
- Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, New York, USA
| | - Donna M. Gibson
- USDA-ARS, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, USA
| | - David R. Nelson
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Jian-Guang Luo
- State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, China
| | - Martijn Rep
- Molecular Plant Pathology, University of Amsterdam, Amsterdam, the Netherlands
| | - Hang Liu
- Key Laboratory of Agricultural Genomics (Beijing), Ministry of Agriculture, China
| | - Shengnan Yang
- Key Laboratory of Agricultural Genomics (Beijing), Ministry of Agriculture, China
| | - Jing Wang
- Key Laboratory of Agricultural Genomics (Beijing), Ministry of Agriculture, China
| | - Stuart B. Krasnoff
- USDA-ARS, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, USA
| | - Yuquan Xu
- Key Laboratory of Agricultural Genomics (Beijing), Ministry of Agriculture, China
| | - István Molnár
- Natural Products Center, School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, USA
| | - Min Lin
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
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Ohkuni K, Takahashi Y, Fulp A, Lawrimore J, Au WC, Pasupala N, Levy-Myers R, Warren J, Strunnikov A, Baker RE, Kerscher O, Bloom K, Basrai MA. SUMO-Targeted Ubiquitin Ligase (STUbL) Slx5 regulates proteolysis of centromeric histone H3 variant Cse4 and prevents its mislocalization to euchromatin. Mol Biol Cell 2016; 27:mbc.E15-12-0827. [PMID: 26960795 PMCID: PMC4850037 DOI: 10.1091/mbc.e15-12-0827] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 02/17/2016] [Accepted: 03/03/2016] [Indexed: 12/14/2022] Open
Abstract
Centromeric histone H3, CENP-ACse4, is essential for faithful chromosome segregation. Stringent regulation of cellular levels of CENP-ACse4 restricts its localization to centromeres. Mislocalization of CENP-ACse4 is associated with aneuploidy in yeast, flies and tumorigenesis in human cells; thus, defining pathways that regulate CENP-A levels is critical for understanding how mislocalization of CENP-A contributes to aneuploidy in human cancers. Previous work in budding yeast has shown that ubiquitination of overexpressed Cse4 by Psh1, an E3 ligase, partially contributes to proteolysis of Cse4. Here, we provide the first evidence that Cse4 is sumoylated by E3 ligases Siz1 and Siz2 in vivo and in vitro. Ubiquitination of Cse4 by Small Ubiquitin-related Modifier (SUMO)-Targeted Ubiquitin Ligase (STUbL) Slx5 plays a critical role in proteolysis of Cse4 and prevents mislocalization of Cse4 to euchromatin under normal physiological conditions. Accumulation of sumoylated Cse4 species and increased stability of Cse4 in slx5∆ strains suggest that sumoylation precedes ubiquitin-mediated proteolysis of Cse4. Slx5-mediated Cse4 proteolysis is independent of Psh1 since slx5∆ psh1∆ strains exhibit higher levels of Cse4 stability and mislocalization compared to either slx5∆ or psh1∆ strains. Our results demonstrate a role for Slx5 in ubiquitin-mediated proteolysis of Cse4 to prevent its mislocalization and maintain genome stability.
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Affiliation(s)
- Kentaro Ohkuni
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Yoshimitsu Takahashi
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Alyona Fulp
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Josh Lawrimore
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Wei-Chun Au
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Nagesh Pasupala
- Biology Department, The College of William & Mary, Williamsburg, VA 23187
| | - Reuben Levy-Myers
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
- Biology Department, The College of William & Mary, Williamsburg, VA 23187
| | - Jack Warren
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | | | - Richard E. Baker
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01655
| | - Oliver Kerscher
- Biology Department, The College of William & Mary, Williamsburg, VA 23187
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Munira A. Basrai
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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Freitag M. The kinetochore interaction network (KIN) of ascomycetes. Mycologia 2016; 108:485-505. [PMID: 26908646 DOI: 10.3852/15-182] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 10/23/2015] [Indexed: 01/13/2023]
Abstract
Chromosome segregation relies on coordinated activity of a large assembly of proteins, the kinetochore interaction network (KIN). How conserved the underlying mechanisms driving the epigenetic phenomenon of centromere and kinetochore assembly and maintenance are remains unclear, even though various eukaryotic models have been studied. More than 50 different proteins, many in multiple copies, comprise the KIN or are associated with fungal centromeres and kinetochores. Proteins isolated from immune sera recognized centromeric regions on chromosomes and thus were named centromere proteins (CENPs). CENP-A, sometimes called centromere-specific H3 (CenH3), is incorporated into nucleosomes within or near centromeres. The constitutive centromere-associated network (CCAN) assembles on this specialized chromatin, likely based on specific interactions with and requiring presence of CENP-C. The outer kinetochore comprises the Knl1-Mis12-Ndc80 (KMN) protein complexes that connect CCAN to spindles, accomplished by binding and stabilizing microtubules (MTs) and in the process generating load-bearing assemblies for chromatid segregation. In most fungi the Dam1/DASH complex connects the KMN complexes to MTs. Fungi present a rich resource to investigate mechanistic commonalities but also differences in kinetochore architecture. While ascomycetes have sets of CCAN and KMN proteins that are conserved with those of budding yeast or metazoans, searching other major branches of the fungal kingdom revealed that CCAN proteins are poorly conserved at the primary sequence level. Several conserved binding motifs or domains within KMN complexes have been described recently, and these features of ascomycete KIN proteins are shared with most metazoan proteins. In addition, several ascomycete-specific domains have been identified here.
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Affiliation(s)
- Michael Freitag
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305
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55
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Abstract
Production of gametes of halved ploidy for sexual reproduction requires a specialized cell division called meiosis. The fusion of two gametes restores the original ploidy in the new generation, and meiosis thus stabilizes ploidy across generations. To ensure balanced distribution of chromosomes, pairs of homologous chromosomes (homologs) must recognize each other and pair in the first meiotic division. Recombination plays a key role in this in most studied species, but it is not the only actor and particular chromosomal regions are known to facilitate the meiotic pairing of homologs. In this review, we focus on the roles of centromeres and in particular on the clustering and pairwise associations of nonhomologous centromeres that precede stable pairing between homologs. Although details vary from species to species, it is becoming increasingly clear that these associations play active roles in the meiotic chromosome pairing process, analogous to those of the telomere bouquet.
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Affiliation(s)
- Olivier Da Ines
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France; ,
| | - Charles I White
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France; ,
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Koo DH, Sehgal SK, Friebe B, Gill BS. Structure and Stability of Telocentric Chromosomes in Wheat. PLoS One 2015; 10:e0137747. [PMID: 26381743 PMCID: PMC4575054 DOI: 10.1371/journal.pone.0137747] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 08/21/2015] [Indexed: 01/04/2023] Open
Abstract
In most eukaryotes, centromeres assemble at a single location per chromosome. Naturally occurring telocentric chromosomes (telosomes) with a terminal centromere are rare but do exist. Telosomes arise through misdivision of centromeres in normal chromosomes, and their cytological stability depends on the structure of their kinetochores. The instability of telosomes may be attributed to the relative centromere size and the degree of completeness of their kinetochore. Here we test this hypothesis by analyzing the cytogenetic structure of wheat telosomes. We used a population of 80 telosomes arising from the misdivision of the 21 chromosomes of wheat that have shown stable inheritance over many generations. We analyzed centromere size by probing with the centromere-specific histone H3 variant, CENH3. Comparing the signal intensity for CENH3 between the intact chromosome and derived telosomes showed that the telosomes had approximately half the signal intensity compared to that of normal chromosomes. Immunofluorescence of CENH3 in a wheat stock with 28 telosomes revealed that none of the telosomes received a complete CENH3 domain. Some of the telosomes lacked centromere specific retrotransposons of wheat in the CENH3 domain, indicating that the stability of telosomes depends on the presence of CENH3 chromatin and not on the presence of CRW repeats. In addition to providing evidence for centromere shift, we also observed chromosomal aberrations including inversions and deletions in the short arm telosomes of double ditelosomic 1D and 6D stocks. The role of centromere-flanking, pericentromeric heterochromatin in mitosis is discussed with respect to genome/chromosome integrity.
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Affiliation(s)
- Dal-Hoe Koo
- Department of Plant Pathology, Wheat Genetics Resource Center, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS, 66506–5502, United States of America
| | - Sunish K. Sehgal
- Department of Plant Science, South Dakota State University, Brookings, SD, 57007, United States of America
| | - Bernd Friebe
- Department of Plant Pathology, Wheat Genetics Resource Center, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS, 66506–5502, United States of America
- * E-mail:
| | - Bikram S. Gill
- Department of Plant Pathology, Wheat Genetics Resource Center, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS, 66506–5502, United States of America
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Dobigny G, Britton-Davidian J, Robinson TJ. Chromosomal polymorphism in mammals: an evolutionary perspective. Biol Rev Camb Philos Soc 2015; 92:1-21. [PMID: 26234165 DOI: 10.1111/brv.12213] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 06/23/2015] [Accepted: 07/09/2015] [Indexed: 12/28/2022]
Abstract
Although chromosome rearrangements (CRs) are central to studies of genome evolution, our understanding of the evolutionary consequences of the early stages of karyotypic differentiation (i.e. polymorphism), especially the non-meiotic impacts, is surprisingly limited. We review the available data on chromosomal polymorphisms in mammals so as to identify taxa that hold promise for developing a more comprehensive understanding of chromosomal change. In doing so, we address several key questions: (i) to what extent are mammalian karyotypes polymorphic, and what types of rearrangements are principally involved? (ii) Are some mammalian lineages more prone to chromosomal polymorphism than others? More specifically, do (karyotypically) polymorphic mammalian species belong to lineages that are also characterized by past, extensive karyotype repatterning? (iii) How long can chromosomal polymorphisms persist in mammals? We discuss the evolutionary implications of these questions and propose several research avenues that may shed light on the role of chromosome change in the diversification of mammalian populations and species.
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Affiliation(s)
- Gauthier Dobigny
- Institut de Recherche pour le Développement, Centre de Biologie pour la Gestion des Populations (UMR IRD-INRA-Cirad-Montpellier SupAgro), Campus International de Baillarguet, CS30016, 34988, Montferrier-sur-Lez, France
| | - Janice Britton-Davidian
- Institut des Sciences de l'Evolution, Université de Montpellier, CNRS, IRD, EPHE, Cc065, Place Eugène Bataillon, 34095, Montpellier Cedex 5, France
| | - Terence J Robinson
- Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland, Stellenbosch, 7062, South Africa
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Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize. Proc Natl Acad Sci U S A 2015; 112:E1263-71. [PMID: 25733907 DOI: 10.1073/pnas.1418248112] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity.
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Cuacos M, H. Franklin FC, Heckmann S. Atypical centromeres in plants-what they can tell us. FRONTIERS IN PLANT SCIENCE 2015; 6:913. [PMID: 26579160 PMCID: PMC4620154 DOI: 10.3389/fpls.2015.00913] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 10/12/2015] [Indexed: 05/20/2023]
Abstract
The centromere, visible as the primary constriction of condensed metaphase chromosomes, is a defined chromosomal locus essential for genome stability. It mediates transient assembly of a multi-protein complex, the kinetochore, which enables interaction with spindle fibers and thus faithful segregation of the genetic information during nuclear divisions. Centromeric DNA varies in extent and sequence composition among organisms, but a common feature of almost all active eukaryotic centromeres is the presence of the centromeric histone H3 variant cenH3 (a.k.a. CENP-A). These typical centromere features apply to most studied species. However, a number of species display "atypical" centromeres, such as holocentromeres (centromere extension along almost the entire chromatid length) or neocentromeres (ectopic centromere activity). In this review, we provide an overview of different atypical centromere types found in plants including holocentromeres, de novo formed centromeres and terminal neocentromeres as well as di-, tri- and metapolycentromeres (more than one centromere per chromosomes). We discuss their specific and common features and compare them to centromere types found in other eukaryotic species. We also highlight new insights into centromere biology gained in plants with atypical centromeres such as distinct mechanisms to define a holocentromere, specific adaptations in species with holocentromeres during meiosis or various scenarios leading to neocentromere formation.
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Liu Y, Su H, Zhang J, Liu Y, Han F, Birchler JA. Dynamic epigenetic states of maize centromeres. FRONTIERS IN PLANT SCIENCE 2015; 6:904. [PMID: 26579154 PMCID: PMC4620398 DOI: 10.3389/fpls.2015.00904] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 10/10/2015] [Indexed: 05/03/2023]
Abstract
The centromere is a specialized chromosomal region identified as the major constriction, upon which the kinetochore complex is formed, ensuring accurate chromosome orientation and segregation during cell division. The rapid evolution of centromere DNA sequence and the conserved centromere function are two contradictory aspects of centromere biology. Indeed, the sole presence of genetic sequence is not sufficient for centromere formation. Various dicentric chromosomes with one inactive centromere have been recognized. It has also been found that de novo centromere formation is common on fragments in which centromeric DNA sequences are lost. Epigenetic factors play important roles in centromeric chromatin assembly and maintenance. Non-disjunction of the supernumerary B chromosome centromere is independent of centromere function, but centromere pairing during early prophase of meiosis I requires an active centromere. This review discusses recent studies in maize about genetic and epigenetic elements regulating formation and maintenance of centromere chromatin, as well as centromere behavior in meiosis.
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Affiliation(s)
- Yalin Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of SciencesBeijing, China
- University of Chinese Academy of SciencesBeijing, China
| | - Handong Su
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of SciencesBeijing, China
- University of Chinese Academy of SciencesBeijing, China
| | - Jing Zhang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of SciencesBeijing, China
| | - Yang Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of SciencesBeijing, China
- University of Chinese Academy of SciencesBeijing, China
| | - Fangpu Han
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of SciencesBeijing, China
| | - James A. Birchler
- Division of Biological Sciences, University of Missouri at Columbia, ColumbiaMO, USA
- *Correspondence: James A. Birchler,
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61
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Affiliation(s)
- J Peter Svensson
- Department of Biosciences & Nutrition, Karolinska Institutet, Huddinge, Sweden
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Macchia G, Nord KH, Zoli M, Purgato S, D'Addabbo P, Whelan CW, Carbone L, Perini G, Mertens F, Rocchi M, Storlazzi CT. Ring chromosomes, breakpoint clusters, and neocentromeres in sarcomas. Genes Chromosomes Cancer 2014; 54:156-67. [PMID: 25421174 DOI: 10.1002/gcc.22228] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 11/03/2014] [Indexed: 01/04/2023] Open
Abstract
Gene amplification is relatively common in tumors. In certain subtypes of sarcoma, it often occurs in the form of ring and/or giant rod-shaped marker (RGM) chromosomes whose mitotic stability is frequently rescued by ectopic novel centromeres (neocentromeres). Little is known about the origin and structure of these RGM chromosomes, including how they arise, their internal organization, and which sequences underlie the neocentromeres. To address these questions, 42 sarcomas with RGM chromosomes were investigated to detect regions prone to double strand breaks and possible functional or structural constraints driving the amplification process. We found nine breakpoint cluster regions potentially involved in the genesis of RGM chromosomes, which turned out to be significantly enriched in poly-pyrimidine traits. Some of the clusters were located close to genes already known to be relevant for sarcomas, thus indicating a potential functional constraint, while others mapped to transcriptionally inactive chromatin domains enriched in heterochromatic sites. Of note, five neocentromeres were identified after analyzing 13 of the cases by fluorescent in situ hybridization. ChIP-on-chip analysis with antibodies against the centromeric protein CENP-A showed that they were a patchwork of small genomic segments derived from different chromosomes, likely joint to form a contiguous sequence during the amplification process.
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Affiliation(s)
- Gemma Macchia
- Department of Biology, University of Bari, Bari, Italy; Department of Clinical Genetics, University and Regional Laboratories, Lund University, Lund, Sweden
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Abstract
The centromere is a specific chromosomal locus that organizes the assembly of the kinetochore. It plays a fundamental role in accurate chromosome segregation. In most eukaryotic organisms, each chromosome contains a single centromere the position and function of which are epigenetically specified. Occasionally, centromeres form at ectopic loci, which can be detrimental to the cell. However, the mechanisms that protect the cell against ectopic centromeres (neocentromeres) remain poorly understood. Centromere protein-A (CENP-A), a centromere-specific histone 3 (H3) variant, is found in all centromeres and is indispensable for centromere function. Here we report that the overexpression of CENP-A(Cnp1) in fission yeast results in the assembly of CENP-A(Cnp1) at noncentromeric chromatin during mitosis and meiosis. The noncentromeric CENP-A preferentially assembles near heterochromatin and is capable of recruiting kinetochore components. Consistent with this, cells overexpressing CENP-A(Cnp1) exhibit severe chromosome missegregation and spindle microtubule disorganization. In addition, pulse induction of CENP-A(Cnp1) overexpression reveals that ectopic CENP-A chromatin can persist for multiple generations. Intriguingly, ectopic assembly of CENP-A(cnp1) is suppressed by overexpression of histone H3 or H4. Finally, we demonstrate that deletion of the N-terminal domain of CENP-A(cnp1) results in an increase in the number of ectopic CENP-A sites and provide evidence that the N-terminal domain of CENP-A prevents CENP-A assembly at ectopic loci via the ubiquitin-dependent proteolysis. These studies expand our current understanding of how noncentromeric chromatin is protected from mistakenly assembling CENP-A.
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Abstract
Centromeres are specialized domains of heterochromatin that provide the foundation for the kinetochore. Centromeric heterochromatin is characterized by specific histone modifications, a centromere-specific histone H3 variant (CENP-A), and the enrichment of cohesin, condensin, and topoisomerase II. Centromere DNA varies orders of magnitude in size from 125 bp (budding yeast) to several megabases (human). In metaphase, sister kinetochores on the surface of replicated chromosomes face away from each other, where they establish microtubule attachment and bi-orientation. Despite the disparity in centromere size, the distance between separated sister kinetochores is remarkably conserved (approximately 1 μm) throughout phylogeny. The centromere functions as a molecular spring that resists microtubule-based extensional forces in mitosis. This review explores the physical properties of DNA in order to understand how the molecular spring is built and how it contributes to the fidelity of chromosome segregation.
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Affiliation(s)
- Kerry S Bloom
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280;
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65
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Subramanian L, Toda NRT, Rappsilber J, Allshire RC. Eic1 links Mis18 with the CCAN/Mis6/Ctf19 complex to promote CENP-A assembly. Open Biol 2014; 4:140043. [PMID: 24789708 PMCID: PMC4043117 DOI: 10.1098/rsob.140043] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CENP-A chromatin forms the foundation for kinetochore assembly. Replication-independent incorporation of CENP-A at centromeres depends on its chaperone HJURPScm3, and Mis18 in vertebrates and fission yeast. The recruitment of Mis18 and HJURPScm3 to centromeres is cell cycle regulated. Vertebrate Mis18 associates with Mis18BP1KNL2, which is critical for the recruitment of Mis18 and HJURPScm3. We identify two novel fission yeast Mis18-interacting proteins (Eic1 and Eic2), components of the Mis18 complex. Eic1 is essential to maintain Cnp1CENP-A at centromeres and is crucial for kinetochore integrity; Eic2 is dispensable. Eic1 also associates with Fta7CENP-Q/Okp1, Cnl2Nkp2 and Mal2CENP-O/Mcm21, components of the constitutive CCAN/Mis6/Ctf19 complex. No Mis18BP1KNL2 orthologue has been identified in fission yeast, consequently it remains unknown how the key Cnp1CENP-A loading factor Mis18 is recruited. Our findings suggest that Eic1 serves a function analogous to that of Mis18BP1KNL2, thus representing the functional counterpart of Mis18BP1KNL2 in fission yeast that connects with a module within the CCAN/Mis6/Ctf19 complex to allow the temporally regulated recruitment of the Mis18/Scm3HJURP Cnp1CENP-A loading factors. The novel interactions identified between CENP-A loading factors and the CCAN/Mis6/Ctf19 complex are likely to also contribute to CENP-A maintenance in other organisms.
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Affiliation(s)
- Lakxmi Subramanian
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3JR, UK
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66
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Mitra S, Gómez-Raja J, Larriba G, Dubey DD, Sanyal K. Rad51-Rad52 mediated maintenance of centromeric chromatin in Candida albicans. PLoS Genet 2014; 10:e1004344. [PMID: 24762765 PMCID: PMC3998917 DOI: 10.1371/journal.pgen.1004344] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 03/19/2014] [Indexed: 11/29/2022] Open
Abstract
Specification of the centromere location in most eukaryotes is not solely dependent on the DNA sequence. However, the non-genetic determinants of centromere identity are not clearly defined. While multiple mechanisms, individually or in concert, may specify centromeres epigenetically, most studies in this area are focused on a universal factor, a centromere-specific histone H3 variant CENP-A, often considered as the epigenetic determinant of centromere identity. In spite of variable timing of its loading at centromeres across species, a replication coupled early S phase deposition of CENP-A is found in most yeast centromeres. Centromeres are the earliest replicating chromosomal regions in a pathogenic budding yeast Candida albicans. Using a 2-dimensional agarose gel electrophoresis assay, we identify replication origins (ORI7-LI and ORI7-RI) proximal to an early replicating centromere (CEN7) in C. albicans. We show that the replication forks stall at CEN7 in a kinetochore dependent manner and fork stalling is reduced in the absence of the homologous recombination (HR) proteins Rad51 and Rad52. Deletion of ORI7-RI causes a significant reduction in the stalled fork signal and an increased loss rate of the altered chromosome 7. The HR proteins, Rad51 and Rad52, have been shown to play a role in fork restart. Confocal microscopy shows declustered kinetochores in rad51 and rad52 mutants, which are evidence of kinetochore disintegrity. CENP-ACaCse4 levels at centromeres, as determined by chromatin immunoprecipitation (ChIP) experiments, are reduced in absence of Rad51/Rad52 resulting in disruption of the kinetochore structure. Moreover, western blot analysis reveals that delocalized CENP-A molecules in HR mutants degrade in a similar fashion as in other kinetochore mutants described before. Finally, co-immunoprecipitation assays indicate that Rad51 and Rad52 physically interact with CENP-ACaCse4in vivo. Thus, the HR proteins Rad51 and Rad52 epigenetically maintain centromere functioning by regulating CENP-ACaCse4 levels at the programmed stall sites of early replicating centromeres. The epigenetic mark of centromeres, CENP-A, is deposited in S phase in most yeasts by a mechanism that is not completely understood. Here, we identify two CEN7 flanking replication origins, ORI7-L1 and ORI7-RI, proximal to an early replicating centromere (CEN7) in a budding yeast Candida albicans. Replication forks starting from these origins stall randomly at CEN7 by the kinetochore that serves as a barrier to fork progression. We observe that centromeric fork stalling is reduced in absence of the HR proteins, Rad51 and Rad52, known to play a role in restarting stalled forks. Further, we demonstrate that Rad51 and Rad52 physically interact with CENP-ACaCse4in vivo. CENP-ACaCse4 levels are reduced in absence of Rad51 or Rad52, which results in disruption of the kinetochore structure. Here we propose a novel DNA replication-coupled mechanism mediated by HR proteins which epigenetically maintains centromere identity by regulating CENP-A deposition. A direct role of DNA repair proteins in centromere function offers insights into the mechanisms of centromere mis-regulation that leads to widespread aneuploidy in cancer cells.
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Affiliation(s)
- Sreyoshi Mitra
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India
| | - Jonathan Gómez-Raja
- Departamento Ciencias Biomédicas Área de Microbiología, Universidad de Extremadura, Badajoz, Spain
| | - Germán Larriba
- Departamento Ciencias Biomédicas Área de Microbiología, Universidad de Extremadura, Badajoz, Spain
| | | | - Kaustuv Sanyal
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India
- * E-mail:
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