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Dawn M Carone,
Mark S Longo,
Gianni C Ferreri,
Laura Hall,
Melissa Harris,
Nicole Shook, Kira V Bulazel,
Benjamin R Carone,
Craig Obergfell,
Michael J O'Neill,
Rachel J O'Neill
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ABSTRACT: The transcriptional framework of the eukaryotic centromere core has been described in budding yeast and rice, but for most eukaryotes and all vertebrates it remains largely unknown. The lack of large pericentric repeats in the tammar wallaby has made it possible to map and identify the transcriptional units at the centromere in a mammalian species for the first time. We show that these transcriptional units, comprised of satellites and a retrovirus, are bound by centromere proteins and that they are the source of a novel class of small RNA. The endogenous retrovirus from which these small RNAs are derived is now known to be in the centromere domain of several vertebrate classes. The discovery of this new RNA form brings together several independent lines of evidence that point to a conserved retroviral-encoded processed RNA entity within eukaryotic centromeres.
Chromosoma 11/2008; 118(1):113-25. · 3.85 Impact Factor
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ABSTRACT: The constitution of the centromeric portions of the sex chromosomes of the red-necked wallaby, Macropus rufogriseus (family Macropodidae, subfamily Macropodinae), was investigated to develop an overview of the sequence composition of centromeres in a marsupial genome that harbors large amounts of centric and pericentric heterochromatin. The large, C-band-positive centromeric region of the X chromosome was microdissected and the isolated DNA was microcloned. Further sequence and cytogenetic analyses of three representative clones show that all chromosomes in this species carry a 178-bp satellite sequence containing a CENP-B DNA binding domain (CENP-B box) shown herein to selectively bind marsupial CENP-B protein. Two other repeats isolated in this study localize specifically to the sex chromosomes yet differ in copy number and intrachromosomal distribution. Immunocytohistochemistry assays with anti-CENP-E, anti-CREST, anti-CENP-B, and anti-trimethyl-H3K9 antibodies defined a restricted point localization of the outer kinetochore at the functional centromere within an enlarged pericentric and heterochromatic region. The distribution of these repeated sequences within the karyotype of this species, coupled with the apparent high copy number of these sequences, indicates a capacity for retention of large amounts of centromere-associated DNA in the genome of M. rufogriseus.
Genetics 03/2006; 172(2):1129-37. · 4.01 Impact Factor
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Kira. Bulazel
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ABSTRACT: Abstract (2 leaves) bound with copy. Thesis (Ph. D.)--University of Connecticut, 2007. Includes bibliographical references. Adviser: Rachel O'Neill, Dept. of Genetics.
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Kira Bulazel
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ABSTRACT: This thesis endeavors to demonstrate a link between centromere composition and chromosome evolution. The Macropodinae marsupials (wallabies and kangaroos) are uniquely amenable to such study because they have experienced a recent species radiation accompanied by broad karyotypic divergence. To determine whether centromere sequence composition follows the phylogenetic history of species evolution or follows patterns of convergent breakpoint reuse through chromosome evolution, we examined the phylogenetic trajectory of the three representative centromere probes isolated from Macropus rufogriseus . The constitution of the centromeric portions of the sex chromosomes of the red-necked wallaby, Macropus rufogriseus (family Macropodidae), was first investigated to develop an overview of the sequence composition of centromeres within a single marsupial genome. Sequence and cytogenetic analyses of three representative clones showed that they localize specifically to centromeric heterochromatin, yet differ in copy number and intrachromosomal distribution. Immunocytohistochemistry assays defined a restricted, point localization of the functional centromere within the enlarged, pericentric and heterochromatic regions of the M. rufogriseus centromeres. This study identified constituents of the M. rufogriseus chromosomes and developed a more comprehensive overview of the composition of a marsupial centromere. In the second portion of the study the three M. rufogriseus centromere probes were localized to nine species within the Macropus genus. The localization of the three probes was compared with the phylogenetic history of a mitochondrial gene, Cyt b , a nuclear gene, TRSP , and the chromosomal histories of the syntenic blocks that define the different karyotype arrangements. Convergent contraction or expansion of predominant centromere satellites was found to accompany specific karyotype rearrangements. The phylogenetic history of these centromere sequences displayed the convergence of centromere composition in divergent species through convergent breakpoint reuse between syntenic blocks. These data support the "library hypothesis" of centromere evolution within this genus as each species possess the same satellites yet has experienced differential expansion and contraction of these satellites. Thus, we have identified a correlation between the evolution of centromere satellite sequences, the reuse of syntenic break points, and karyotype convergence in the context of a gene-based phylogeny.
ETD Collection for University of Connecticut.
