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1.  Adaptive Evolution of Foundation Kinetochore Proteins in Primates 
Molecular Biology and Evolution  2010;27(7):1585-1597.
Rapid evolution is a hallmark of centromeric DNA in eukaryotic genomes. Yet, the centromere itself has a conserved functional role that is mediated by the kinetochore protein complex. To broaden our understanding about both the DNA and proteins that interact at the functional centromere, we sought to gain a detailed view of the evolutionary events that have shaped the primate kinetochore. Specifically, we performed comparative mapping and sequencing of the genomic regions encompassing the genes encoding three foundation kinetochore proteins: Centromere Proteins A, B, and C (CENP-A, CENP-B, and CENP-C). A histone H3 variant, CENP-A provides the foundation of the centromere-specific nucleosome. Comparative sequence analyses of the CENP-A gene in 14 primate species revealed encoded amino-acid residues within both the histone-fold domain and the N-terminal tail that are under strong positive selection. Similar comparative analyses of CENP-C, another foundation protein essential for centromere function, identified amino-acid residues throughout the protein under positive selection in the primate lineage, including several in the centromere localization and DNA-binding regions. Perhaps surprisingly, the gene encoding CENP-B, a kinetochore protein that binds specifically to alpha-satellite DNA, was not found to be associated with signatures of positive selection. These findings point to important and distinct evolutionary forces operating on the DNA and proteins of the primate centromere.
doi:10.1093/molbev/msq043
PMCID: PMC2912471  PMID: 20142441
kinetochore; selection; evolution; centromere
2.  Histone Modifications within the Human X Centromere Region 
PLoS ONE  2009;4(8):e6602.
Human centromeres are multi-megabase regions of highly ordered arrays of alpha satellite DNA that are separated from chromosome arms by unordered alpha satellite monomers and other repetitive elements. Complexities in assembling such large repetitive regions have limited detailed studies of centromeric chromatin organization. However, a genomic map of the human X centromere has provided new opportunities to explore genomic architecture of a complex locus. We used ChIP to examine the distribution of modified histones within centromere regions of multiple X chromosomes. Methylation of H3 at lysine 4 coincided with DXZ1 higher order alpha satellite, the site of CENP-A localization. Heterochromatic histone modifications were distributed across the 400–500 kb pericentromeric regions. The large arrays of alpha satellite and gamma satellite DNA were enriched for both euchromatic and heterochromatic modifications, implying that some pericentromeric repeats have multiple chromatin characteristics. Partial truncation of the X centromere resulted in reduction in the size of the CENP-A/Cenp-A domain and increased heterochromatic modifications in the flanking pericentromere. Although the deletion removed ∼1/3 of centromeric DNA, the ratio of CENP-A to alpha satellite array size was maintained in the same proportion, suggesting that a limited, but defined linear region of the centromeric DNA is necessary for kinetochore assembly. Our results indicate that the human X centromere contains multiple types of chromatin, is organized similarly to smaller eukaryotic centromeres, and responds to structural changes by expanding or contracting domains.
doi:10.1371/journal.pone.0006602
PMCID: PMC2719913  PMID: 19672304
3.  The DNA sequence of the human X chromosome 
Ross, Mark T. | Grafham, Darren V. | Coffey, Alison J. | Scherer, Steven | McLay, Kirsten | Muzny, Donna | Platzer, Matthias | Howell, Gareth R. | Burrows, Christine | Bird, Christine P. | Frankish, Adam | Lovell, Frances L. | Howe, Kevin L. | Ashurst, Jennifer L. | Fulton, Robert S. | Sudbrak, Ralf | Wen, Gaiping | Jones, Matthew C. | Hurles, Matthew E. | Andrews, T. Daniel | Scott, Carol E. | Searle, Stephen | Ramser, Juliane | Whittaker, Adam | Deadman, Rebecca | Carter, Nigel P. | Hunt, Sarah E. | Chen, Rui | Cree, Andrew | Gunaratne, Preethi | Havlak, Paul | Hodgson, Anne | Metzker, Michael L. | Richards, Stephen | Scott, Graham | Steffen, David | Sodergren, Erica | Wheeler, David A. | Worley, Kim C. | Ainscough, Rachael | Ambrose, Kerrie D. | Ansari-Lari, M. Ali | Aradhya, Swaroop | Ashwell, Robert I. S. | Babbage, Anne K. | Bagguley, Claire L. | Ballabio, Andrea | Banerjee, Ruby | Barker, Gary E. | Barlow, Karen F. | Barrett, Ian P. | Bates, Karen N. | Beare, David M. | Beasley, Helen | Beasley, Oliver | Beck, Alfred | Bethel, Graeme | Blechschmidt, Karin | Brady, Nicola | Bray-Allen, Sarah | Bridgeman, Anne M. | Brown, Andrew J. | Brown, Mary J. | Bonnin, David | Bruford, Elspeth A. | Buhay, Christian | Burch, Paula | Burford, Deborah | Burgess, Joanne | Burrill, Wayne | Burton, John | Bye, Jackie M. | Carder, Carol | Carrel, Laura | Chako, Joseph | Chapman, Joanne C. | Chavez, Dean | Chen, Ellson | Chen, Guan | Chen, Yuan | Chen, Zhijian | Chinault, Craig | Ciccodicola, Alfredo | Clark, Sue Y. | Clarke, Graham | Clee, Chris M. | Clegg, Sheila | Clerc-Blankenburg, Kerstin | Clifford, Karen | Cobley, Vicky | Cole, Charlotte G. | Conquer, Jen S. | Corby, Nicole | Connor, Richard E. | David, Robert | Davies, Joy | Davis, Clay | Davis, John | Delgado, Oliver | DeShazo, Denise | Dhami, Pawandeep | Ding, Yan | Dinh, Huyen | Dodsworth, Steve | Draper, Heather | Dugan-Rocha, Shannon | Dunham, Andrew | Dunn, Matthew | Durbin, K. James | Dutta, Ireena | Eades, Tamsin | Ellwood, Matthew | Emery-Cohen, Alexandra | Errington, Helen | Evans, Kathryn L. | Faulkner, Louisa | Francis, Fiona | Frankland, John | Fraser, Audrey E. | Galgoczy, Petra | Gilbert, James | Gill, Rachel | Glöckner, Gernot | Gregory, Simon G. | Gribble, Susan | Griffiths, Coline | Grocock, Russell | Gu, Yanghong | Gwilliam, Rhian | Hamilton, Cerissa | Hart, Elizabeth A. | Hawes, Alicia | Heath, Paul D. | Heitmann, Katja | Hennig, Steffen | Hernandez, Judith | Hinzmann, Bernd | Ho, Sarah | Hoffs, Michael | Howden, Phillip J. | Huckle, Elizabeth J. | Hume, Jennifer | Hunt, Paul J. | Hunt, Adrienne R. | Isherwood, Judith | Jacob, Leni | Johnson, David | Jones, Sally | de Jong, Pieter J. | Joseph, Shirin S. | Keenan, Stephen | Kelly, Susan | Kershaw, Joanne K. | Khan, Ziad | Kioschis, Petra | Klages, Sven | Knights, Andrew J. | Kosiura, Anna | Kovar-Smith, Christie | Laird, Gavin K. | Langford, Cordelia | Lawlor, Stephanie | Leversha, Margaret | Lewis, Lora | Liu, Wen | Lloyd, Christine | Lloyd, David M. | Loulseged, Hermela | Loveland, Jane E. | Lovell, Jamieson D. | Lozado, Ryan | Lu, Jing | Lyne, Rachael | Ma, Jie | Maheshwari, Manjula | Matthews, Lucy H. | McDowall, Jennifer | McLaren, Stuart | McMurray, Amanda | Meidl, Patrick | Meitinger, Thomas | Milne, Sarah | Miner, George | Mistry, Shailesh L. | Morgan, Margaret | Morris, Sidney | Müller, Ines | Mullikin, James C. | Nguyen, Ngoc | Nordsiek, Gabriele | Nyakatura, Gerald | O’Dell, Christopher N. | Okwuonu, Geoffery | Palmer, Sophie | Pandian, Richard | Parker, David | Parrish, Julia | Pasternak, Shiran | Patel, Dina | Pearce, Alex V. | Pearson, Danita M. | Pelan, Sarah E. | Perez, Lesette | Porter, Keith M. | Ramsey, Yvonne | Reichwald, Kathrin | Rhodes, Susan | Ridler, Kerry A. | Schlessinger, David | Schueler, Mary G. | Sehra, Harminder K. | Shaw-Smith, Charles | Shen, Hua | Sheridan, Elizabeth M. | Shownkeen, Ratna | Skuce, Carl D. | Smith, Michelle L. | Sotheran, Elizabeth C. | Steingruber, Helen E. | Steward, Charles A. | Storey, Roy | Swann, R. Mark | Swarbreck, David | Tabor, Paul E. | Taudien, Stefan | Taylor, Tineace | Teague, Brian | Thomas, Karen | Thorpe, Andrea | Timms, Kirsten | Tracey, Alan | Trevanion, Steve | Tromans, Anthony C. | d’Urso, Michele | Verduzco, Daniel | Villasana, Donna | Waldron, Lenee | Wall, Melanie | Wang, Qiaoyan | Warren, James | Warry, Georgina L. | Wei, Xuehong | West, Anthony | Whitehead, Siobhan L. | Whiteley, Mathew N. | Wilkinson, Jane E. | Willey, David L. | Williams, Gabrielle | Williams, Leanne | Williamson, Angela | Williamson, Helen | Wilming, Laurens | Woodmansey, Rebecca L. | Wray, Paul W. | Yen, Jennifer | Zhang, Jingkun | Zhou, Jianling | Zoghbi, Huda | Zorilla, Sara | Buck, David | Reinhardt, Richard | Poustka, Annemarie | Rosenthal, André | Lehrach, Hans | Meindl, Alfons | Minx, Patrick J. | Hillier, LaDeana W. | Willard, Huntington F. | Wilson, Richard K. | Waterston, Robert H. | Rice, Catherine M. | Vaudin, Mark | Coulson, Alan | Nelson, David L. | Weinstock, George | Sulston, John E. | Durbin, Richard | Hubbard, Tim | Gibbs, Richard A. | Beck, Stephan | Rogers, Jane | Bentley, David R.
Nature  2005;434(7031):325-337.
The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y, and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence.
doi:10.1038/nature03440
PMCID: PMC2665286  PMID: 15772651
4.  Comparative sequence analyses reveal sites of ancestral chromosomal fusions in the Indian muntjac genome 
Genome Biology  2008;9(10):R155.
Comparative mapping and sequencing was used to characterize the sites of ancestral chromosomal fusions in the Indian muntjac genome.
Background
Indian muntjac (Muntiacus muntjak vaginalis) has an extreme mammalian karyotype, with only six and seven chromosomes in the female and male, respectively. Chinese muntjac (Muntiacus reevesi) has a more typical mammalian karyotype, with 46 chromosomes in both sexes. Despite this disparity, the two muntjac species are morphologically similar and can even interbreed to produce viable (albeit sterile) offspring. Previous studies have suggested that a series of telocentric chromosome fusion events involving telomeric and/or satellite repeats led to the extant Indian muntjac karyotype.
Results
We used a comparative mapping and sequencing approach to characterize the sites of ancestral chromosomal fusions in the Indian muntjac genome. Specifically, we screened an Indian muntjac bacterial artificial-chromosome library with a telomere repeat-specific probe. Isolated clones found by fluorescence in situ hybridization to map to interstitial regions on Indian muntjac chromosomes were further characterized, with a subset then subjected to shotgun sequencing. Subsequently, we isolated and sequenced overlapping clones extending from the ends of some of these initial clones; we also generated orthologous sequence from isolated Chinese muntjac clones. The generated Indian muntjac sequence has been analyzed for the juxtaposition of telomeric and satellite repeats and for synteny relationships relative to other mammalian genomes, including the Chinese muntjac.
Conclusions
The generated sequence data and comparative analyses provide a detailed genomic context for seven ancestral chromosome fusion sites in the Indian muntjac genome, which further supports the telocentric fusion model for the events leading to the unusual karyotypic differences among muntjac species.
doi:10.1186/gb-2008-9-10-r155
PMCID: PMC2760882  PMID: 18957082

Results 1-4 (4)