Organization, Evolution and Function of Alpha Satellite Dna
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ORGANIZATION, EVOLUTION AND FUNCTION OF ALPHA SATELLITE DNA AT HUMAN CENTROMERES by M. KATHARINE RUDD Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Dissertation Advisor: Dr. Huntington F. Willard Department of Genetics CASE WESTERN RESERVE UNIVERSITY January, 2005 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the dissertation of ______________________________________________________ candidate for the Ph.D. degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. 1 Table of Contents Table of contents.................................................................................................1 List of Tables........................................................................................................2 List of Figures......................................................................................................3 Acknowledgements.............................................................................................5 Abstract................................................................................................................6 Chapter 1: Introduction.......................................................................................8 Chapter 2: Analysis of centromeric regions of the human genome.................49 Chapter 3: Alpha satellite evolution in primates: evidence for the homogenization of monomeric alpha satellite................................81 Chapter 4: Human artificial chromosomes with alpha satellite-based de novo centromeres show increased frequency of nondisjunction and anaphase lag................................................................................122 Chapter 5: Conclusions and future studies....................................................155 Appendix: Sequence organization and functional annotation of human centromeres.................................................................................173 Bibliography.....................................................................................................198 2 List of Tables Table 2-1: Alpha satellite in the July 2003 (Build 34) assembly of the human genome..............................................................................62 Table 2-2: Repeat content of the July 2003 (Build 34) human genome assembly........................................................................................77 Table 3-1. Repeat content of the chromosome 17 satellite zone and flanking regions..............................................................................98 Table 3-2. Mean percent identity among monomers from particular regions of alpha satellite...........................................................................102 Table 4-1: Characteristics of human artificial chromosomes.........................135 Table 4-2: Segregation errors........................................................................147 3 List of Figures Figure 1-1: Centromere organization among organisms..................................12 Figure 1-2: Alpha satellite organization at the human centromere...................19 Figure 1-3: Alpha satellite evolution model.......................................................22 Figure 1-4: Centromere and pericentromere model.........................................33 Figure 2-1: Alpha satellite location in the July 2003 (Build 34) human genome assembly..........................................................................61 Figure 2-2: Genomic landscape of 1 Mb regions outside of the centromere gaps................................................................................................64 Figure 2-3: Types of alpha satellite in the human genome...............................68 Figure 2-4: Alpha satellite and centromere protein colocalization....................72 Figure 3-1: Alpha satellite organization in the centromeric region of chromosome 17..............................................................................95 Figure 3-2: Percent identity scores for pairwise comparisons of alpha satellite monomers.......................................................................100 Figure 3-3: Phylogenetic tree of alpha satellite on chromosome 17...............104 Figure 3-4: Neighbor-joining tree of monomers from different chromosomes...............................................................................107 Figure 3-5: Maximum likelihood tree of monomers from different chromosomes...............................................................................109 Figure 3-6: Distributions of interchromosomal and intrachromosomal monomeric monomer percent identities.......................................112 Figure 3-7: Genomic organization of 17q compared to the orthologous Pan troglodytes region.........................................................................115 Figure 4-1: FISH analysis of artificial chromosomes......................................137 4 Figure 4-2: Anaphase segregation assay.......................................................139 Figure 4-3: Missegregation of natural, artificial and variant chromosomes....141 Figure 5-1: Model of alpha satellite evolution.................................................161 Figure 5-2: Strategy for sequencing an entire human centromere.................165 Figure A-1: Alpha satellite organization in the human genome.......................178 Figure A-2: Gaps in the public genome assembly of chromosomes X and 17..........................................................................................181 Figure A-3: Repeat content of the junction between the short arm euchromatin and centromere of the X chromosome.........................................183 Figure A-4: Organization of D17Z1 and D17Z1-B higher-order repeats at the centromere of chromosome 17....................................................185 Figure A-5: Phylogenetic analysis of 230 alpha satellite monomers from the X chromosome and chromosome 17...............................................188 Figure A-6: Functional centromere annotation using a human artificial chromosome assay......................................................................193 Figure A-7: Genome assembly of the centromeric regions of the X chromosome, chromosome 17 and 21.........................................196 5 ACKNOWLEDGEMENTS I would like to thank my advisor, Hunt Willard, for introducing me to alpha satellite and nurturing my scientific development for the past five years. Hunt has made me a better scientist, writer and speaker, and has challenged me to think beyond my view of the chromosome. I am also grateful to Pat Hunt and Terry Hassold. They have been a constant source of support throughout my graduate career, and have always made me feel like a part of their labs. The members of the Willard lab have provided scientific discussion, thoughtful debate, and lots of fun over the years. I am especially grateful to Brenda Grimes and Mary Schueler for educating me in the ways of artificial chromosomes and alpha satellite and for discussing the complex centromere. My friends at Case have been an integral part of my graduate school experience. Whether commiserating over proposal defenses, helping prepare for student seminars, or going out in Coventry to unwind, my friends have always been there for me. My mother and sisters have always encouraged and supported me, even when they weren’t exactly sure what I was doing in the lab. 6 Organization, evolution and function of alpha satellite DNA at human centromeres Abstract by M. KATHARINE RUDD The centromere is a specialized locus responsible for ensuring proper chromosome segregation at mitosis and meiosis. Human centromeres are comprised of large arrays of a primate-specific repeat known as alpha satellite DNA. Understanding the organization and evolution of alpha satellite is essential to delineate the requirements for centromere function. The basic unit of alpha satellite is an ~ 171 bp monomer, and monomers may be organized in one of two types of structure. Higher-order alpha satellite is made up of monomers arranged in homogeneous multimeric higher-order repeat units. In contrast, more divergent monomeric alpha satellite lacks any higher- order periodicity. We have analyzed the alpha satellite in the human genome assembly (Build 34, July 2003), and found regions of both higher-order and monomeric alpha satellite. Although previously identified at all human centromeres, higher-order alpha satellite has only been included in the assemblies of eleven chromosomes. Monomeric alpha satellite typically lies at 7 the edges of larger higher-order arrays, and has been included in all but three chromosome assemblies. The organization of alpha satellite in the human genome is a product of concerted evolutionary processes. We have analyzed the relationships between alpha satellite monomers from multiple chromosomes to discern the exchange mechanisms that have shaped the arrangement of alpha satellite in the genome. Like higher-order alpha satellite described previously, monomeric alpha satellite has a higher frequency of intrachromosomal