scholarly journals Both tails and the centromere targeting domain of CENP-A are required for centromere establishment

2015 ◽  
Vol 208 (5) ◽  
pp. 521-531 ◽  
Author(s):  
Glennis A. Logsdon ◽  
Evelyne J. Barrey ◽  
Emily A. Bassett ◽  
Jamie E. DeNizio ◽  
Lucie Y. Guo ◽  
...  
Keyword(s):  
Cell Division ◽  
Histone H3 ◽  
Lac Repressor ◽  
Chromosomal Locus ◽  
Gain Of Function ◽  
Lac Operator ◽  
Centromere Proteins ◽  
Histone H3 Variant ◽  
Segregation Of Chromosomes

The centromere—defined by the presence of nucleosomes containing the histone H3 variant, CENP-A—is the chromosomal locus required for the accurate segregation of chromosomes during cell division. Although the sequence determinants of human CENP-A required to maintain a centromere were reported, those that are required for early steps in establishing a new centromere are unknown. In this paper, we used gain-of-function histone H3 chimeras containing various regions unique to CENP-A to investigate early events in centromere establishment. We targeted histone H3 chimeras to chromosomally integrated Lac operator sequences by fusing each of the chimeras to the Lac repressor. Using this approach, we found surprising contributions from a small portion of the N-terminal tail and the CENP-A targeting domain in the initial recruitment of two essential constitutive centromere proteins, CENP-C and CENP-T. Our results indicate that the regions of CENP-A required for early events in centromere establishment differ from those that are required for maintaining centromere identity.

scholarly journals CENP-A nucleosome—a chromatin-embedded pedestal for the centromere: lessons learned from structural biology

2020 ◽  
Vol 64 (2) ◽  
pp. 205-221
Author(s):  
Ahmad Ali-Ahmad ◽  
Nikolina Sekulić
Keyword(s):  
Cell Division ◽  
Structural Biology ◽  
Histone H3 ◽  
Lessons Learned ◽  
Centromeric Chromatin ◽  
Centromere Proteins ◽  
Molecular Determinants ◽  
Histone H3 Variant ◽  
Segregation Of Chromosomes

Abstract The centromere is a chromosome locus that directs equal segregation of chromosomes during cell division. A nucleosome containing the histone H3 variant CENP-A epigenetically defines the centromere. Here, we summarize findings from recent structural biology studies, including several CryoEM structures, that contributed to elucidate specific features of the CENP-A nucleosome and molecular determinants of its interactions with CENP-C and CENP-N, the only two centromere proteins that directly bind to it. Based on those findings, we propose a role of the CENP-A nucleosome in the organization of centromeric chromatin beyond binding centromeric proteins.

scholarly journals Effective Potentials and Orbits in Weyl Conformastatic Slender Disk

2021 ◽  
Author(s):  
Paul Talbert ◽  
Steven Henikoff
Keyword(s):  
Cell Division ◽  
Dna Sequences ◽  
Histone H3 ◽  
Repeated Dna ◽  
Sequencing Technology ◽  
Repeated Dna Sequences ◽  
Effective Potentials ◽  
Histone H3 Variant ◽  
Long Read ◽  
Chromosomal Loci

Centromeres, the chromosomal loci where spindle fibers attach during cell division to segregate chromosomes, are typically found within satellite arrays in plants and animals. Satellite arrays have been difficult to analyze because they comprise megabases of tandem head-to-tail highly repeated DNA sequences. Much evidence suggests that centromeres are epigenetically defined by the location of nucleosomes containing the centromere-specific histone H3 variant cenH3, independently of the DNA sequences where they are located; however, the reason that cenH3 nucleosomes are generally found on rapidly evolving satellite arrays has remained unclear. Recently, long read sequencing technology has clarified the structures of satellite arrays and sparked rethinking of how they evolve, while new experiments and analyses have helped bring both understanding and further speculation about the role these highly repeated sequences play in centromere identification.

scholarly journals Recurrent loss of CenH3 is associated with independent transitions to holocentricity in insects

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Ines A Drinnenberg ◽  
Dakota deYoung ◽  
Steven Henikoff ◽  
Harmit Singh Malik
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Chromosomal Region ◽  
Histone H3 ◽  
The Other ◽  
Spindle Attachment ◽  
Histone H3 Variant ◽  
Transcriptome Analyses ◽  
Almost All ◽  
Chromosomal Length

Faithful chromosome segregation in all eukaryotes relies on centromeres, the chromosomal sites that recruit kinetochore proteins and mediate spindle attachment during cell division. The centromeric histone H3 variant, CenH3, is the defining chromatin component of centromeres in most eukaryotes, including animals, fungi, plants, and protists. In this study, using detailed genomic and transcriptome analyses, we show that CenH3 was lost independently in at least four lineages of insects. Each of these lineages represents an independent transition from monocentricity (centromeric determinants localized to a single chromosomal region) to holocentricity (centromeric determinants extended over the entire chromosomal length) as ancient as 300 million years ago. Holocentric insects therefore contain a CenH3-independent centromere, different from almost all the other eukaryotes. We propose that ancient transitions to holocentricity in insects obviated the need to maintain CenH3, which is otherwise essential in most eukaryotes, including other holocentrics.

scholarly journals The Prolylhydroxylase PHD2 Modulates Centromere Function through the Hydroxylation of CENP-N

2015 ◽  
Author(s):  
Sandra C Moser ◽  
Dalila Bensaddek ◽  
Brian Ortmann ◽  
Sonia Rocha ◽  
Angus I Lamond ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Protein Complexes ◽  
Histone H3 ◽  
Attachment Site ◽  
Deficient Mutant ◽  
Multiprotein Complex ◽  
Centromere Function ◽  
Spindle Poles ◽  
Histone H3 Variant ◽  
Segregation Of Chromosomes

Successful segregation of chromosomes during mitosis requires that each sister chromatid is captured by microtubules emanating from opposite spindle poles. A multiprotein complex called the kinetochore provides an attachment site on chromosomes for microtubules. We have found that the prolylhydroxylase PHD2 is a critical regulator of the assembly of the kinetochore. PHD2 hydroxylates the kinetochore component CENP-N on P311 and is essential for CENP-N localization to kinetochores. Either depletion of PHD2, or expression of a hydroxylation-deficient mutant, results in loss of the histone H3 variant CENP-A from centromeres. Loss of CENP-N from chromatin bound protein complexes is not due to decreased protein stability but is a consequence of lowered affinity of CENP-N for binding CENP-L. Loss of hydroxylation also results in increased targeting of CENP-L to chromatin. Hydroxylation by PHD2 thus plays an important role in controlling the stoichiometry of mitotic kinetochore components.

scholarly journals Epigenetic inheritance of centromere identity in a heterologous system

2019 ◽  
Author(s):  
Virginie Roure ◽  
Bethan Medina-Pritchard ◽  
Eduard Anselm ◽  
A. Arockia Jeyaprakash ◽  
Patrick Heun
Keyword(s):  
Chromosome Segregation ◽  
Chromosomal Region ◽  
Histone H3 ◽  
Epigenetic Inheritance ◽  
Centromeric Chromatin ◽  
Centromere Proteins ◽  
Heterologous System ◽  
Histone H3 Variant ◽  
Self Association

SUMMARYThe centromere is an essential chromosomal region required for accurate chromosome segregation. Most eukaryotic centromeres are defined epigenetically by the histone H3 variant, CENP-A, yet how its self-propagation is achieved remains poorly understood. Here we developed a heterologous system to reconstitute epigenetic inheritance of centromeric chromatin by ectopically targeting the Drosophila centromere proteins dCENP-A, dCENP-C and CAL1 to LacO arrays in human cells. Dissecting the function of these three components uncovers the key role of self-association of dCENP-C and CAL1 for their mutual interaction and dCENP-A deposition. Importantly, we identify the components required for dCENP-C loading onto chromatin, involving a cooperation between CAL1 and dCENP-A nucleosomes, thus closing the epigenetic loop to ensure dCENP-C and dCENP-A replenishment during the cell division cycle. Finally, we show that all three Drosophila factors are sufficient for dCENP-A propagation and propose a model for the epigenetic inheritance of centromere identity.

scholarly journals CENP-C recruits M18BP1 to centromeres to promote CENP-A chromatin assembly

2011 ◽  
Vol 194 (6) ◽  
pp. 855-871 ◽  
Author(s):  
Ben Moree ◽  
Corey B. Meyer ◽  
Colin J. Fuller ◽  
Aaron F. Straight
Keyword(s):  
Chromosome Segregation ◽  
Protein A ◽  
Histone H3 ◽  
Chromatin Assembly ◽  
Nucleosome Assembly ◽  
Chromosomal Locus ◽  
C Protein ◽  
Centromere Protein A ◽  
Histone H3 Variant ◽  
Complex Protein

Eukaryotic chromosomes segregate by attaching to microtubules of the mitotic spindle through a chromosomal microtubule binding site called the kinetochore. Kinetochores assemble on a specialized chromosomal locus termed the centromere, which is characterized by the replacement of histone H3 in centromeric nucleosomes with the essential histone H3 variant CENP-A (centromere protein A). Understanding how CENP-A chromatin is assembled and maintained is central to understanding chromosome segregation mechanisms. CENP-A nucleosome assembly requires the Mis18 complex and the CENP-A chaperone HJURP. These factors localize to centromeres in telophase/G1, when new CENP-A chromatin is assembled. The mechanisms that control their targeting are unknown. In this paper, we identify a mechanism for recruiting the Mis18 complex protein M18BP1 to centromeres. We show that depletion of CENP-C prevents M18BP1 targeting to metaphase centromeres and inhibits CENP-A chromatin assembly. We find that M18BP1 directly binds CENP-C through conserved domains in the CENP-C protein. Thus, CENP-C provides a link between existing CENP-A chromatin and the proteins required for new CENP-A nucleosome assembly.

scholarly journals The ratio between centromeric proteins CENP-A and CENP-C maintains homeostasis of human centromeres

2019 ◽  
Author(s):  
Daniël P. Melters ◽  
Tatini Rakshit ◽  
Minh Bui ◽  
Sergei A. Grigoryev ◽  
David Sturgill ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
De Novo ◽  
Histone H3 ◽  
Chromosomal Locus ◽  
Centromeric Chromatin ◽  
Dna Accessibility ◽  
Nucleosome Dynamics ◽  
Histone H3 Variant ◽  
Correct Ratio

AbstractThe centromere is the chromosomal locus that seeds the kinetochore, allowing for a physical connection between the chromosome and the mitotic spindle. At the heart of the centromere is the centromere-specific histone H3 variant CENP-A/CENH3. Throughout the cell cycle the constitutive centromere associated network is bound to CENP-A chromatin, but how this protein network modifies CENP-A nucleosome dynamics in vivo is unknown. Here, we purify kinetochore associated native centromeric chromatin and analyze its biochemical features using a combinatorial approach. We report that kinetochore bound chromatin has strongly reduced DNA accessibility and a distinct stabilized nucleosomal configuration. Disrupting the balance between CENP-A and CENP-C result in reduced centromeric occupancy of RNA polymerase 2 and impaired de novo CENP-A loading on the centromeric chromatin fiber, correlating with significant mitotic defects. CENP-A mutants that restore the ratio rescue the mitotic defects. These data support a model in which CENP-C bound centromeric nucleosomes behave as a barrier to the transcriptional machinery and suggest that maintaining the correct ratio between CENP-A and CENP-C levels is critical for centromere homeostasis.

The nucleosomes that mark centromere location on chromosomes old and new

2019 ◽  
Vol 63 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Craig W. Gambogi ◽  
Ben E. Black
Keyword(s):  
Dna Sequences ◽  
Critical Role ◽  
Histone H3 ◽  
Centromeric Dna ◽  
Artificial Chromosomes ◽  
Centromere Function ◽  
Histone H3 Variant ◽  
Dna Elements ◽  
Mitosis And Meiosis ◽  
Segregation Of Chromosomes

Abstract Proper segregation of chromosomes is an essential component of cell division. The centromere is the locus at which the kinetochore—the proteinaceous complex that ties chromosomes to microtubules—forms during mitosis and meiosis. Thus, the centromere is critical for equal segregation of chromosomes. The centromere is characterized by both protein and DNA elements: the histone H3 variant CENP-A epigenetically defines the location of the centromere while centromeric DNA sequences are neither necessary nor sufficient for centromere function. Paradoxically, the DNA sequences play a critical role in new centromere formation. In this essay, we discuss the contribution of both epigenetics and genetics at the centromere. Understanding these contributions is vital to efforts to control centromere formation on synthetic/artificial chromosomes and centromere strength on natural ones.

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