CCAN Assembly Configures Composite Binding Interfaces to Promote Cross-Linking of Ndc80 Complexes at the Kinetochore
Ontology highlight
ABSTRACT:
ORGANISM(S): Saccharomyces cerevisiae
PROVIDER: GSE86587 | GEO | 2016/09/09
SECONDARY ACCESSION(S): PRJNA342312
REPOSITORIES: GEO
Similar Datasets
Project description:We use high-resolution chemical cleavage mapping and both native and cross-linked chromatin immunoprecipitation with paired-end sequencing to elucidate the profile of nuceleosomes containing the centromere-specific variant of H3 (cenH3), known as CENP-A or Cnp1 in fission yeast. We find that in the central domain of fission yeast centromeres H3 nucleosomes are nearly absent and CENP-A nucleosomes are more widely spaced that nucleosomes elsewere. CENP-A (Cnp1), CENP-C (Cnp3), CENP-T (Cnp20) and CENP-I (Mis6) are highly enriched at every position in the central domain except at tRNA genes, with weak enrichment in the flanking heterochromatin where these proteins show no evidence of the positioning that has been seen in point centromeres and in the satellite-rich centromeres of plants and animals. Our findings suggest that classical regional centromeres are distinguished from other centromere classes by the absence of cenH3 nucleosome positioning.
2015-08-17 | GSE64294 | GEO
Project description:CENP-A chromatin specifies mammalian centromere identity, and its chaperone HJURP replenishes CENP-A when recruited by the Mis18 complex (Mis18C) via M18BP/KNL2 to CENP-C at kinetochores during interphase. However, the Mis18C recruitment mechanism remains unresolved in species lacking M18BP1, such as fission yeast. Fission yeast centromeres cluster at G2 spindle pole bodies (SPBs) when CENP-ACnp1 is replenished and where Mis18C also localizes. We show that SPBs play an unexpected role in concentrating Mis18C near centromeres through the recruitment of Mis18 by direct binding to the major SPB LInker of Nucleoskeleton and Cytoskeleton (LINC) complex component Sad1. Mis18 recruitment by Sad1 is important for CENP-ACnp1 chromatin establishment and acts in parallel with a CENP-C-mediated Mis18C recruitment pathway to maintain centromeric CENP-ACnp1, but is independent of Sad1-mediated centromere clustering. SPBs therefore provide a non-chromosomal scaffold for both Mis18C recruitment and centromere clustering during G2. This centromere-independent Mis18-SPB recruitment provides a mechanism that governs de novo CENP-ACnp1 chromatin assembly by the proximity of appropriate sequences to SPBs and highlights how nuclear spatial organization influences centromere identity.
2023-09-18 | PXD045191 | Pride
Project description:The centromere is a vital locus on each chromosome which 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, using a combination of biophysical and biochemical analyses we provide evidence for the existence of two populations of structurally distinct CENP-A nucleosomes that co-exist at human centromeres. These two populations display unique sedimentation patterns in a glycerol gradient, and CENP-A nucleosomes that are physically associated with the inner kinetochore appear stabilized in an octameric conformation, with restricted access to the nucleosomal DNA by DNase I. In contrast, the bulk population of CENP-A nucleosomes have diminished heights and weakened DNA interactions. These data suggest that, in vivo, a reserve pool of immature CENP-A nucleosomes exist which wrap DNA loosely, whereas an active inner kinetochore complex associates with stabilized CENP-A nucleosomes. Our data have implications for a function for CENP-A that may be independent of its role in mitotis.
2020-04-02 | GSE129351 | GEO
Project description:Bub1 is required for the kinetochore/centromere localization of two essential mitotic kinases Plk1 and Aurora B. Surprisingly, stable depletion of Bub1 by ~95% in human cells marginally affects whole chromosome segregation fidelity. We show that CENP-U, which is recruited to kinetochores by the CENP-P and CENP-Q subunits of the CENP-O complex, is required to prevent chromosome mis-segregation in Bub1-depleted cells. Mechanistically, Bub1 and CENP-U redundantly recruit Plk1 to kinetochores to stabilize kinetochore-microtubule attachments, thereby ensuring accurate chromosome segregation. Furthermore, unlike its budding yeast homolog, the CENP-O complex does not regulate centromeric localization of Aurora B. Consistently, depletion of Bub1 or CENP-U sensitizes cells to the inhibition of Plk1 but not Aurora B kinase activity. Taken together, our findings provide mechanistic insight into the regulation of kinetochore function, which may have implications for targeted treatment of cancer cells with mutations perturbing kinetochore recruitment of Plk1 by Bub1 or the CENP-O complex.
2021-08-29 | GSE182827 | GEO
Project description:The centromere, defined by the enrichment of CENP-A (a Histone H3 variant) containing nucleosomes, is a specialised chromosomal locus that acts as a microtubule attachment site. To preserve centromere identity, CENP-A levels must be maintained through active CENP-A loading during the cell cycle. A central player mediating this process is the Mis18 complex (Mis18a, Mis18b and Mis18BP1), which recruits the CENP-A specific chaperone HJURP to centromeres for CENP-A deposition. Here, using a multi-pronged approach, we characterise the structure of the Mis18 complex and show that multiple hetero- and homo-oligomeric interfaces facilitate the hetero-octameric Mis18 complex assembly composed of 4 Mis18a, 2 Mis18b and 2 Mis18BP1. Evaluation of structure-guided/separation-of-function mutants reveals structural determinants essential for Mis18 complex assembly and centromere maintenance. Our results provide new mechanistic insights on centromere maintenance, highlighting that while Mis18a can associate with centromeres and deposit CENP-A independently of Mis18b, the latter is indispensable for the optimal level of CENP-A loading required for preserving the centromere identity.
2024-05-15 | PXD047345 | Pride
Project description:The centromere is the location on each chromosome that directs the assembly of the kinetochore. The underlying hallmark of centromeres in most eukaryotes is the presence of specialised nucleosomes in which canonical histone H3 is replaced by the histone H3 variant CENP-A. The molecular events that mediate a programme to install CENP-A in place of histone H3, at centromeres and how the centromeric chromatin is reorganised for CENP-A assembly during cell cycle remain poorly characterised. Histone H2A variant, H2A.Z is linked to transcriptional competence, in maintaining heterochromatin silencing and enriched in CENP-A chromatin. Our analyses demonstrate that H2A.ZPht1 and the Swr1 complex are associated with CENP-ACnp1 chromatin in fission yeast. Swr1 and Msc1 regulate H2A.ZPht1 deposition at centromeres and along with H2A.ZPht1 maintain CENP-ACnp1 chromatin integrity. Additionally, they coordinate the deposition of CENP-ACnp1 through the cell cycle, coupled with eviction of histone H3 from centromeres. Based on our results, we propose that the centromere is programmed to the widespread incorporation of H2A.ZPht1 via Swr1, and that H2A.ZPht1 dynamics likely play a role in regulating centromeric chromatin by influencing CENP-A incorporation.
2020-12-01 | GSE106585 | GEO
Project description:Centromeres are maintained epigenetically by the presence of CENP-A, an evolutionarily-conserved histone H3 variant, which directs kinetochore assembly and hence, centromere function. To identify factors that promote assembly of CENP-A chromatin, we affinity selected solubilised fission yeast CENP-ACnp1 chromatin. All subunits of the Ino80 complex were enriched, including the auxiliary subunit Hap2. In addition to a role in maintenance of CENP-ACnp1 chromatin integrity at endogenous centromeres, Hap2 is required for de novo assembly of CENP-ACnp1 chromatin on naïve centromere DNA and promotes H3 turnover on centromere regions and other loci prone to CENP-ACnp1 deposition. Prior to CENP-ACnp1 chromatin assembly, Hap2 is required for transcription from centromere DNA. These analyses suggest that Hap2-Ino80 destabilises H3 nucleosomes on centromere DNA through transcription-mediated histone H3 turnover, driving the replacement of resident H3 nucleosomes with CENP-ACnp1 nucleosomes. These inherent properties define centromere DNA by directing a program that mediates CENP-ACnp1 assembly on appropriate sequences.
2020-05-27 | PXD016602 | Pride
Project description:Centromeric chromatin is crucial for supporting kinetochore assembly and chromosome segregation. To specify centromeres, the histone H3 variant CENP-A is loaded by the conserved chaperone Scm3/HJURP. The amino-terminus of Scm3/HJURP interacts with CENP-A, while the carboxyl-terminus contains a small domain that interacts with the Mis18 holocomplex, which facilitates centromere localization. Fungal Scm3 proteins contain an additional conserved cysteine-rich domain (CYS) with unknown function. In this study, we found that CYS is essential for the localization and function of fission yeast Scm3. Disrupting CYS prevents Scm3 from localizing to the centromere and results in cell lethality. Moreover, introducing point mutations in a predicted zinc-binding motif within CYS hinders Scm3 centromere targeting and kinetochore integrity, consistent with structural evidence that CYS binds zinc. We find that expressing only the Scm3 carboxyl-terminus is harmful as it localizes to centromeres and causes defective kinetochores. Remarkably, mutating the CYS zinc-binding motif in this construct eliminates the observed centromere localization and toxicity. Together, our findings establish this cysteine-rich domain with predicted zinc-binding capability as an essential feature of fungal Scm3 proteins and shed new light on the molecular mechanism for targeting Scm3 to centromeres.
2024-03-06 | GSE231729 | GEO
Project description:Kinetochores assemble on centromeres via histone H3 variant CENP-A and low levels of noncoding centromere transcripts (cenRNAs). The latter are ensured by transcription factor Cbf1 (S. cerevisiae), centromere-binding protein CENP-B (humans), and the local histone code downregulating RNA polymerase II (RNAPII) activity. CenRNAs levels are further adjusted by the nuclear exosome. Using S. cerevisiae, we now add kinase Rio1 to this scheme. Yeast cenRNAs are produced mostly from the periCEN regions as short (median lengths of 231nt) or long (4,458nt) transcripts, in a 1:1 ratio. Rio1 limits their production by reducing RNAPII access and transcription activity, and promotes their turnover by the 5’-3’exoribonuclease Rat1. Rio1 similarly curtails the concentrations of noncoding pericenRNAs, which nevertheless exist at a magnitude higher level than the cenRNAs. Similar to yeast, human cells depleted of orthologue RioK1 exhibit cenRNA buildup, kinetochore malformation, and chromosomal instability, suggesting that CEN regulation by Rio1/RioK1 is evolutionary conserved.
2023-07-20 | PXD038337 | Pride
Project description:Kinetochores are large proteinaceous structures that assemble on centromeres to align sister chromatids to the mitotic spindle and orchestrate their segregation to the daughter cells. At the core of kinetochores lies a network of proteins known as KMN, whose microtubule-binding activity is regulated by the Ipl1/Aurora B and Mps1 kinases. Here, we have characterized a novel structural yeast kinetochore protein named Cnn1 and show that it regulates KMN-spindle activity by modulating the affinity between the KMN subcomplexes at their basis. Cnn1 supports KMN from S phase to anaphase, and is controlled by the Cdc28, Mps1 and Ipl1 kinases. Cnn1 has evolved to associate the KMN complexes into a coherent network activity to ensure efficient
2012-05-06 | GSE31567 | GEO