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Results for “centromere maintenance”

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Neocentromeres fail to maintain DNA methylation boundaries, driving CENP-A drift, instability, and chromosome missegregation.

Centromere identity is specified by CENP-A, a histone H3 variant that epigenetically defines centromere position. How CENP-A is maintained at one location in rapidly evolving centromeric DNA is unknown. Using single-cell-derived clones of human cell lines, we demonstrate heterogeneity in CENP-A position within cell populations at neocentromeres and a native centromere. CENP-A heterogeneity is accompanied by heterogeneous DNA methylation patterns, with DNA methylation shifting according to CENP-A position. We demonstrate centromere epigenetic plasticity over extended proliferation, with native centromeres maintaining stable DNA methylation boundaries, but neocentromeres exhibiting DNA methylation instability, boundary loss, and increased missegregation. Finally, we show that neocentromeres are more sensitive to DNA methylation inhibition than native centromeres, and that this inhibition is accompanied by expanded CENP-A-enriched domains and increased missegregation. This study supports a role for DNA methylation boundaries in maintaining centromere position, stability, and function and highlights the intrinsic instability of DNA methylation at neocentromeres.

CENP-A

The periphery of nuclear speckles defines a spatially and temporally regulated compartment of long-lived intron-retained RNAs that resolves during mitosis.

RNA localization adds a fundamental layer to gene expression by determining when and where translation-ready mRNAs become available, yet how this timing is coordinated with nuclear architecture and cell-cycle progression remains unclear. Here we identify a subnuclear RNA niche at the nuclear speckle periphery that couples intron retention to cell-cycle-timed RNA release. Using compartment-resolved transcriptional inhibition, sequence-based deep learning and single-molecule and super-resolution RNA imaging in human pluripotent stem cells, we define a class of nuclear RNAs with long-lived retained introns that persist for hours and are enriched in transcripts encoding regulators of genome maintenance and mitosis, including centromere and kinetochore assembly, DNA repair and telomere maintenance. Long-lived retained introns exhibit elevated GC content, predicted structural stability and enrichment for nuclear speckle-associated RNA-binding proteins. In interphase, these RNAs localize to a distinct nuclear speckle-peripheral RNA niche in a spatial arrangement conserved across cell types. During mitotic remodelling, they undergo coordinated, kinase-dependent splicing and are released into the cytoplasm of early G1 daughter cells. Together, these findings link cis-encoded intronic features, subnuclear organization and mitotic remodelling to temporal control of RNA fate.

Mitosis

Preserving centromere identity: right amounts of CENP-A at the right place and time.

Four decades ago, the discovery of centromere protein-A (CENP-A) marked a pivotal breakthrough in chromosome biology, revealing the epigenetic foundation of centromere identity. CENP-A, a histone H3 variant, directs the formation of the microtubule-binding kinetochore complex, designating the chromosomal site for its assembly and underpins the accurate partitioning of genetic material during cell division. Errors in cell division can give rise to DNA instability and aneuploidy, implicated in human diseases such as cancer. Therefore, discovering the underlying pathways and mechanisms responsible for the formation, regulation and maintenance of the centromere is important to our understanding of genome stability, epigenetic inheritance, and in providing the knowledge to help generate possible treatments and therapeutics. Here, we review various molecular pathways and mechanisms implicated in maintaining centromere identity and highlight some of the key outstanding questions with a focus on the human centromere.

Humans

Integrative modeling of the genome structure and dynamics in fission yeast.

Genome organization in the nucleus is highly structured and dynamic. Recent advances in genomic technology have enabled the measurement of genome-wide architecture and locus-specific motion, yielding contact maps and live-cell trajectories. However, these outcomes are derived from different modalities and are not directly comparable, with their quantitative integration being a key challenge. Here we establish a genome-wide live-cell imaging platform in fission yeast Schizosaccharomyces pombe, tracking 131 chromosomal loci, along with the spindle pole body (SPB) and nucleolus, to construct a quantitative map of locus dynamics. By integrating these dynamics with contact data through polymer modeling of Hi-C data, we build a physics-based "digital twin" of the S. pombe genome consistent with the spatiotemporal dynamics of interphase chromatin. We validate it against genome-wide mobility patterns and known architectural features, including centromere and telomere clustering. The model also identifies distinct dynamical regimes: centromere- and telomere-proximal loci relax within [Formula: see text]150 s, whereas the remaining loci relax within [Formula: see text]70 s. We measure semiperiodic dynamics of SPB motion, including a characteristic peak near 225 s and [Formula: see text] fluctuations. We use the model with SPB-directed forcing to show how these low-frequency components propagate through the genome to drive genome-wide chromatin displacements. Together, this predictive physics-based modeling framework integrates genome structure and dynamics to reveal how nuclear mechanical driving forces shape chromosome motion, linking mechanically driven chromatin responses to genome maintenance and regulation.

Schizosaccharomyces