bims-micesi 2025-10-19 papers

Issue of 2025–10–19
six papers selected by
Valentina Piano, Uniklinik Köln

Mol Oncol. 2025 Oct 12.

Survivin and Aurora Kinase A control cell fate decisions during mitosis.

Hana Abdelkabir, Shalitha Wickrama Arachchige, Sally P Wheatley.

The spindle assembly checkpoint (SAC) delays the metaphase-to-anaphase transition. Aurora kinase A (AURKA) inactivation has been shown to cause premature exit from mitosis in the presence of an unsatisfied SAC. We report for the first time that centromeric AURKA interacts with survivin during prometaphase. Notably, depleting or inhibiting AURKA activity at this stage causes mislocalisation of the CPC and BubR1, which compromises the SAC and can lead to mitotic slippage. Furthermore, we show that AURKA binds directly to the BIR domain of survivin at a position distinct from AURKB and indirectly to it via its C terminus. We find the interaction peaks during prometaphase but persists into late mitosis. Importantly, we demonstrate that cells with high levels of survivin are particularly vulnerable to mitotic slippage induced by the AURKA inhibitor, MLN8237/ Alisertib. Alisertib enables both normal and transformed cells with high levels of survivin to activate the APC/C prematurely, as observed by the destruction of cyclin B and securin. Thus, a high expression of survivin can alter cell fate decisions at mitosis and lead to genetic instability, a key hallmark in cancer.

Keywords: aurora kinase; chromosomal passenger complex (CPC); mitosis; mitotic slippage; spindle assembly checkpoint (SAC); survivin

DOI: https://doi.org/10.1002/1878-0261.70141

Nucleic Acids Res. 2025 Oct 14. pii: gkaf1038. [Epub ahead of print]53(19):

Direct observation of interdependent and hierarchical kinetochore assembly on individual centromeres.

Changkun Hu, Andrew R Popchock, Angelica Andrade Latino, Charles L Asbury, Sue Biggins.

Kinetochores are megadalton protein machines that harness microtubules to segregate chromosomes during cell division. The kinetochores must assemble after DNA replication during every cell cycle onto specialized regions of chromosomes called centromeres, but the order and regulation of their assembly remains unclear due to the complexity of kinetochore composition and the difficulty resolving individual kinetochores in vivo. Here, by adapting a prior single-molecule method for monitoring kinetochore assembly in budding yeast lysates, we identify a sequential order of assembly and uncover previously unknown interdependencies between subcomplexes. We show that inner kinetochore assembly depends partly on outer kinetochore components, and that outer kinetochore branches do not assemble independently of one another. Notably, Mif2 assembly is a rate-limiting step that can be accelerated by binding to the Mtw1 subcomplex, thereby promoting rapid assembly of many inner and outer kinetochore components. The importance of controlling kinetochore assembly kinetics is supported by a Mif2 mutant lacking both autoinhibition and Mtw1 subcomplex binding activity, which leads to defective kinetochore-microtubule attachments when the centromeric histone variant Cse4 is overexpressed. Altogether, our work provides a direct view of kinetochore assembly and reveals highly interdependent regulatory events that control its order and timing.

DOI: https://doi.org/10.1093/nar/gkaf1038

Chromosome Res. 2025 Oct 16. 33(1): 22

The dynamic centromere.

Angela Enriquez, Yael Nechemia-Arbely.

Centromeres are fundamental chromosomal structures that ensure accurate chromosome segregation during cell division. Despite their conserved and essential role in maintaining genomic stability, centromeres are subject to rapid evolutionary change. At the heart of centromere identity is the histone H3 variant CENP-A, an epigenetic mark that defines and propagates active centromeres and is essential for their function. Recent evidence supports a rapid evolution of centromere DNA sequences but also suggests a certain degree of flexibility in CENP-A deposition and propagation. The phenomenon of centromere drift, recently observed in humans, highlights how the dynamic repositioning of CENP-A and associated epigenetic environment over time maintains a regulated equilibrium, ensuring centromere function despite positional variation. Understanding these processes is crucial for unraveling centromere dynamics and their broader implications for genome stability and evolution.

Keywords: CENP-A; Centromeres; Chromatin; Epigenetics; Evolution; Mitosis

DOI: https://doi.org/10.1007/s10577-025-09779-x

Nat Struct Mol Biol. 2025 Oct 17.

Dynamics of microcompartment formation at the mitosis-to-G1 transition.

Viraat Y Goel, Nicholas G Aboreden, James M Jusuf, Haoyue Zhang, Luisa P Mori, Leonid A Mirny, Gerd A Blobel, Edward J Banigan, Anders S Hansen.

As cells exit mitosis and enter G1, chromosomes decompact and transcription is reestablished. Hi-C studies have indicated that all interphase three-dimensional genome features, including A/B compartments, topologically associating domains and CCCTC-binding factor loops, are lost during mitosis. However, Hi-C is insensitive to features such as microcompartments, nested focal interactions between cis-regulatory elements. Here we apply region capture Micro-C to mouse erythroblasts from mitosis to G1. We unexpectedly observe microcompartments in prometaphase, which strengthen in anaphase and telophase before weakening throughout G1. Microcompartment anchors coincide with transcriptionally spiking promoters during mitosis. Loss of condensin loop extrusion differentially impacts microcompartments and A/B compartments, suggesting that they are partially distinct. Polymer modeling shows that microcompartment formation is favored by chromatin compaction and disfavored by loop extrusion, providing a basis for strong microcompartmentalization in anaphase and telophase. Our results suggest that compaction and homotypic affinity drive microcompartment formation, which may explain transient transcriptional spiking at mitotic exit.

DOI: https://doi.org/10.1038/s41594-025-01687-2

Chromosoma. 2025 Oct 15. 134(1): 9

Phosphorylation as a regulatory mechanism of HP1 protein multifunctionality.

James C Walts, Nicole C Riddle.

The Heterochromatin Protein 1 (HP1) family proteins are key regulators of chromatin structure and genome function, acting as "reader" proteins that recognize and bind to histone H3 lysine 9 methylation (H3K9me). Beyond their canonical role in heterochromatin formation and transcriptional repression, HP1 proteins exhibit functional versatility, participating in transcriptional activation, RNA processing, DNA repair, and chromosome segregation. This multifunctionality is mediated partially by post-translational modifications (PTMs), with phosphorylation emerging as a central regulatory mechanism. This review explores the diverse effects of HP1 phosphorylation on protein function and chromatin interactions, focusing on Drosophila melanogaster HP1a and its orthologs, mammalian HP1α and S. pombe Swi6. Phosphorylation in the N-terminal tail enhances HP1's affinity for H3K9me, promoting transcriptional silencing. Mitotic phosphorylation of serine residues in the hinge region, regulated by kinases such as AURKB and NDR1/2, leads to chromatin release and relocalization to the kinetochore, enabling proper chromosome segregation. Additionally, phosphorylation modulates HP1 phase separation dynamics, influencing nuclear compartmentalization and chromatin condensation. These findings highlight phosphorylation as a versatile molecular switch that enables HP1 proteins to transition between structural and regulatory roles, contributing to their evolutionary conserved multifunctionality in genome regulation and cell division. Further investigation into HP1 phosphorylation across species and contexts is essential to fully understand its contributions to chromatin biology.

Keywords: Chromatin; Drosophila; Gene regulation; HP1; Heterochromatin; Post-translational modifications

DOI: https://doi.org/10.1007/s00412-025-00838-0

J Vis Exp. 2025 Sep 26.

Manipulation and Analysis of Cell Cycle-Dependent Processes in Budding Yeast.

Michael G Stewart, Talia C Scheel, Ahmed A Abouelghar, Sara E Hoppe, Matthew P Miller.

Eukaryotic cells follow a conserved cell cycle that regulates diverse processes, including DNA maintenance and organelle homeostasis. Studying cellular processes in a cell cycle-dependent manner is often necessary to properly interpret experimental results. There are chemical and genetic methods available to produce cell cycle synchronization in cultured cells across a wide swath of organisms, including vertebrate models, enabling the study of cell cycle-dependent processes. However, among model organisms, budding yeast remains a powerhouse for cell cycle analysis due to its particularly robust synchronization methods, short generation time, and genetic tractability. Yeast shares core cell cycle machinery with other eukaryotes, which has enabled landmark discoveries in cell cycle regulation. This protocol details methods for cell cycle analysis in yeast, focusing on G1 arrest-release and mitotic arrest-release experiments, including strain construction, culture preparation, and microscopy. PCR tagging methods for producing suitable strains for cell cycle arrests and fluorescence microscopy are presented. A G1 arrest is achieved using the peptide pheromone α-factor, and brief washes result in synchronous release and cell cycle progression. Samples are taken at different time points following release into the cell cycle and fixed for microscopy. A second method arrests yeast cells in mitosis by depleting the cell cycle regulator Cdc20 to achieve a metaphase-arrested population, as well as optional release into anaphase. Samples are fixed and prepared for imaging pre- and post-release, and are imaged and analyzed. Image analysis focuses on cataloging dynamic localization and population abundance changes of proteins in the cell cycle. These synchronization methods are suitable for diverse cell cycle manipulations, and while their use in imaging fixed cells is highlighted here, they can be adapted for many other analyses, including live cell imaging as well as biochemical and molecular assays.

DOI: https://doi.org/10.3791/68887