bims-micesi 2025-01-05 papers

Nat Commun. 2024 Dec 30. 15(1): 10782

Chk2 sustains PLK1 activity in mitosis to ensure proper chromosome segregation.

Elizabeth M Black, Carlos Andrés Ramírez Parrado, Isabelle Trier, Wenxue Li, Yoon Ki Joo, Jennifer Pichurin, Yansheng Liu, Lilian Kabeche.

Polo-like kinase 1 (PLK1) protects against genome instability by ensuring timely and accurate mitotic cell division, and its activity is tightly regulated throughout the cell cycle. Although the pathways that initially activate PLK1 in G2 are well-characterized, the factors that directly regulate mitotic PLK1 remain poorly understood. Here, we identify that human PLK1 activity is sustained by the DNA damage response kinase Checkpoint kinase 2 (Chk2) in mitosis. Chk2 directly phosphorylates PLK1 T210, a residue on its T-loop whose phosphorylation is essential for full PLK1 kinase activity. Loss of Chk2-dependent PLK1 activity causes increased mitotic errors, including chromosome misalignment, chromosome missegregation, and cytokinetic defects. Moreover, Chk2 deficiency increases sensitivity to PLK1 inhibitors, suggesting that Chk2 status may be an informative biomarker for PLK1 inhibitor efficacy. This work demonstrates that Chk2 sustains mitotic PLK1 activity and protects genome stability through discrete functions in interphase DNA damage repair and mitotic chromosome segregation.

DOI: https://doi.org/10.1038/s41467-024-54922-7

Cell Div. 2024 Dec 28. 19(1): 36

PP2A-Tws dephosphorylates Map205, is required for Polo localization to microtubules and promotes cytokinesis in Drosophila.

Marine Guelle, Virginie Emond-Fraser, Vincent Archambault.

BACKGROUND: Mitosis and cytokinesis are regulated by reversible phosphorylation events controlled by kinases and phosphatases. Drosophila Polo kinase, like its human ortholog PLK1, plays several roles in this process. Multiple mechanisms contribute to regulate Polo/PLK1 activity, localization and interactions. We previously showed that the microtubule-associated protein Map205 interacts with Polo during interphase and cytokinesis, inhibiting and sequestering Polo on microtubules. During mitosis, phosphorylation of Map205 at a Cyclin-Dependent Kinase site allows Polo to dissociate from Map205, when Polo must fulfill its mitotic functions. How the Polo/Map205 interaction is restored during mitotic exit remained unknown.
RESULTS: Here we show that PP2A-Tws/B55 is required to dephosphorylate Map205, and enables the Map205-dependent localization of Polo to microtubules during cytokinesis. In addition, we show that PP2A-Tws is required for spindle function during cytokinesis, consistent with the essential role of Polo in this process.
CONCLUSIONS: These findings complement previous studies to provide an understanding of the full cycle of Polo regulation by Map205, kinases and phosphatases. Our findings have implications for the wider network of cell cycle regulatory circuitry.

Keywords: Drosophila ; Cell cycle; Cytokinesis; Map205; Mitosis; PP2A-B55; Polo; Tws

DOI: https://doi.org/10.1186/s13008-024-00141-x

Andrology. 2024 Dec 30.

CENP-E haploinsufficiency causes chromosome misalignment and spindle assembly checkpoint activation in the spermatogonia.

Jie Chen, Jie-Jie He, Shan Wu, Zhao-Yang Deng, Yu-Peng Liu, Jian-Fan Chen, Yue Xu, Han-Kai Fang, Ya-Lan Wei, Zhen-Yu She.

BACKGROUND: The establishment of kinetochore-microtubule attachment is essential for error-free chromosome alignment and segregation during cell division. Defects in chromosome alignment result in chromosome instability, birth defects, and infertility. Kinesin-7 CENP-E mediates kinetochore-microtubule capture, chromosome alignment, and spindle assembly checkpoint in somatic cells, however, mechanisms of CENP-E in germ cells remain poorly understood.
OBJECTIVES: This study aimed to explore the functions of CENP-E in the proliferation and self-renewal of spermatogonia.
MATERIALS AND METHODS: A CENP-E heterozygous knockout strain was established in C57BL/6J mice using the CRISPR/Cas9 and Cre/LoxP system. Hematoxylin-eosin staining was performed to study the histology. The inhibition of CENP-E in the GC-1 spg cells was performed using the specific inhibitor GSK923295. The expression and localization of spermatogonial marker proteins were determined by immunofluorescence using confocal microscopy in the control and CENP-E+/- heterozygous mouse testes. The protein expression level was analyzed using Western blot. The cell-cycle and apoptosis assay were measured using flow cytometry. In addition, karyotype analysis was performed using hypotonic preparation and chromosome spreading.
RESULTS: Here, we reveal that CENP-E haploinsufficiency results in chromosome misalignment, spindle disorganization, and metaphase arrest in spermatogonia, which leads to the loss of spermatogonia, chromosomal instability, and spermatogenic disorders. Notably, CENP-E ablation leads to the activation of spindle assembly checkpoint and aneuploidy, which impairs the proliferation and self-renewal of spermatogonia.
DISCUSSION AND CONCLUSION: CENP-E depletion disrupts the recruitment of key checkpoint proteins, including BubR1, Bub1, KIF2C, and Aurora B, indicating a causal relationship between chromosome misalignment and spindle assembly checkpoint activation in spermatogonia. Our findings demonstrate that CENP-E regulates kinetochore-microtubule attachment, chromosome alignment, and spindle assembly checkpoint in spermatogonia.

Keywords: CENP‐E; chromosome alignment; kinesin; spermatogonia; spindle assembly checkpoint

DOI: https://doi.org/10.1111/andr.13834

Nat Commun. 2025 Jan 02. 16(1): 307

Targeting chromosomally unstable tumors with a selective KIF18A inhibitor.

Chromosome instability is a prevalent vulnerability of cancer cells that has yet to be fully exploited therapeutically. To identify genes uniquely essential to chromosomally unstable cells, we mined the Cancer Dependency Map for genes essential in tumor cells with high levels of copy number aberrations. We identify and validate KIF18A, a mitotic kinesin, as a vulnerability of chromosomally unstable cancer cells. Knockdown of KIF18A leads to mitotic defects and reduction of tumor growth. Screening of a chemical library for inhibitors of KIF18A enzymatic activity identified a hit that was optimized to yield VLS-1272, which is orally bioavailable, potent, ATP non-competitive, microtubule-dependent, and highly selective for KIF18A versus other kinesins. Inhibition of KIF18A's ATPase activity prevents KIF18A translocation across the mitotic spindle, resulting in chromosome congression defects, mitotic cell accumulation, and cell death. Profiling VLS-1272 across >100 cancer cell lines demonstrates that the specificity towards cancer cells with chromosome instability differentiates KIF18A inhibition from other clinically tested anti-mitotic drugs. Treatment of tumor xenografts with VLS-1272 results in mitotic defects leading to substantial, dose-dependent inhibition of tumor growth. The strong biological rationale, robust preclinical data, and optimized compound properties enable the clinical development of a KIF18A inhibitor in cancers with high chromosomal instability.

DOI: https://doi.org/10.1038/s41467-024-55300-z

J Mol Cell Biol. 2025 Jan 02. pii: mjae062. [Epub ahead of print]

Phosphorylation of CENP-C by PLK1 ensures accurate chromosome congression during mitosis.

Shanshan He, Cunyu Wang, Hengyi Shao, Chengcheng Hu, Ranran Hu, Ran Liu, Chuanhai Fu, Xing Liu, Xuebiao Yao, Liangyu Zhang.

DOI: https://doi.org/10.1093/jmcb/mjae062

J Mol Cell Biol. 2025 Jan 02. pii: mjae059. [Epub ahead of print]

Microtubule plus-end tracking protein EB1 orchestrates mitotic progression via liquid-liquid phase separation.

Mengjie Li, Ming Dai, Xing Hong, Yunze Li, Xiyu Wang, Yini Lin, Tahir Ullah, Yuxin Zhu, Kai Jiang, Zhikai Wang, Zhonghuai Hou, Kai Zhang, Xuebiao Yao, Xiaoyu Song, Xing Liu.

DOI: https://doi.org/10.1093/jmcb/mjae059

Nat Cell Biol. 2024 Dec 30.

TRACERx analysis identifies a role for FAT1 in regulating chromosomal instability and whole-genome doubling via Hippo signalling.

TRACERx Consortium

Chromosomal instability (CIN) is common in solid tumours and fuels evolutionary adaptation and poor prognosis by increasing intratumour heterogeneity. Systematic characterization of driver events in the TRACERx non-small-cell lung cancer (NSCLC) cohort identified that genetic alterations in six genes, including FAT1, result in homologous recombination (HR) repair deficiencies and CIN. Using orthogonal genetic and experimental approaches, we demonstrate that FAT1 alterations are positively selected before genome doubling and associated with HR deficiency. FAT1 ablation causes persistent replication stress, an elevated mitotic failure rate, nuclear deformation and elevated structural CIN, including chromosome translocations and radial chromosomes. FAT1 loss contributes to whole-genome doubling (a form of numerical CIN) through the dysregulation of YAP1. Co-depletion of YAP1 partially rescues numerical CIN caused by FAT1 loss but does not relieve HR deficiencies, nor structural CIN. Importantly, overexpression of constitutively active YAP15SA is sufficient to induce numerical CIN. Taken together, we show that FAT1 loss in NSCLC attenuates HR and exacerbates CIN through two distinct downstream mechanisms, leading to increased tumour heterogeneity.

DOI: https://doi.org/10.1038/s41556-024-01558-w