bims-micesi 2024-01-21 papers

bims-micesi

Biomed News

on Mitotic cell signalling

Issue of 2024‒01‒21
nine papers selected by
Valentina Piano, Uniklinik Köln

Contribution of CENP-F to FOXM1-mediated discordant centromere and kinetochore transcriptional regulation.
The LINC complex ensures accurate centrosome positioning during prophase.
Sculpting nuclear envelope identity from the endoplasmic reticulum during the cell cycle.
Regulation of centrosome size by the cell-cycle oscillator in Drosophila embryos.
COX6C expression driven by copy amplification of 8q22.2 regulates cell proliferation via mediation of mitosis by ROS-AMPK signaling in lung adenocarcinoma.
RNF20 Regulates Oocyte Meiotic Spindle Assembly by Recruiting TPM3 to Centromeres and Spindle Poles.
Live-cell imaging defines a threshold in CDK activity at the G2/M transition.
Transient excited states of the metamorphic protein Mad2 and their implications for function.
Evidence for novel mechanisms that control cell cycle entry and cell size.

bioRxiv. 2023 Dec 27. pii: 2023.12.27.573453. [Epub ahead of print]

Contribution of CENP-F to FOXM1-mediated discordant centromere and kinetochore transcriptional regulation.

Sakshi Khurana, Daniel R Foltz.

Proper chromosome segregation is required to ensure genomic and chromosomal stability. The centromere is a unique chromatin domain present throughout the cell cycle on each chromosome defined by the CENP-A nucleosome. Centromeres (CEN) are responsible for recruiting the kinetochore (KT) during mitosis, ultimately regulating spindle attachment and mitotic checkpoint function. Upregulation of many genes that encode the CEN/KT proteins is commonly observed in cancer. Here, we show although that FOXM1 occupies the promoters of many CEN/KT genes with MYBL2, occupancy is insufficient alone to drive the FOXM1 correlated transcriptional program. We show that CENP-F, a component of the outer kinetochore, functions with FOXM1 to coregulate G2/M transcription and proper chromosome segregation. Loss of CENP-F results in alteration of chromatin accessibility at G2/M genes, including CENP-A, and leads to reduced FOXM1-MBB complex formation. The FOXM1-CENP-F transcriptional coordination is a cancer-specific function. We observed that a few CEN/KT genes escape FOXM1 regulation such as CENP-C which when upregulated with CENP-A, leads to increased chromosome misegregation and cell death. Together, we show that the FOXM1 and CENP-F coordinately regulate G2/M gene expression, and this coordination is specific to a subset of genes to allow for proliferation and maintenance of chromosome stability for cancer cell survival.

DOI: https://doi.org/10.1101/2023.12.27.573453
Life Sci Alliance. 2024 Apr;pii: e202302404. [Epub ahead of print]7(4):

The LINC complex ensures accurate centrosome positioning during prophase.

Joana T Lima, António J Pereira, Jorge G Ferreira.

Accurate centrosome separation and positioning during early mitosis relies on force-generating mechanisms regulated by a combination of extracellular, cytoplasmic, and nuclear cues. The identity of the nuclear cues involved in this process remains largely unknown. Here, we investigate how the prophase nucleus contributes to centrosome positioning during the initial stages of mitosis, using a combination of cell micropatterning, high-resolution live-cell imaging, and quantitative 3D cellular reconstruction. We show that in untransformed RPE-1 cells, centrosome positioning is regulated by a nuclear signal, independently of external cues. This nuclear mechanism relies on the linker of nucleoskeleton and cytoskeleton complex that controls the timely loading of dynein on the nuclear envelope (NE), providing spatial cues for robust centrosome positioning on the shortest nuclear axis, before nuclear envelope permeabilization. Our results demonstrate how nuclear-cytoskeletal coupling maintains a robust centrosome positioning mechanism to ensure efficient mitotic spindle assembly.

DOI: https://doi.org/10.26508/lsa.202302404
Nucleus. 2024 Dec;15(1): 2299632

Sculpting nuclear envelope identity from the endoplasmic reticulum during the cell cycle.

Pallavi Deolal, Julia Scholz, Kaike Ren, Helena Bragulat-Teixidor, Shotaro Otsuka.

  The nuclear envelope (NE) regulates nuclear functions, including transcription, nucleocytoplasmic transport, and protein quality control. While the outer membrane of the NE is directly continuous with the endoplasmic reticulum (ER), the NE has an overall distinct protein composition from the ER, which is crucial for its functions. During open mitosis in higher eukaryotes, the NE disassembles during mitotic entry and then reforms as a functional territory at the end of mitosis to reestablish nucleocytoplasmic compartmentalization. In this review, we examine the known mechanisms by which the functional NE reconstitutes from the mitotic ER in the continuous ER-NE endomembrane system during open mitosis. Furthermore, based on recent findings indicating that the NE possesses unique lipid metabolism and quality control mechanisms distinct from those of the ER, we explore the maintenance of NE identity and homeostasis during interphase. We also highlight the potential significance of membrane junctions between the ER and NE.

Keywords:  Cell cycle; ER–NE junction; endoplasmic reticulum; mitosis; nuclear assembly; nuclear envelope; nuclear pore complex

DOI:  https://doi.org/10.1080/19491034.2023.2299632
EMBO J. 2024 Jan 17.

Regulation of centrosome size by the cell-cycle oscillator in Drosophila embryos.

Siu-Shing Wong, Alan Wainman, Saroj Saurya, Jordan W Raff.

  Mitotic centrosomes assemble when centrioles recruit large amounts of pericentriolar material (PCM) around themselves. In early C. elegans embryos, mitotic centrosome size appears to be set by the limiting amount of a key component. In Drosophila syncytial embryos, thousands of mitotic centrosomes are assembled as the embryo proceeds through 13 rounds of rapid nuclear division, driven by a core cell cycle oscillator. These divisions slow during nuclear cycles 11-13, and we find that centrosomes respond by reciprocally decreasing their growth rate, but increasing their growth period-so that they grow to a relatively consistent size at each cycle. At the start of each cycle, moderate CCO activity initially promotes centrosome growth, in part by stimulating Polo/PLK1 recruitment to centrosomes. Later in each cycle, high CCO activity inhibits centrosome growth by suppressing the centrosomal recruitment and/or maintenance of centrosome proteins. Thus, in fly embryos, mitotic centrosome size appears to be regulated predominantly by the core cell cycle oscillator, rather than by the depletion of a limiting component.

Keywords:  Cell Cycle; Centriole; Centrosome; Organelle Size; PCM

DOI:  https://doi.org/10.1038/s44318-023-00022-z
Cell Death Dis. 2024 Jan 19. 15(1): 74

COX6C expression driven by copy amplification of 8q22.2 regulates cell proliferation via mediation of mitosis by ROS-AMPK signaling in lung adenocarcinoma.

Shuanghui Liu, Fanggui Shao, Yourong Wang, Yurui Zhang, Hongjia Yu, Ningxin Zhang, Lan He, Qingran Kong, Hao Jiang, Zhixiong Dong.

Copy number variations (CNVs) play a vital role in regulating genes expression and tumorigenesis. We explored the copy number alterations in early-stage lung adenocarcinoma using high-throughput sequencing and nucleic acid flight mass spectrometry technology, and found that 8q22.1-22.2 is frequently amplified in lung adenocarcinoma tissues. COX6C localizes on the region and its expression is notably enhanced that driven by amplification in lung adenocarcinoma. Knockdown of COX6C significantly inhibits the cell proliferation, and induces S-G2/M cell cycle arrest, mitosis deficiency and apoptosis. Moreover, COX6C depletion causes a deficiency in mitochondrial fusion, and impairment of oxidative phosphorylation. Mechanistically, COX6C-induced mitochondrial deficiency stimulates ROS accumulation and activates AMPK pathway, then leading to abnormality in spindle formation and chromosome segregation, activating spindle assemble checkpoint, causing mitotic arrest, and ultimately inducing cell apoptosis. Collectively, we suggested that copy amplification-mediated COX6C upregulation might serves as a prospective biomarker for prognosis and targeting therapy in patients with lung adenocarcinoma.

DOI: https://doi.org/10.1038/s41419-024-06443-w
Adv Sci (Weinh). 2024 Jan 19. e2306986

RNF20 Regulates Oocyte Meiotic Spindle Assembly by Recruiting TPM3 to Centromeres and Spindle Poles.

Liying Wang, Chao Liu, Li Li, Huafang Wei, Wei Wei, Qiuxing Zhou, Yinghong Chen, Tie-Gang Meng, Renjie Jiao, Zhen-Bo Wang, Qing-Yuan Sun, Wei Li.

  Previously a ring finger protein 20 (RNF20) is found to be essential for meiotic recombination and mediates H2B ubiquitination during spermatogenesis. However, its role in meiotic division is still unknown. Here, it is shown that RNF20 is localized at both centromeres and spindle poles, and it is required for oocyte acentrosomal spindle organization and female fertility. RNF20-depleted oocytes exhibit severely abnormal spindle and chromosome misalignment caused by defective bipolar organization. Notably, it is found that the function of RNF20 in spindle assembly is not dependent on its E3 ligase activity. Instead, RNF20 regulates spindle assembly by recruiting tropomyosin3 (TPM3) to both centromeres and spindle poles with its coiled-coil motif. The RNF20-TPM3 interaction is essential for acentrosomal meiotic spindle assembly. Together, the studies uncover a novel function for RNF20 in mediating TPM3 recruitment to both centromeres and spindle poles during oocyte spindle assembly.

Keywords:  RNF20; TPM3; meiosis; oocyte maturation; spindle assembly

DOI:  https://doi.org/10.1002/advs.202306986
Dev Cell. 2024 Jan 08. pii: S1534-5807(23)00695-0. [Epub ahead of print]

Live-cell imaging defines a threshold in CDK activity at the G2/M transition.

Hironori Sugiyama, Yuhei Goto, Yohei Kondo, Damien Coudreuse, Kazuhiro Aoki.

  Cyclin-dependent kinase (CDK) determines the temporal ordering of the cell cycle phases. However, despite significant progress in studying regulators of CDK and phosphorylation patterns of CDK substrates at the population level, it remains elusive how CDK regulators coordinately affect CDK activity at the single-cell level and how CDK controls the temporal order of cell cycle events. Here, we elucidate the dynamics of CDK activity in fission yeast and mammalian cells by developing a CDK activity biosensor, Eevee-spCDK. We find that although CDK activity does not necessarily correlate with cyclin levels, it converges to the same level around mitotic onset in several mutant backgrounds, including pom1Δ cells and wee1 or cdc25 overexpressing cells. These data provide direct evidence that cells enter the M phase when CDK activity reaches a high threshold, consistent with the quantitative model of cell cycle progression in fission yeast.

Keywords:  Cdc25; FRET; Pom1; Wee1; cell cycle; cell size; cyclin-dependent kinase; fission yeast; imaging; phosphatase

DOI:  https://doi.org/10.1016/j.devcel.2023.12.014
Proteins. 2024 Jan 14.

Transient excited states of the metamorphic protein Mad2 and their implications for function.

Shefali Jain, Ashok Sekhar.

  The spindle checkpoint complex is a key surveillance mechanism in cell division that prevents premature separation of sister chromatids. Mad2 is an integral component of this spindle checkpoint complex that recognizes cognate substrates such as Mad1 and Cdc20 in its closed (C-Mad2) conformation by fastening a "seatbelt" around short peptide regions that bind to the substrate recognition site. Mad2 is also a metamorphic protein that adopts not only the fold found in C-Mad2, but also a structurally distinct open conformation (O-Mad2) which is incapable of binding substrates. Here, we show using chemical exchange saturation transfer (CEST) and relaxation dispersion (CPMG) NMR experiments that Mad2 transiently populates three other higher free energy states with millisecond lifetimes, two in equilibrium with C-Mad2 (E1 and E2) and one with O-Mad2 (E3). E1 is a mimic of substrate-bound C-Mad2 in which the N-terminus of one C-Mad2 molecule inserts into the seatbelt region of a second molecule of C-Mad2, providing a potential pathway for autoinhibition of C-Mad2. E2 is the "unbuckled" conformation of C-Mad2 that facilitates the triage of molecules along competing fold-switching and substrate binding pathways. The E3 conformation that coexists with O-Mad2 shows fluctuations at a hydrophobic lock that is required for stabilizing the O-Mad2 fold and we hypothesize that E3 represents an early intermediate on-pathway towards conversion to C-Mad2. Collectively, the NMR data highlight the rugged free energy landscape of Mad2 with multiple low-lying intermediates that interlink substrate-binding and fold-switching, and also emphasize the role of molecular dynamics in its function.

Keywords:  Carr-Purcell-Meiboom-Gill relaxation dispersion; Mad2; chemical exchange saturation transfer; excited states; metamorphic proteins; protein dynamics; protein function

DOI:  https://doi.org/10.1002/prot.26667
Mol Biol Cell. 2024 Jan 17. mbcE23050174

Evidence for novel mechanisms that control cell cycle entry and cell size.

Amanda Brambila, Beth E Prichard, Jerry T DeWitt, Douglas R Kellogg.

Entry into the cell cycle in late G1 phase occurs only when sufficient growth has occurred. In budding yeast, a cyclin called Cln3 is thought to link cell cycle entry to cell growth. Cln3 accumulates during growth in early G1 phase and eventually helps trigger expression of late G1 phase cyclins that drive cell cycle entry. All current models for cell cycle entry assume that expression of late G1 phase cyclins is initiated at the transcriptional level. Current models also assume that the sole function of Cln3 in cell cycle entry is to promote transcription of late G1 phase cyclins, and that Cln3 works solely in G1 phase. Here, we show that cell cycle-dependent expression of the late G1 phase cyclin Cln2 does not require any functions of the CLN2 promoter. Moreover, Cln3 can influence accumulation of Cln2 protein via post-transcriptional mechanisms. Finally, we show that Cln3 has functions in mitosis that strongly influence cell size. Together, these discoveries reveal the existence of surprising new mechanisms that challenge current models for control of cell cycle entry and cell size.

DOI: https://doi.org/10.1091/mbc.E23-05-0174