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The causality between DNA methylation changes and mitosis can be bidirectional, conditioned on biochemical, genomic, cellular, and developmental factors. Replicative epimutations contribute to aging and age-related diseases like cancer through various mechanisms, acting as passengers, drivers, or both. Replicative epimutation serves as a mechanism underlying epigenetic clocks. Epigenetic editing enables a systematic identification of epimutations affecting replicative systems. The mitotic inheritability of DNA methylation as an epigenetic marker in higher-order eukaryotes has been established for >40 years. The DNA methylome and mitotic division interplay is now considered bidirectional and highly intertwined. Various epigenetic writers, erasers, and modulators shape the perceived replicative methylation dynamics. This Review surveys the principles and complexity of mitotic transmission of DNA methylation, emphasizing the awareness of mitotic aging in analyzing DNA methylation dynamics in development and disease. We reviewed how DNA methylation changes alter mitotic proliferation capacity, implicating age-related diseases like cancer. We link replicative epimutation to stem cell dysfunction, inflammatory response, cancer risks, and epigenetic clocks, discussing the causative role of DNA methylation in health and disease. [ABSTRACT FROM AUTHOR]

Exportin-1 (XPO1) is well established for its role in nuclear export. Selective inhibitors of nuclear export have been approved by the FDA for treatment of hematologic cancers, and the therapeutic implication of targeting XPO1 in other cancers is an active area of research. Although the majority of XPO1 literature centers on its nuclear export function, emerging studies highlight additional cellular activities for XPO1, including in the formation of nuclear condensates and coordination of transcriptional events. Next-generation chemical tools offer future therapeutic and investigative potential beyond nuclear export and oncology by selectively targeting some of XPO1's cellular roles. Exportin-1 (XPO1), also known as chromosome region maintenance 1 (CRM1), directly binds to and mediates the nuclear export of hundreds of cargo proteins. Blocking nuclear export by the selective inhibitors of nuclear export (SINEs) is a validated therapeutic axis in cancer and an active area of research. However, a growing body of evidence implicates XPO1 in biological functions beyond nuclear export that include the regulation of mitosis and the epigenome. Additionally, new pharmacological classes of small molecules have emerged that degrade XPO1 or induce distinct cellular activity profiles. Here, we discuss the canonical model of nuclear export and XPO1's emergence as an anticancer target. We also spotlight the key evidence for underappreciated XPO1 functions and discuss the use of chemical probes to uncover new cellular roles for XPO1. With these growing trends, the field is poised to extend XPO1 therapeutic targeting to indications beyond oncology. [ABSTRACT FROM AUTHOR]

To ensure an even segregation of chromosomes during somatic cell division, eukaryotes rely on mitotic spindles. Here, we measured prime characteristics of the Arabidopsis mitotic spindle and built a three-dimensional dynamic model using Cytosim. We identified the cell-cycle regulator CYCLIN-DEPENDENT KINASE B1 (CDKB1) together with its cyclin partner CYCB3;1 as key regulators of spindle morphology in Arabidopsis. We found that the augmin component ENDOSPERM DEFECTIVE1 (EDE1) is a substrate of the CDKB1;1-CYCB3;1 complex. A non-phosphorylatable mutant rescue of ede1 resembled the spindle phenotypes of cycb3;1 and cdkb1 mutants and the protein associated less efficiently with spindle microtubules. Accordingly, reducing the level of augmin in simulations recapitulated the phenotypes observed in the mutants. Our findings emphasize the importance of cell-cycle-dependent phospho-control of the mitotic spindle in plant cells and support the validity of our model as a framework for the exploration of mechanisms controlling the organization of the eukaryotic spindle. [Display omitted] • Generation of a 3D simulation of the Arabidopsis spindle • B1-type CDKs together with a B3-type cyclin control spindle morphology via augmin • The requirement of augmin for spindle morphology is recapitulated by 3D simulations Romeiro Motta et al. show that spindle morphology is controlled by the phosphorylation of augmin performed by a cell-cycle regulator complex in Arabidopsis. By constructing a tridimensional simulation of the Arabidopsis mitotic spindle, combined with several experimental approaches, they show that changes in augmin activity largely impact spindle organization. [ABSTRACT FROM AUTHOR]

The Allium cepa assay is a valuable tool for evaluating natural products as potential anticancer agents by monitoring mitosis progression in onion root tips. However, the traditional method of identifying and classifying cells into various mitotic stages, and categorizing them as either dividing or non-dividing cells to calculate the mitotic index, can be laborious and prone to mistakes. This study aims to streamline the process of computing for the mitotic index using a convolutional neural network to identify and classify cells into different mitotic stages, and categorize them as dividing and non-dividing cells. A dataset of 1548 high-quality images of onion root tip cells displaying different stages of mitosis was used. A pretrained YOLOv8 model achieved an 88.33% mean average precision and 83% recall. Experiment results show that this approach can reduce the time-consuming aspects of the assay and potentially accelerate laboratory experiments performed in the search for novel anticancer drugs. [ABSTRACT FROM AUTHOR]

The relationship between O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and mitosis is intertwined. Besides the numerous mitotic OGT substrates that have been identified, OGT itself is also a target of the mitotic machinery. Previously, our investigations have shown that Checkpoint kinase 1 (Chk1) phosphorylates OGT at Ser-20 to increase OGT levels during cytokinesis, suggesting that OGT levels oscillate as mitosis progresses. Herein we studied its underlying mechanism. We set out from an R17C mutation of OGT, which is a uterine carcinoma mutation in The Cancer Genome Atlas. We found that R17C abolishes the S20 phosphorylation of OGT, as it lies in the Chk1 phosphorylating consensus motif. Consistent with our previous report that pSer-20 is essential for OGT level increases during cytokinesis, we further demonstrate that the R17C mutation renders OGT less stable, decreases vimentin phosphorylation levels and results in cytokinesis defects. Based on bioinformatic predictions, pSer-20 renders OGT more likely to interact with 14-3-3 proteins, the phospho-binding signal adaptor/scaffold protein family. By screening the seven isoforms of 14-3-3 family, we show that 14-3-3e specifically associates with Ser-20-phosphorylated OGT. Moreover, we studied the R17C and S20A mutations in xenograft models and demonstrated that they both inhibit uterine carcinoma compared to wild-type OGT, probably due to less cellular reproduction. Our work is a sequel of our previous report on pS20 of OGT and is in line with the notion that OGT is intricately regulated by the mitotic network. [ABSTRACT FROM AUTHOR]

Hybrid vigor in plants confers better agronomically significant traits in offspring compared with either parent. Recently, Wang et al. reported a mitosis instead of meiosis (MiMe) system in tomato for clonal gamete production, showing the potential to exploit autopolyploid progressive heterosis by stacking genomes from four grandparents in tetraploid hybrids, developed from crossing MiMe hybrids. [ABSTRACT FROM AUTHOR]

Transcription factor (TF) IIH is a factor involved in transcription, DNA repair, mitosis, and telomere stability. These functions stem from its helicase/ATPase and kinase activities. Recent reports on the structure and function of the transcription machinery, as well as chromosome compaction during mitosis, suggest that TFIIH also influences nucleosome movement, are explored here. [ABSTRACT FROM AUTHOR]

Alterations in cell cycle regulation contribute to Zika virus (ZIKV)-associated pathogenesis and may have implications for the development of therapeutic avenues. As a matter of fact, ZIKV alters cell cycle progression at multiple stages, including G1, S, G2, and M phases. During a cell cycle, the progression of mitosis is particularly controlled to avoid any abnormalities in cell division. In this regard, the critical metaphase-anaphase transition is triggered by the activation of anaphase-promoting complex/cyclosome (APC/C) by its E3 ubiquitin ligase subunit Cdc20. Cdc20 recognizes substrates by interacting with a destruction box motif (D-box). Recently, the ZIKV nonstructural protein 5 (NS5), one of the most highly conserved flavivirus proteins, has been shown to localize to the centrosome in each pole and to spindle fibers during mitosis. Inducible expression of NS5 reveals an interaction of this viral factor with centrosomal proteins leading to an increase in the time required to complete mitosis. By analyzing the NS5 sequence, we discovered the presence of a D-box. Taken together, these data support the idea that, in addition to its role in viral replication, NS5 plays a critical role in the control of the cell cycle of infected cells and, more specifically, in the regulation of the mitotic spindle. Here we propose that the NS5 protein may interfere with the metaphase-anaphase progression, and thus cause the observed delay in mitosis via the regulation of APC/C. • ZIKV NS5 regulates mitosis progression. • ZIKV NS5 has a potential D-box. • The presence of D-box suggests a regulation of APC/cyclosome by NS5. [ABSTRACT FROM AUTHOR]

There is dynamic and bidirectional regulation of cell metabolism and cell cycle progression that is incompletely understood. Changes to cellular metabolism, including redox state, can directly affect the activity of cell cycle regulators and signaling pathways to impact cell cycle control. Mitochondrial metabolism changes dramatically during the cell cycle and most acutely during mitosis. Cells adjust cell cycle duration and growth rate to couple cell size to cell cycle progression and maintain uniform cell size across generations. Disruption of protein synthesis or DNA replication can drive cells to exit the cell cycle and become quiescent. The relationship between metabolism and cell cycle progression is complex and bidirectional. Cells must rewire metabolism to meet changing biosynthetic demands across cell cycle phases. In turn, metabolism can influence cell cycle progression through direct regulation of cell cycle proteins, through nutrient-sensing signaling pathways, and through its impact on cell growth, which is linked to cell division. Furthermore, metabolism is a key player in mediating quiescence–proliferation transitions in physiologically important cell types, such as stem cells. How metabolism impacts cell cycle progression, exit, and re-entry, as well as how these processes impact metabolism, is not fully understood. Recent advances uncovering mechanistic links between cell cycle regulators and metabolic processes demonstrate a complex relationship between metabolism and cell cycle control, with many questions remaining. [ABSTRACT FROM AUTHOR]

The single unit nature of the mitochondrial genome (kinetoplast DNA; kDNA) of trypanosomes requires precise mechanisms that guarantee the segregation of the duplicated kDNA during cytokinesis. Segregation of the duplicated kDNA during cytokinesis depends on the tripartite attachment complex (TAC), which physically links the basal body (BB) of the flagellum with the kDNA. Much progress has been made in identifying the molecular core subunits of the TAC and how they interact with each other, allowing formulation of a model of TAC architecture that explains how the TAC connects the BB across the mitochondrial membranes with the kDNA. Recent studies highlight how individual TAC subunits are imported into mitochondria, sorted to, and integrated into, the TAC, illustrating the central role of the mitochondrial outer membrane TAC module in the assembly process. A comparative analysis between the TAC and the mitotic spindle reveals conserved features and concepts shared between these DNA segregation complexes. The tripartite attachment complex (TAC) of the single mitochondrion of trypanosomes allows precise segregation of its single nucleoid mitochondrial genome during cytokinesis. It couples the segregation of the duplicated mitochondrial genome to the segregation of the basal bodies of the flagella. Here, we provide a model of the molecular architecture of the TAC that explains how its eight essential subunits connect the basal body, across the mitochondrial membranes, with the mitochondrial genome. We also discuss how the TAC subunits are imported into the mitochondrion and how they assemble to form a new TAC. Finally, we present a comparative analysis of the trypanosomal TAC with open and closed mitotic spindles, which reveals conserved concepts between these diverse DNA segregation systems. The tripartite attachment complex (TAC) of the single mitochondrion of trypanosomes allows precise segregation of its single nucleoid mitochondrial genome during cytokinesis. It couples the segregation of the duplicated mitochondrial genome to the segregation of the basal bodies of the flagella. Here, we provide a model of the molecular architecture of the TAC that explains how its eight essential subunits connect the basal body (BB), across the mitochondrial membranes, with the mitochondrial genome. We also discuss how the TAC subunits are imported into the mitochondrion and how they assemble to form a new TAC. Finally, we present a comparative analysis of the trypanosomal TAC with open and closed mitotic spindles, which reveals conserved concepts between these diverse DNA segregation systems. [ABSTRACT FROM AUTHOR]

CENP-A nucleosomes serve as the assembly point for the kinetochores, which bind chromatin to the spindle apparatus during cell division. Human constitutive centromere-associated network (CCAN) is a 16-protein complex and is the first protein layer of the kinetochore. Only two CCAN proteins, CENP-C and CENP-N, contact the CENP-A nucleosome. Their mode of recognizing the CENP-A nucleosome has been characterized over the past decade. Three human CCAN structures have been published in the past year; slightly earlier, another model was also published for yeast. All structures point to a Y-shaped clamp that can adhere to linear and exposed DNA but not to curved and nucleosome-protected DNA. This conflicts with what we know about CENP-N's recognition of the CENP-A nucleosome. One way to reconcile these conflicting findings is via an intermediary nucleosome remodeling step between the initial recognition of the CENP-A nucleosome by CENP-C and CENP-N, and the final assembly of the remaining CCAN components that constitute the clamp. CENP-A is an essential histone variant that replaces the canonical H3 at the centromeres and marks these regions epigenetically. The CENP-A nucleosome is the specific building block of centromeric chromatin, and it is recognized by CENP-C and CENP-N, two components of the constitutive centromere-associated network (CCAN), the first protein layer of the kinetochore. Recent proposals of the yeast and human (h)CCAN structures position the assembly on exposed DNA, suggesting an elusive spatiotemporal recognition. We summarize the data on the structural organization of the CENP-A nucleosome and the binding of CENP-C and CENP-N. The latter posits an apparent contradiction in engaging the CENP-A nucleosome versus the CCAN. We propose a reconciliatory model for the assembly of CCAN on centromeric chromatin. [ABSTRACT FROM AUTHOR]

To investigate the fate and underlying mechanisms of G2 phase arrest in cancer cells elicited by ionizing radiation (IR). Human melanoma A375 and 92-1 cells were treated with X-rays radiation or Aurora A inhibitor MLN8237 (MLN) and/or p21 depletion by small interfering RNA (siRNA). Cell cycle distribution was determined using flow cytometry and a fluorescent ubiquitin-based cell cycle indicator (FUCCI) system combined with histone H3 phosphorylation at Ser10 (pS10 H3) detection. Senescence was assessed using senescence-associated-β-galactosidase (SA-β-Gal), Ki67, and γH2AX staining. Protein expression levels were determined using western blotting. Tumor cells suffered severe DNA damage and underwent G2 arrest after IR treatment. The damaged cells did not successfully enter M phase nor were they stably blocked at G2 phase but underwent mitotic skipping and entered G1 phase as tetraploid cells, ultimately leading to senescence in G1. During this process, the p53/p21 pathway is hyperactivated. Accompanying p21 accumulation, Aurora A kinase levels declined sharply. MLN treatment confirmed that Aurora A kinase activity is essential for mitosis skipping and senescence induction. Persistent p21 activation during IR-induced G2 phase blockade drives Aurora A kinase degradation, leading to senescence via mitotic skipping. [ABSTRACT FROM AUTHOR]

Global mass spectrometry-based phosphoproteomic analyses have revealed preferences of phosphoprotein phosphatases (PPPs) for distinct phosphorylation site consensus motifs. Phosphoacceptor and phosphorylation site preferences determine dephosphorylation kinetics and provide temporal control of signaling events. Identification of a growing number of PPP holoenzyme-specific short linear motifs (SLiMs) has revealed specific PPP–substrate/scaffold interactions. SLiM-containing proteins are direct PPP substrates or function as scaffolds for indirect substrate recruitment. Phosphorylation site preferences, SLiM affinity, and distance between the phosphorylation site and SLiM combinatorially contribute to the dephosphorylation kinetics. Recent studies demonstrated PPP phosphorylation site preferences and modulation of SLiM affinity in biological contexts, specifically mitosis. Dynamic protein phosphorylation and dephosphorylation are essential regulatory mechanisms that ensure proper cellular signaling and biological functions. Deregulation of either reaction has been implicated in several human diseases. Here, we focus on the mechanisms that govern the specificity of the dephosphorylation reaction. Most cellular serine/threonine dephosphorylation is catalyzed by 13 highly conserved phosphoprotein phosphatase (PPP) catalytic subunits, which form hundreds of holoenzymes by binding to regulatory and scaffolding subunits. PPP holoenzymes recognize phosphorylation site consensus motifs and interact with short linear motifs (SLiMs) or structural elements distal to the phosphorylation site. We review recent advances in understanding the mechanisms of PPP site-specific dephosphorylation preference and substrate recruitment and highlight examples of their interplay in the regulation of cell division. [ABSTRACT FROM AUTHOR]

Sentinel lymph node biopsy is a crucial step in the management of patients affected by melanoma. The decision whether to perform it or not is based on different histological parameters, but the mitotic rate is no longer considered a prognostic variable after the release of the 8th edition of the American Joint Committee on Cancer (AJCC) guidelines. Our objective was to investigate the risk factors that increase the chance for sentinel lymph node positivity in melanomas with a Breslow thickness of less than 2.00 mm, including the mitotic count. A retrospective single-center study was performed on a homogenous cohort of 408 patients treated for cutaneous melanoma. Histological and clinical features were gathered and correlated with the increased risk for sentinel lymph node positivity by means of univariate and multivariate analyses. A statistically significant correlation between a high mitotic index and a positive sentinel lymph node was found in pT1 and pT2 patients, suggesting that in the case of pT1a melanoma with a high number of mitoses, a discussion about whether a sentinel lymph node biopsy is required should be done. [ABSTRACT FROM AUTHOR]

Mitotic kinetochores are initially captured by dynamic microtubules via a "search-and-capture" mechanism. The microtubule motor, dynein, is critical for kinetochore capture as it has been shown to transport microtubule-attached chromosomes toward the spindle pole during prometaphase. The microtubule-binding nuclear division cycle 80 (Ndc80) complex that is recruited to kinetochores in prophase is known to play a central role in forming kinetochore-microtubule (kMT) attachments in metaphase. It is not yet clear, however, how Ndc80 contributes to initial kMT capture during prometaphase. Here, by combining CRISPR/Cas9-mediated knockout and RNAi technology with assays specific to study kMT capture, we show that mitotic cells lacking Ndc80 exhibit substantial defects in this function during prometaphase. Rescue experiments show that Ndc80 mutants deficient in microtubule-binding are unable to execute proper kMT capture. While cells inhibited of dynein alone are predominantly able to make initial kMT attachments, cells co-depleted of Ndc80 and dynein show severe defects in kMT capture. Further, we use an in vitro total internal reflection fluorescence microscopy assay to reconstitute microtubule capture events, which suggest that Ndc80 and dynein coordinate with each other for microtubule plus-end capture and that the phosphorylation status of Ndc80 is critical for productive kMT capture. A novel interaction between Ndc80 and dynein that we identify in prometaphase extracts might be critical for efficient plus-end capture. Thus, our studies, for the first time, identify a distinct event in the formation of initial kMT attachments, which is directly mediated by Ndc80 and in coordination with dynein is required for efficient kMT capture and chromosome alignment. [ABSTRACT FROM AUTHOR]

Direct cleavage, a type of abnormal cleavage in which one zygote divides into three or more blastomeres, has been reported in mammals. The incidence of direct cleavage increases in zygotes with three or more pronuclei (multi-PN) and those showing abnormal pronuclei migration. However, there are few reports on the relationship between pronuclei and direct cleavage, and the effects of these relationships on subsequent embryogenesis have not been clarified. It is difficult to observe pronuclei under visible light, especially in bovine zygotes, because of abundant dark lipid droplets in the cytoplasm. We visualized pronuclei by removing lipid droplets from bovine zygotes and analyzed the relationship between the number of pronuclei and direct cleavage using time-lapse cinematography. The direct cleavage rate of multi-PN zygotes was 78.6%, which was significantly higher than that of zygotes with one pronucleus (1 PN, 0.0%) and two pronuclei (2 PN, 8.2%). Observation of pronuclei migration in 2 PN zygotes showed that 3.1% of 2 PN zygotes had non-apposed pronuclei. The direct cleavage rate of zygotes with non-apposed pronuclei was 66.7%, which was significantly higher than that of zygotes with apposed pronuclei (6.4%). Among multi-PN zygotes, the proportions of zygotes with apposed pronuclei and non-apposed pronuclei were 37.5% and 64.3%, respectively. The direct cleavage rate of multi-PN zygotes with non-apposed pronuclei was 100.0%, which was significantly higher than that of zygotes with apposed pronuclei (40.0%). Three-dimensional live-cell imaging of bovine zygotes injected with the mRNA-encoding histone H2B-mCherry showed that the direct cleavage rates of 2 PN and multi-PN zygotes bypassing syngamy were 63.2% and 75.5%, respectively. These rates were significantly higher than that of 2 PN and multi-PN zygotes that underwent syngamy (5.6% and 20.0%, respectively). Regardless of the number of pronuclei, a high frequency of direct cleavage was observed in zygotes in which the pronuclei did not migrate inward the cytoplasm and bypassed syngamy. These results suggest that abnormal fertilization such as multi-PN and migration error of pronuclei in cattle is the primary reason for direct cleavage during the first mitosis. Assessment of direct cleavage during the first mitosis allows exclusion of embryos with abnormal fertilization and may contribute to in vitro produced embryo transfer success. [ABSTRACT FROM AUTHOR]

It has been generally accepted that the number of oocyte pool in mammalian ovaries is limited and irreversibly consumed throughout the adulthood until menopause, which has been challenged by the existence of female germline stem cells (FGSCs) and their differentiation potentials into oocytes through mitosis. However, there have been a few reports about the existence of porcine FGSCs (pFGSCs) in the neonatal piglet ovarian tissues. In this study, the pFGSCs were isolated from the one day post partum (1 dpp) piglet ovaries by a differential anchoring velocity method combined with the magnetic cell sorting (MACS) using VASA antibody. The gene expression levels and in vitro differentiation potentials of pFGSCs were subsequently analyzed. The results showed that O ct4, C-kit, Vasa, Stella, Ifitm3 and Dazl were expressed in the pFGSCs. A small portion of pFGSCs (2.81 ± 0.76%) spontaneously differentiated into oocyte-like cells (OLCs) with a mean diameter of 50 μm and gene expressions of Vasa, Ifitm3, Blimp1, Gdf9, Zp3, Dazl and Stella. Compared with that of the spontaneous differentiation system, the differentiation rates of pFGSCs into OLCs were significantly increased after the co-supplementations of porcine follicular fluid (PFF) and retinoic acid (RA). Taken together, these above results revealed the direct evidences for the existence of pFGSCs in 1 dpp piglet ovaries and the in vitro differentiation potential of pFGSCs into OLCs, benefiting future research related to the in vitro establishment of livestock FGSCs and the in vitro differentiation of pFGSCs. • FGSCs were isolated from neonatal porcine ovary by differential anchoring velocity and magnetic cell sorting. • Co-supplementations of porcine follicular fluid and retinoic acid benefited the differentiation of pFGSCs into OLCs. • Different methylation modification patterns were found between the OLCs and GV oocytes. [ABSTRACT FROM AUTHOR]

Allelopathy presents significant potential in sustainable agriculture as a defensive mechanism for plants. Hemp (Cannabis sativa L.) exhibited allelopathic properties, and the cultivation of hemp as an economic crop yields substantial leaf residue. This study aims to evaluate the allelopathic effects as well as a mode of action of hemp leaf on target plants and to identify the allelochemicals released from hemp leaf. The investigation focused on the phytotoxic effects of hemp leaf leachate, obtained via the sandwich method at concentrations of 0.25 %, 0.50 % and 1.00 %, on wheat, itchgrass, lettuce, pea bean and hemp species. Results indicated that a high concentration of hemp leaf inhibited seed germination and seedling growth across the tested plants with varying degrees of inhibition observed among recipient species. Analysis of hemp leaf's allelopathic action revealed its efficacy in inducing reactive oxygen species (ROS) overproduction, diminishing cell viability and inhibiting mitosis division, leading to root growth inhibition. These effects are attributed to the synergistic action of phenolic compounds and cannabinoids released from hemp leaves. Pot culture experiments incorporating hemp leaf into soil corroborate observations made under laboratory conditions, demonstrating consistent impacts on germination and seedling growth. Hemp leaf had no effect on pigment accumulation, but at high concentrations, it reduced the leaf area of all tested plants. Hemp leaf residues became intricately intertwined with soil factors. The biomass of hemp leaf emerges as a potential source of herbicidal substances, offering a promising prospect for integration into agricultural systems to achieve effective and sustainable weed control. [Display omitted] • Hemp leaf residue exhibited allelopathic property. • High concentration of hemp leaf inhibited germination and plant growth. • Mode of action of hemp leaf was mitosis inhibition, cell death and ROS induction. • Allelochemicals form hemp leaf was phenolic compounds and cannabinoids. [ABSTRACT FROM AUTHOR]

In actively dividing eukaryotic cells, the nuclear envelope membrane (NEM) expands during the cell cycle to accommodate increases in nuclear volume and formation of two nuclei as a cell passes through mitosis to form daughter cells. NEM expansion is driven by glycerophospholipid (GPL) synthesis that is regulated by the lipin family of phosphatidic acid phosphatases (PAPs). How, and when during the cell cycle, PAPs regulate membrane expansion differs between organisms undergoing a closed or open mitosis. Here, we discuss recent studies that shed light on the mechanisms of NE expansion. Moreover, we examine evidence that NEM expansion not only employs GPLs synthesized in the ER but also lipids whose synthesis is regulated by events at the inner nuclear membrane. [ABSTRACT FROM AUTHOR]

Proteins localized in the inner nuclear membrane (INM) engage in various fundamental cellular processes via their interactions with outer nuclear membrane (ONM) proteins and nuclear lamina. LAP2-emerin-MAN1 domain (LEMD) family proteins, predominantly positioned in the INM, participate in the maintenance of INM functions, including the reconstruction of the nuclear envelope during mitosis, mechanotransduction, and gene transcriptional modulation. Malfunction of LEMD proteins leads to severe tissue-restricted diseases, which may manifest as fatal deformities and defects. In this review, we summarize the significant roles of LEMD proteins in cellular processes, explains the mechanisms of LEMD protein-related diseases, and puts forward questions in less-explored areas like details in tissue-restricted phenotypes. It intends to sort out previous works about LEMD proteins and pave way for future researchers who might discover deeper mechanisms of and better treatment strategies for LEMD protein-related diseases. LEMD proteins and their roles in cellular processes. (A) Domain structures and localization of LEMD proteins. (B) During mitosis, LEMD proteins dispersal and reassembly are caused by BAF phosphorylation and dephosphorylation respectively (up). ANKLE1 accumulates at the midbody with the help of AIR-2/Aurora B kinase and phosphorylation at S192 and S194 to separate sister chromatids (down). (C) When mechanical stresses are applied to nuclear envelope, emerin is phosphorylated and exhibits increased oligomerization and faster diffusion, and phosphorylated emerin competes with SUN for interaction with lamin A/C. Emerin also regulate MKL1/SRF target genes, many of which are cytoskeletal genes (up). ESCRT is recruited to the NER site with the help of BAF and LEMD2 during the repair process (down). (D) LAP2β mediates chromatin localization to nuclear periphery via the interaction with cKrox, HDAC3, and LASs, it also interacts with HDAC3 and regulates its histone 4 deacetylation activity (up). LEMD proteins regulate gene expression via the regulation of transcriptional factors and the participation in signalling pathways (down). LEM, LAP2-emerin-MAN1; LEM-like, LAP2-emerin-MAN1-like; TM, transmembrane; MSC, MAN1-Src1p C-terminal; UHM, U2AF homology motif; ONM, outer nuclear membrane; INM, inner nuclear membrane; ER, endoplasmic reticulum; BAF, barrier-to-autointegration factor; VRK, vaccinia-related kinase; PP2A-B55, protein phosphatase 2A with its B55 regulatory subunit; SUN, Sad/UNC-84; MKL1, myocardin-like protein 1; SRF, serum response factor; NER, nuclear envelope rupture; ESCRT, endosomal sorting complexes required for transport; LAD, lamina-associating domain; LAS, lamina-associating sequence, Ac, acetyl group; cKrox, the vertebrate ortholog of the Drosophila GAGA factor; HDAC3, histone deacetylase 3. [Display omitted] [ABSTRACT FROM AUTHOR]

The Cell Division Cycle Associated 2 (CDCA2) gene is responsible for encoding a targeting subunit of cell-cycle associated protein. CDCA2 plays a crucial role in various cellular processes, including chromosome segregation and decondensation, nuclear envelope reassembly, microtubule assembly, and DNA damage response. Additionally, CDCA2 is involved in multiple signaling pathways such as the PI3K/Akt pathway and p53 pathway. Undoubtedly, there exists a strong association between CDCA2 and cancer. Numerous studies have reported that elevated levels of CDCA2 are correlated with poor prognosis and several clinicopathological characteristics like tumor size and TNM stage across different types of cancer. Therefore, CDCA2 holds great potential as both a biomarker for diagnosis and a therapeutic target for interventions such as targeted therapies or immunotherapy. Given its promising prospects in scientific research and clinical applications, it is imperative for researchers to delve into the underlying mechanisms of CDCA2 and explore its utilization. • An insight into the basic mechanism for the role of CDCA2 in the cell division process. • Adetailed summary of the complex relationship between CDCA2 and tumor progression. • Feasible ideas to further investigate the oncogeneCDCA2. • Potential strategies to translate the theory of CDCA2 into practical clinical interventions. [ABSTRACT FROM AUTHOR]

The nuclear envelope (NE) is central to the architecture of eukaryotic cells, both as a physical barrier separating the nucleus from the cytoplasm and as gatekeeper of selective transport between them. However, in open mitosis, the NE fragments to allow for spindle formation and segregation of chromosomes, resulting in intermixing of nuclear and cytoplasmic soluble fractions. Recent studies have shed new light on the mechanisms driving reinstatement of soluble proteome homeostasis following NE reformation in daughter cells. Here, we provide an overview of how mitotic cells confront this challenge to ensure continuity of basic cellular functions across generations and elaborate on the implications for the proteasome – a macromolecular machine that functions in both cytoplasmic and nuclear compartments. How dividing cells reinstate protein homeostasis following intermixing of nuclear and cytosolic components in open mitosis is a critical aspect of cell biology. Nuclear exclusion of (large) cytosolic proteins during late mitosis is the result of physical constraints on the genome that include chromatin condensation (alongside with swelling of the nuclear envelope (NE) formed around the decondensing chromatin) and chromosome clustering, both of which prevent aberrant inclusion of cytosolic molecules inside newly formed nuclei. After nuclear exclusion in late mitosis, nuclear protein complexes such as proteasomes, are swiftly reimported into the newly formed nucleus. Nuclear import of the proteasome is facilitated by AKIRIN2 and the NE transport machinery. Targeting protein homeostasis during mitosis could be a promising target for therapy. [ABSTRACT FROM AUTHOR]

Cartwheel assembly is considered the first step in the initiation of procentriole biogenesis; however, the reason for persistence of the assembled human cartwheel structure from S phase to late mitosis remains unclear. Here, we demonstrate mainly using cell synchronization, RNA interference, immu-nofluorescence and time-lapse-microscopy, biochemical anal-ysis, and methods that the cartwheel persistently assembles and maintains centriole engagement and centrosome integrity during S phase to late G2 phase. Blockade of the continuous accumulation of centriolar Sas-6, a major cartwheel protein, after procentriole formation induces premature centriole disengagement and disrupts pericentriolar matrix integrity. Additionally, we determined that during mitosis, CDK1-cyclin B phosphorylates Sas-6 at T495 and S510, disrupting its binding to cartwheel component STIL and pericentriolar component Nedd1 and promoting cartwheel disassembly and centriole disengagement. Perturbation of this phosphorylation maintains the accumulation of centriolar Sas-6 and retains centriole engagement during mitotic exit, which results in the inhibition of centriole reduplication. Collectively, these data demonstrate that persistent cartwheel assembly after procen- triole formation maintains centriole engagement and that this configuration is relieved through phosphorylation of Sas-6 by CDK1-cyclin B during mitosis in human cells. [ABSTRACT FROM AUTHOR]

Optical tweezers (OT) provide a noninvasive approach for delivering minute physical forces to targeted objects. Controlling such forces in living cells or in vitro preparations allows for the measurement and manipulation of numerous processes relevant to the form and function of cells. As such, OT have made important contributions to our understanding of the structures of proteins and nucleic acids, the interactions that occur between microscopic structures within cells, the choreography of complex processes such as mitosis, and the ways in which cells interact with each other. In this review, we highlight recent contributions made to the field of cell biology using OT and provide basic descriptions of the physics, the methods, and the equipment that made these studies possible. Optical tweezers (OT) can measure or apply minute forces inside cells noninvasively. Recent developments in OT technology have allowed insights into the structure, function, and behavior of cells. Particular progress has been made in understanding mitotic machinery, cellular viscoelasticity, and metastasis. Emerging methods in optical physics promise to extend the breadth and utility of OT in the years to come. [ABSTRACT FROM AUTHOR]

Cell-cycle progression and division are fundamental biological processes in animal cells, and their biochemical regulation has been extensively studied. An emerging body of work has revealed how mechanical interactions of cells with their microenvironment in tissues, including with the extracellular matrix (ECM) and neighboring cells, also plays a crucial role in regulating cell-cycle progression and division. We review recent work on how cells interpret physical cues and alter their mechanics to promote cell-cycle progression and initiate cell division, and then on how dividing cells generate forces on their surrounding microenvironment to successfully divide. Finally, the article ends by discussing how force generation during division potentially contributes to larger tissue-scale processes involved in development and homeostasis. Tissue-level tension, cytoskeletal tension, and stiff substrates for 2D culture generally promote cell-cycle progression and division, whereas confining environments or compression inhibit cell growth, leading to delayed or halted cell-cycle progression and division. Cells dividing in confining environments generate extracellular forces to drive major morphological changes which are necessary for proper division completion, including mitotic rounding, division elongation, and postdivision spreading. Extracellular forces generated during cell division contribute to cell migration and tissue-scale processes important in development, including tissue growth, invagination, luminogenesis, and epithelial stratification. Cancer cells are able to undergo cell-cycle progression and cell division within the confining tumor microenvironment. [ABSTRACT FROM AUTHOR]

Glioblastoma (GBM) is the most frequent and aggressive primary brain cancer in adult patients. A variety of long non-coding RNAs play an important role in the pathogenesis of GBM, however the molecular functions of most of them still remain elusive. Here, we investigated linc-RoR (long intergenic non-protein coding RNA, regulator of reprogramming) using GBM neurospheres obtained from 12 different patients. We demonstrated that the highest level of this transcript is detected in cells with increased EGFR expression. According to our data, linc-RoR knockdown decreases cell proliferation, increases sensitivity to DNA damage, and downregulates the level of cancer stem cell (CSC) markers. On the other hand, linc-RoR overexpression promote cell growth and increases the proportion of CSCs. Analysis of RNA sequencing data revealed that linc-RoR affects expression of genes involved in the regulation of mitosis. In agreement with this observation, we have showen that the highest level of linc-RoR is detected in the G2/M phase of the cell cycle, when linc-RoR is localized on the chromosomes of dividing cells. Based on our results, we can propose that linc-RoR performs pro-oncogenic functions in human gliobalstoma cells, which may be associated with the regulation of mitotic progression and GBM stemness. • Linc-RoR is upregulated in EGFR positive GBM cells. • Linc-RoR promotes stemness and inhibit apoptosis. • Linc-RoR localizes on the chromosomes during cell division. • Linc-RoR is involved in the regulation of mitosis. [ABSTRACT FROM AUTHOR]

Cell division is tightly regulated and requires an expanded energy supply. However, how this energy is generated remains unclear. Here, we establish a correlation between two mitochondrial Ca2+ influx events and ATP production during mitosis. While both events promote ATP production during mitosis, the second event, the Ca2+ influx surge, is substantial. To facilitate this Ca2+ influx surge, the lamin B receptor (LBR) organizes a mitosis-specific endoplasmic reticulum (ER)-mitochondrial contact site (ERMCS), creating a rapid Ca2+ transport pathway. LBR acts as a tether, connecting the ER Ca2+ release channel IP 3 R with the mitochondrial VDAC2. Depletion of LBR disrupts the Ca2+ influx surge, reduces ATP production, and postpones the metaphase-anaphase transition and subsequent cell division. These findings provide insight into the mechanisms underlying mitotic energy production and supply required for cell proliferation. [Display omitted] • The number of ERMCSs increases in mitosis • Mitotic ERMCS strengthens the Ca2+ uptake capacity of mitotic mitochondria • LBR binds VDAC2 in mitosis, mediating these mitosis-specific ERMCSs • Mitochondrial Ca2+ influx surge promotes the metaphase-anaphase transition Zhao et al. describe a mechanism by which mitochondrial Ca2+ regulates the metaphase-anaphase transition through LBR-mediated mitosis-specific ER-mitochondria contact sites (ERMCSs). The LBR-mediated ERMCSs promote the mitochondrial Ca2+ influx surge, which is essential for expanded energy generation during mitosis. [ABSTRACT FROM AUTHOR]

[Display omitted] Caspase recruitment domain (CARD)-containing protein 14 (CARD14) is an intracellular protein that mediates nuclear factor-kappa B (NF-ĸB) signaling and proinflammatory gene expression in skin keratinocytes. Several hyperactivating CARD14 mutations have been associated with psoriasis and other inflammatory skin diseases. CARD14-induced NF-ĸB signaling is dependent on the formation of a CARD14-BCL10-MALT1 (CBM) signaling complex, but upstream receptors and molecular mechanisms that activate and regulate CARD14 signaling are still largely unclear. Using unbiased affinity purification and mass spectrometry (AP-MS) screening, we discover polo-like kinase 1 (PLK1) as a novel CARD14-binding protein. CARD14-PLK1 binding is independent of the CARD14 CARD domain but involves a consensus phospho-dependent PLK1-binding motif in the CARD14 linker region (LR). Expression of the psoriasis-associated CARD14(E138A) variant in human keratinocytes induces the recruitment of PLK1 to CARD14-containing signalosomes in interphase cells, but does not affect the specific location of PLK1 in mitotic cells. Finally, disruption of the PLK1-binding motif in CARD14(E138A) increases CARD14-induced proinflammatory signaling and gene expression. Together, our data identify PLK1 as a novel CARD14-binding protein and indicate a negative regulatory role for PLK1 in CARD14 signaling. [ABSTRACT FROM AUTHOR]

FOXA1 serves as a crucial pioneer transcription factor during developmental processes and plays a pivotal role as a mitotic bookmarking factor to perpetuate gene expression profiles and maintain cellular identity. During mitosis, the majority of FOXA1 dissociates from specific DNA binding sites and redistributes to non-specific binding sites; however, the regulatory mechanisms governing molecular dynamics and activity of FOXA1 remain elusive. Here, we show that mitotic kinase Aurora B specifies the different DNA binding modes of FOXA1 and guides FOXA1 biomolecular condensation in mitosis. Mechanistically, Aurora B kinase phosphorylates FOXA1 at Serine 221 (S221) to liberate the specific, but not the non-specific, DNA binding. Interestingly, the phosphorylation of S221 attenuates the FOXA1 condensation that requires specific DNA binding. Importantly, perturbation of the dynamic phosphorylation impairs accurate gene reactivation and cell proliferation, suggesting that reversible mitotic protein phosphorylation emerges as a fundamental mechanism for the spatiotemporal control of mitotic bookmarking. [Display omitted] • FOXA1 is phosphorylated at Serine 221 in the DNA binding domain by Aurora B in mitosis • FOXA1 phosphorylation impairs the specific, but not the non-specific, DNA binding • FOXA1 forms specific DNA-dependent condensates, which are disrupted by phosphorylation • Dynamic FOXA1 phosphorylation regulates transcription reactivation and cell proliferation Zhang et al. discovered that bookmarking factor FOXA1 undergoes dynamic phosphorylation at Serine 221 by Aurora B during mitosis, orchestrating its different DNA binding patterns and the periodic FOXA1 condensate formation during the cell cycle. Moreover, this phosphorylation regulates the target gene reactivation post-mitosis and cancer cell proliferation. [ABSTRACT FROM AUTHOR]

The forces that orient the spindle in human cells remain poorly understood due to a lack of direct mechanical measurements in mammalian systems. We use magnetic tweezers to measure the force on human mitotic spindles. Combining the spindle's measured resistance to rotation, the speed at which it rotates after laser ablating astral microtubules, and estimates of the number of ablated microtubules reveals that each microtubule contacting the cell cortex is subject to ∼5 pN of pulling force, suggesting that each is pulled on by an individual dynein motor. We find that the concentration of dynein at the cell cortex and extent of dynein clustering are key determinants of the spindle's resistance to rotation, with little contribution from cytoplasmic viscosity, which we explain using a biophysically based mathematical model. This work reveals how pulling forces on astral microtubules determine the mechanics of spindle orientation and demonstrates the central role of cortical dynein clustering. [Display omitted] • Cytoplasmic viscosity does not determine the spindle's resistance to rotation • Each astral microtubule contacting the cell cortex is pulled on by one dynein motor • Pulling forces on astral microtubules determine spindle orientation mechanics • Dynein motor clustering at the cell cortex controls spindle orientation mechanics The orientation of the mitotic spindle within the cell sets the division axis, which is a crucial aspect of tissue development. Anjur-Dietrich et al. show that the mechanics of spindle orientation is determined by clustering of dynein motors at the cell cortex, which exert pulling forces on astral microtubules. [ABSTRACT FROM AUTHOR]

The Eyes Absent family (EYA1–4) are a group of dual function proteins that act as both tyrosine phosphatases and transcriptional co-activators. EYA proteins play a vital role in development, but are also aberrantly overexpressed in cancers, where they often confer an oncogenic effect. Precisely how the EYAs impact cell biology is of growing interest, fuelled by the therapeutic potential of an expanding repertoire of EYA inhibitors. Recent functional studies suggest that the EYAs are important players in the regulation of genome maintenance pathways including DNA repair, mitosis, and DNA replication. While the characterized molecular mechanisms have predominantly been ascribed to EYA phosphatase activities, EYA co-transcriptional activity has also been found to impact the expression of genes that support these pathways. This indicates functional convergence of EYA phosphatase and co-transcriptional activities, highlighting the emerging importance of the EYA protein family at the intersection of genome maintenance mechanisms. In this review, we discuss recent progress in defining EYA protein substrates and transcriptional effects, specifically in the context of genome maintenance. We then outline future directions relevant to the field and discuss the clinical utility of EYA inhibitors. • EYA1–4 are dual function proteins with converging roles in genome maintenance. • The EYAs act as tyrosine phosphatases and can dephosphorylate H2AX, RAD51 and PLK1. • The EYAs also function as co-transcriptional activators of genes involved in genome maintenance. • EYA phosphatase and co-transcriptional inhibitors have emerging potential as cancer therapeutics. [ABSTRACT FROM AUTHOR]

Loss of Heterozygosity (LOH) due to mitotic recombination is frequently associated with the development of various cancers (e.g. retinoblastoma). LOH is also an important source of genetic diversity, especially in organisms where meiosis is infrequent. Irc20 is a putative helicase, and E3 ubiquitin ligase involved in DNA double-strand break repair pathway. We analyzed genome-wide LOH events, gross chromosomal changes, small insertion-deletions and single nucleotide mutations in eleven S. cerevisiae mutation accumulation lines of irc20∆ , which underwent 50 mitotic bottlenecks. LOH enhancement in irc20∆ was small (1.6 fold), but statistically significant as compared to the wild type. Short (≤ 1 kb) and long (> 10 kb) LOH tracts were significantly enhanced in irc20∆. Both interstitial and terminal LOH events were also significantly enhanced in irc20∆ compared to the wild type. LOH events in irc20∆ were more telomere proximal and away from centromeres compared to the wild type. Gross chromosomal changes, single nucleotide mutations and in-dels were comparable between irc20∆ and wild type. Locus based and genome-wide analysis of meiotic recombination showed that meiotic crossover frequencies are not altered in irc20∆. These results suggest Irc20 primarily regulates mitotic recombination and does not affect meiotic crossovers. Our results suggest that the IRC20 gene is important for regulating LOH frequency and distribution. • Loss of heterozygosity (LOH) is enhanced in irc20∆ mutant. • Short (≤ 1 kb) and long (> 10 kb) tract LOH events are enhanced in irc20∆. • Gross chromosomal changes, base mutations and in-dels are not enhanced in irc20∆. • Irc20 is expressed in meiosis but does not affect meiotic crossovers. • Irc20 is important for regulating the frequency and distribution of LOH events. [ABSTRACT FROM AUTHOR]

Piwi proteins and Piwi interacting RNAs, piRNAs, presented in germline cells play a role in transposon silencing during germline development. In contrast, the role of somatic Piwi proteins and piRNAs still remains obscure. Here, we characterize the expression pattern and distribution of piRNAs in human renal cells in terms of their potential role in kidney development. Further, we show that all PIWI genes are expressed at the RNA level, however, only PIWIL1 gene is detected at the protein level by western blotting in healthy and cancerous renal cells. So far, the expression of human Piwil1 protein has only been shown in testes and cancer cells, but not in healthy somatic cell lines. Since we observe only Piwil1 protein, the regulation of other PIWI genes is probably more intricated, and depends on environmental conditions. Next, we demonstrate that downregulation of Piwil1 protein results in a decrease in the rate of cell proliferation, while no change in the level of apoptotic cells is observed. Confocal microscopy analysis reveals that Piwil1 protein is located in both cellular compartments, cytoplasm and nucleus in renal cells. Interestingly, in nucleus region Piwil1 is observed close to the spindle during all phases of mitosis in all tested cell lines. It strongly indicates that Piwil1 protein plays an essential role in proliferation of somatic cells. Moreover, involvement of Piwil1 in cell division could, at least partly, explain invasion and metastasis of many types of cancer cells with upregulation of PIWIL1 gene expression. It also makes Piwil1 protein as a potential target in the anticancer therapy. • Stem cell and cancer cell lines exhibit a convergent profile of RNA fragment reads corresponding to the length of piRNA. • The largest set of transcripts mapping to piRNA is common for all cell lines which proves the conserved function of piRNAs. • Piwil1 protein has been shown for the first time to be detected by western blot in non-cancerous somatic renal cell lines. • Downregulation of Piwil1 leads to changes in the proliferation rate of renal cells, but it does not trigger apoptosis. • Piwil1 is involved in the division of kidney cells. [ABSTRACT FROM AUTHOR]

Mechanistic Target of Rapamycin Complex 1 (mTORC1) is a master metabolic regulator that is active in nearly all proliferating eukaryotic cells; however, it is unclear whether mTORC1 activity changes throughout the cell cycle. We find that mTORC1 activity oscillates from lowest in mitosis/G1 to highest in S/G2. The interphase oscillation is mediated through the TSC complex but is independent of major known regulatory inputs, including Akt and Mek/Erk signaling. By contrast, suppression of mTORC1 activity in mitosis does not require the TSC complex. mTORC1 has long been known to promote progression through G1. We find that mTORC1 also promotes progression through S and G2 and is important for satisfying the Chk1/Wee1-dependent G2/M checkpoint to allow entry into mitosis. We also find that low mTORC1 activity in G1 sensitizes cells to autophagy induction in response to partial mTORC1 inhibition or reduced nutrient levels. Together, these findings demonstrate that mTORC1 is differentially regulated throughout the cell cycle, with important phase-specific consequences for proliferating cells. [Display omitted] • mTORC1 activity oscillates throughout the cell cycle, peaking in S/G2 and low in M/G1 • The interphase oscillation in mTORC1 activity is mediated through the TSC complex • mTORC1 promotes progression through G1, S, and G2 but not mitosis • Low mTORC1 activity in G1 sensitizes cells to induction of autophagy mTORC1 is a master metabolic regulator that stimulates anabolic cell growth and proliferation and suppresses catabolic processes such as autophagy. Joshi et al. find that mTORC1 activity oscillates throughout the cell cycle, promoting progression through interphase and entry into mitosis and resulting in differential sensitivity to autophagy induction. [ABSTRACT FROM AUTHOR]

Ubiquitination is an essential regulator of cell division. The kinase Polo-like kinase 1 (PLK1) promotes protein degradation at G2/M phase through the E3 ubiquitin ligase Skp1-Cul1-F box (SCF)βTrCP. However, the magnitude to which PLK1 shapes the mitotic proteome is uncharacterized. Combining quantitative proteomics with pharmacologic PLK1 inhibition revealed a widespread, PLK1-dependent program of protein breakdown at G2/M. We validated many PLK1-regulated proteins, including substrates of the cell-cycle E3 SCFCyclin F, demonstrating that PLK1 promotes proteolysis through at least two distinct E3 ligases. We show that the protein-kinase-A-anchoring protein A-kinase anchor protein 2 (AKAP2) is cell-cycle regulated and that its mitotic degradation is dependent on the PLK1/βTrCP signaling axis. Expression of a non-degradable AKAP2 mutant resulted in actin defects and aberrant mitotic spindles, suggesting that AKAP2 degradation coordinates cytoskeletal organization during mitosis. These findings uncover PLK1's far-reaching role in shaping the mitotic proteome post-translationally and have potential implications in malignancies where PLK1 is upregulated. [Display omitted] • PLK1 promotes a widespread program of protein degradation at G2/M phase of the cell cycle • PLK1-mediated degradation is coordinated through at least two SCF-family E3 ligases • AKAP2, a PKA-anchoring protein, is regulated by the PLK1/βTrCP signaling axis • AKAP2 degradation coordinates cytoskeletal dynamics in mitosis Mouery et al. utilize deep, quantitative proteomics to reveal a PLK1-regulated program of G2/M protein degradation. They show that the PKA-anchoring protein AKAP2 is degraded in a manner dependent on PLK1 and the E3 ubiquitin ligase SCFβTrCP and that disruption of AKAP2 degradation results in defects of the mitotic cytoskeleton. [ABSTRACT FROM AUTHOR]

Benzimidazole 1 (BUB1) and budding uninhibited by benzimidazole 1-related 1 (BUBR1) are multidomain paralogs with key roles in chromosome alignment during mitosis and the spindle assembly checkpoint (SAC), an evolutionarily conserved signaling pathway that monitors errors in chromosome segregation during cell division in eukaryotes. Although BUB1 and BUBR1 share a similar domain organization and short linear interaction motifs (SLiMs), they control distinct aspects of chromosome congression and the SAC. Here we discuss the roles of BUB1 and BUBR1 SLiMs in mitosis and complement this with additional insights gleamed from studying their evolution. We show that BUB1 and BUBR1 SLiMs form highly specific interactions that are carefully orchestrated in space and time and contend that they define BUB1 and BUBR1 as organizing hubs that drive SAC signaling and ensure genome stability. Budding uninhibited by benzimidazole 1 (BUB1) and budding uninhibited by benzimidazole 1-related 1 (BUBR1) act as a hub of protein–protein interactions at the kinetochore. They harbor short linear interaction motifs (SLiMs) that confer them unique functionalities in the spindle assembly checkpoint (SAC). These SLiMs are highly conserved during evolution, but with some important deviations that are species specific. Although the functions of subcellular pools of BUB1 and BUBR1 remain to be fully understood, they are likely to control the flow of information in SAC signaling. The molecular description of BUB1 and BUBR1 roles in the SAC signaling is essential to enhance our understanding of the mechanisms that govern cell division in health and disease conditions. This knowledge will inform of the defects in the process of cell division control that are associated with aberrant chromosome segregation and genome instability. In this context, the possibility of interfering with mitosis progression in tumor cells by affecting specific protein–protein interactions that are dependent on BUB1 and/or BUBR1 may represent a new therapeutic window for the treatment of cancer. [ABSTRACT FROM AUTHOR]

• Using and impact of nanoparticles in agriculture. • Genotoxicity of nanoparticles in plant. • Effect of commercial amino zinc nanoparticles on cell division. • The harmful effect of commercial amino zinc nanoparticles in chromosomal structure. Nanoparticles have a positive impact in several subjects especially in agriculture, while their safety is still being debated. Numerous commercial nano pesticide, insecticides, and fertilizers products are found in the local markets without any intensely studies on the side effect of these products on plant, human as well as environmental effects. The present study aimed to evaluate the genotoxicity of commercial amino zinc nanoparticles (AZ NPs) on Triticum aestivum L. during seeds germination and root elongation using concentration ranges (50, 100, and 150 ppm) at different exposure times (8, 16 and 24 hrs). Long term exposure to AZ NPs, exhibited only slight variation in germination rates and the elongation of roots was affected by AZ NPs treatment ranged from 97.66 to 100%. Significant reduction in the mitotic index was 35.33% after 24 hrs and 150 ppm of AZ NPs, was also observed comparing with control which was 88.0%. Genotoxicity was evaluated at a cytological level in root meristems that revealed sever variations in mitotic activity, chromosomal aberrations, and micronuclei release. Results exhibited that nano amino zinc could enter effortlessly into the cells and inhibit the normal cellular function. The decrease in the emergence of chromosomal aberrations resulting from AZ NPs exposure in a dose-dependent manner was clearly indicated that AZ NPs has induced genotoxic effect on wheat root tips. [ABSTRACT FROM AUTHOR]

Both the DNA damage response (DDR) and the mitotic checkpoint are critical for the maintenance of genomic stability. Among proteins involved in these processes, the ataxia-telangiectasia mutated (ATM) kinase is required for both activation of the DDR and the spindle assembly checkpoint (SAC). In mitosis without DNA damage, the enzymatic activity of ATM is enhanced; however, substrates of ATM in mitosis are unknown. Using stable isotope labeling of amino acids in cell culture mass spectrometry analysis, we identified a number of proteins that can potentially be phosphorylated by ATM during mitosis. This list is highly enriched in proteins involved in cell cycle regulation and the DDR. Among them, we further validated that ATM phosphorylated budding uninhibited by benzimidazoles 3 (Bub3), a major component of the SAC, on serine 135 (Ser135) both in vitro and in vivo. During mitosis, this phosphorylation promoted activation of another SAC component, benzimidazoles 1. Mutation of Bub3 Ser135 to alanine led to a defect in SAC activation. Furthermore, we found that ATMmediated phosphorylation of Bub3 on Ser135 was also induced by ionizing radiation-induced DNA damage. However, this event resulted in independent signaling involving interaction with the Ku70-Ku80-DNA-PKcs sensor/kinase complex, leading to efficient nonhomologous end-joining repair. Taken together, we highlight the functional significance of the crosstalk between the kinetochore-oriented signal and double-strand break repair pathways via ATM phosphorylation of Bub3 on Ser135. [ABSTRACT FROM AUTHOR]

Carboxy-terminal domain (CTD) small phosphatase like 2 (CTDSPL2), also known as SCP4 or HSPC129, is a new member of the small CTD phosphatase (SCP) family and its role in cancers remains unclear. Here, we used a Phos-tag technique to screen a series of phosphatases and identified CTDSPL2 as a mitotic regulator. We demonstrated that CTDSPL2 was phosphorylated at T86, S104, and S134 by cyclin-dependent kinase 1 (CDK1) in mitosis. Depletion of CTDSPL2 led to mitotic defects and prolonged mitosis. Resultantly, CTDSPL2 deletion restrained proliferation, migration, and invasion in pancreatic cancer cells. We further confirmed the dominant negative effects of a phosphorylation-deficient mutant form of CTDSPL2, implying the biological significance of CTDSPL2 mitotic phosphorylation. Moreover, RT2 cell cycle array analysis revealed p21 and p27 as downstream regulators of CTDSPL2, and inhibition of p21 and/or p27 partially rescued the phenotype in CTDSPL2-deficient cell lines. Importantly, both CTDSPL2 depletion and phosphorylation-deficient mutant CTDSPL2 hindered tumor growth in xenograft models. Together, our findings for the first time highlight the novel role of CTDSPL2 in regulating cell mitosis, proliferation and motility in pancreatic cancer and point out the implications of CTDSPL2 in regulating two critical cell cycle participants (p21 and p27), providing an alternative molecular target for pancreatic cancer treatment. [ABSTRACT FROM AUTHOR]

The Chromosomal Passenger Complex (CPC) regulates a plethora of processes during multiple stages of nuclear and cytoplasmic division. Early during mitosis, the CPC is recruited to centromeres and kinetochores, and ensures that the duplicated chromosomes become properly connected to microtubules from opposite poles of the mitotic spindle. Progression into anaphase is accompanied by a striking relocation of the CPC from centromeres to the antiparallel microtubule overlaps of the anaphase spindle and to the equatorial cortex. This translocation requires direct interactions of the CPC with the kinesin-6 family member MKLP2/KIF20A, and the inactivation of cyclin B-cyclin-dependent kinase-1 (CDK1). Here, we review recent progress in the regulation of this relocation event. Furthermore, we discuss why the CPC must be relocated during early anaphase in light of recent advances in the functions of the CPC post metaphase. A key feature of the CPC is that it changes location during early anaphase, from the centromeric region of the chromosomes to the anaphase spindle midzone and the equatorial cell cortex. Relocation requires the inactivation of cyclin B-CDK1 and the subsequent dephosphorylation of INCENP and MKLP2/KIF20A, to promote CPC-MKLP2 complex formation and to stimulate ATPase activity of MKLP2. At the spindle midzone and equatorial cortex, the CPC promotes anaphase spindle remodeling and the initiation of cytokinesis. Spindle midzone-localized CPC is proposed to support the timely resolution of lagging chromosomes during anaphase. [ABSTRACT FROM AUTHOR]

Kinetochores are the macromolecular protein complexes that govern chromosome movement by binding spindle microtubules during mitosis and meiosis. Centromeres are the specific chromosomal regions that serve as the platform on which kinetochores assemble. Despite their essentiality for proper chromosome segregation, the size and organization of centromeres vary dramatically between species, while different compositions of kinetochores are found among eukaryotes. Here we discuss recent progress in understanding centromeres and kinetochores in non-traditional model eukaryotes. We specifically focus on select lineages (holocentric insects, early diverging fungi, and kinetoplastids) that lack CENP-A, a centromere-specific histone H3 variant that is critical for kinetochore specification and assembly in many eukaryotes. We also highlight some organisms that might have hitherto unknown types of kinetochore proteins. [ABSTRACT FROM AUTHOR]

The Golgi complex is an essential organelle of the eukaryotic exocytic pathway. A subfamily of Golgi matrix proteins, called GRASPs, is central in stress-induced unconventional secretion, Golgi dynamics during mitosis/apoptosis, and Golgi ribbon formation. The Golgi ribbon is vertebrate-specific and correlates with the appearance of two GRASP paralogues and two Golgins (GM130/Golgin45), which form specific GRASP-Golgin pairs. The molecular details of their appearance only in Metazoans are unknown. Moreover, despite new functionalities supported by GRASP paralogy, little is known about their structural and evolutionary differences. Here, we used ancestor sequence reconstruction and biophysical/biochemical approaches to assess the evolution of GRASPs structure/dynamics, fibrillation, and how they started anchoring their Golgin partners. Our data showed that a GRASP ancestor anchored Golgins before gorasp gene duplication in Metazoans. After gene duplication, variations within the GRASP binding pocket determined which paralogue would recruit which Golgin. These interactions are responsible for their specific Golgi location and Golgi ribbon appearance. We also suggest that GRASPs have a long-standing capacity to form supramolecular structures, affecting their participation in stress-induced processes. [ABSTRACT FROM AUTHOR]

Nuclear pore complexes (NPCs) are huge protein assemblies within the nuclear envelope (NE) that serve as selective gates for macromolecular transport between nucleus and cytoplasm. When higher eukaryotic cells prepare for division, they rapidly disintegrate NPCs during NE breakdown such that nuclear and cytoplasmic components mix to enable the formation of a cytoplasmic mitotic spindle. At the end of mitosis, reassembly of NPCs is coordinated with the establishment of the NE around decondensing chromatin. We review recent progress on mitotic NPC disassembly and reassembly, focusing on vertebrate cells. We highlight novel mechanistic insights into how NPCs are rapidly disintegrated into conveniently reusable building blocks, and put divergent models of (post-)mitotic NPC assembly into a spatial and temporal context. NPC disintegration requires the combined activity of multiple mitotic kinases and exploits multisite phosphorylation, linking it to mitotic commitment. NPC disassembly generates smaller building blocks that are conveniently reusable during mitotic exit, and some of these may even remain membrane-associated throughout mitosis and serve as templates for NPC reassembly. Enclosure of all chromatin into a single nucleus that contains transport-competent NPCs requires chromosome clustering and the coordination of NPC assembly and NE reformation. Mitotic NPC reassembly starts at lateral areas of the decondensing chromatin mass, away from spindle microtubules, possibly by attraction of perforated endoplasmic reticulum (ER) membrane sheets to defined NPC assembly sites on chromatin. NPC reassembly during mitotic exit may encompass a range of modes whose prevalence is spatially and temporarily determined. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae is at the forefront of defining the major recombination mechanisms/models that repair targeted double-strand breaks during mitosis. Each of these models predicts specific molecular intermediates as well as genetic outcomes. Recent use of single-nucleotide polymorphisms to track the exchange of sequences in recombination products has provided an unprecedented level of detail about the corresponding intermediates and the extents to which different mechanisms are utilized. This approach also has revealed complexities that are not predicted by canonical models, suggesting that modifications to these models are needed. Current data are consistent with the initiation of most inter-homolog spontaneous mitotic recombination events by a double-strand break. In addition, the sister chromatid is preferred over the homolog as a repair template. [ABSTRACT FROM AUTHOR]

Increased permeability is implicated in the pathogenesis of intestinal disease. In vitro and in vivo studies have linked down-regulation of the scaffolding protein ZO-1, encoded by the TJP1 gene, to increased tight junction permeability. This has not, however, been tested in vivo. Here, we assessed the contributions of ZO-1 to in vivo epithelial barrier function and mucosal homeostasis. Public Gene Expression Omnibus data sets and biopsy specimens from patients with inflammatory bowel disease (IBD) and healthy control individuals were analyzed. Tjp1 f/f ;vil-CreTg mice with intestinal epithelial–specific ZO-1 knockout (ZO-1KO.IEC) mice and Tjp1 f/f mice littermates without Cre expression were studied using chemical and immune-mediated models of disease as well as colonic stem cell cultures. ZO-1 transcript and protein expression were reduced in biopsy specimens from patients with IBD. Despite mildly increased intestinal permeability, ZO-1KO.IEC mice were healthy and did not develop spontaneous disease. ZO-1KO.IEC mice were, however, hypersensitive to mucosal insults and displayed defective repair. Furthermore, ZO-1–deficient colonic epithelia failed to up-regulate proliferation in response to damage in vivo or Wnt signaling in vitro. ZO-1 was associated with centrioles in interphase cells and mitotic spindle poles during division. In the absence of ZO-1, mitotic spindles failed to correctly orient, resulting in mitotic catastrophe and abortive proliferation. ZO-1 is, therefore, critical for up-regulation of epithelial proliferation and successful completion of mitosis. ZO-1 makes critical, tight junction–independent contributions to Wnt signaling and mitotic spindle orientation. As a result, ZO-1 is essential for mucosal repair. We speculate that ZO-1 down-regulation may be one cause of ineffective mucosal healing in patients with IBD. [Display omitted] Down-regulation of the tight junction protein ZO-1 in disease causes only mild increases in tight junction permeability but profoundly impairs mucosal healing. [ABSTRACT FROM AUTHOR]

Delta (δ-) and epsilon (ε-) tubulin are lesser-known cousins of alpha (α-) and beta (β-) tubulin. They are likely to regulate centriole function in a broad range of species; however, their in vivo role and mechanism of action in mammals remain mysterious. In unicellular species and mammalian cell lines, mutations in δ- and ε-tubulin cause centriole destabilization and atypical mitosis and, in the most severe cases, cell death. Beyond the centriole, δ- and ε-tubulin localize to the manchette during murine spermatogenesis and interact with katanin-like 2 (KATNAL2), a protein with microtubule (MT)-severing properties, indicative of novel non-centriolar functions. Herein we summarize the current knowledge surrounding δ- and ε-tubulin, identify pathways for future research, and highlight how and why spermatogenesis and embryogenesis are ideal systems to define δ- and ε-tubulin function in vivo. Delta and epsilon tubulin are required for triplet microtubule stability in centrioles and basal bodies. Mutations in these tubulins result in compromised triplet microtubule structures, wherein the centriole loses its ability to facilitate efficient mitosis and the basal body has a reduced ability to form cilia. Delta and epsilon tubulin can interact with each other and are posited to interact with both alpha/beta tubulin and non-tubulin proteins. Delta and epsilon tubulin have shown localization to non-centriolar structures, indicative of a potential function outside the centriole. [ABSTRACT FROM AUTHOR]

Cytokinesis, the final step of mitosis, is mediated by an actomyosin contractile ring, the formation of which is temporally and spatially regulated following anaphase onset. Aurora- B is a member of the chromosomal passenger complex, which regulates various processes during mitosis; it is not understood, however, how Aurora-B is involved in cytokinesis. Here, we show that Aurora-B and myosin-IIB form a complex in vivo during telophase. Aurora-B phosphorylates the myosin-IIB rod domain at threonine 1847 (T1847), abrogating the ability of myosin-IIB monomers to form filaments. Furthermore, phosphorylation of myosin-IIB filaments by Aurora-B also promotes filament disassembly. We show that myosin-IIB possessing a phosphomimetic mutation at T1847 was unable to rescue cytokinesis failure caused by myosin-IIB depletion. Cells expressing a phosphoresistant mutation at T1847 had significantly longer intercellular bridges, implying that Aurora-Bmediated phosphorylation of myosin-IIB is important for abscission. We propose that myosin-IIB is a substrate of Aurora-B and reveal a new mechanism of myosin-IIB regulation by Aurora-B in the late stages of mitosis. [ABSTRACT FROM AUTHOR]

The microtubule-based mitotic spindle is responsible for equally partitioning the genome during each cell division, and its assembly is executed via several microtubule nucleation pathways. Targeting Protein for XKlp2 (TPX2) stimulates the branching microtubule nucleation pathway, where new microtubules are nucleated from preexisting ones within mitotic or meiotic spindles. TPX2, like other spindle assembly factors, is sequestered by binding to nuclear importins-α/β until the onset of mitosis, yet the molecular nature of this regulation remains unclear. Here we demonstrate that TPX2 interacts with importins-α/β with nanomolar affinity in a 1:1:1 monodispersed trimer. We also identify a new nuclear localization sequence in TPX2 that contributes to its high-affinity interaction with importin-α. In addition, we establish that TPX2 interacts with importin-β via dispersed, weak interactions. We show that interactions of both importin-α and -β with TPX2 inhibit its ability to undergo phase separation, which was recently shown to enhance the kinetics of branching microtubule nucleation. In summary, our study informs how importins regulate TPX2 to facilitate spindle assembly, and provides novel insight into the functional regulation of protein phase separation. [ABSTRACT FROM AUTHOR]