Stages Of Mitosis Research Articles

Impact of COVID-19 Pandemic on Delay of Melanoma Diagnosis: A Systematic Review and Meta-Analysis.

Several studies have described how the restrictive measures due to COVID-19 have delayed melanoma diagnoses, resulting in an increased rate of more severe cases. Summarizing the sparse results in this context might help to understand the real impact of the COVID-19 pandemic on melanoma. We conducted a systematic review and meta-analysis to investigate how the clinical and prognostic factors of new melanoma diagnoses changed after COVID-19. A literature search in MEDLINE, EMBASE, and Scopus was conducted in September 2023. We included studies published in peer-reviewed journals reporting histopathological data on new diagnoses of cutaneous melanoma in adult patients during and/or after the lockdown compared to those diagnosed before the COVID-19 pandemic. A meta-analysis was conducted utilizing a random effects model. The between-study heterogeneity was assessed via Higgins's I2 statistic. Publication bias was assessed using the Begg and Egger test. This study adhered to the updated PRISMA guidelines. The primary outcome was a comparison of melanoma thickness between the pre-COVID-19 and post-lockdown periods. The secondary outcomes were evaluations of the histopathological subtype, stage, and presence of ulceration and mitosis in melanomas diagnosed in these two pandemic phases. The study included 45 articles. We found a significantly higher proportion of all factors indicating worse prognosis in the post-lockdown period compared to the pre-COVID-19 phase, including high thickness (SOR = 1.14, 95%CI 1.08-1.20 for 1-2 mm; SOR = 1.62, 95%CI 1.08-2.40, for >2 mm), the presence of ulcerations (SOR = 1.35, 95%CI 1.18-1.54), nodular subtype (SOR = 1.19, 95%CI 1.07-1.32), the presence of mitosis (SOR = 1.57, 95% CI 1.17-2.11), and stage III (SOR = 1.39, 95%CI 1.19-1.52) and IV (SOR = 1.44, 95%CI 1.26-1.63). Limitations include the limited studies' geographical distribution and moderate heterogeneity affecting meta-analysis estimates. Our meta-analysis provided evidence of more advanced melanomas diagnosed in the post-COVID-19 pandemic period, emphasizing the importance of creating and updating pandemic preparedness plans to limit the impact of any future events on oncological care.

The number and distribution of proliferating cells in the rat’s rostral migratory stream as identified by means of two different proliferation markers

ABSTRACT In the brains of adult rodents, the cells arising in the subventricular zone of the lateral ventricles maintain the ability to divide when migrating to the olfactory bulb along the rostral migratory stream (RMS). Dividing cells in the RMS are most frequently revealed through immunohistochemical detection of an exogenous marker of proliferation, 5-Bromo-2-deoxyuridine (BrdU), which incorporates into DNA during the S-phase of mitosis. The more recently recognized antigen Ki-67 (also known as Kiel-67 and MKI67), an endogenous protein expressed in nuclei at all stages of mitosis, is also used for proliferation detection. BrdU and Ki-67 are often used as alternative methods, but they have not previously been compared in the RMS. We analyzed the numbers and distribution of cells labeled either with BrdU or Ki-67 within the RMS of adult rats. The first group of animals received a single i.p. dose of BrdU. In the second group, dividing cells were visualized by Ki-67 immunohistochemistry. Some sections from brains of BrdU-treated rats were also immunostained for Ki-67. Labeled cells were counted in the three anatomical parts of the RMS (vertical arm, elbow and horizontal arm) using a method for unbiased estimation of cell density. The distribution of proliferating cells was similar for both markers. Most BrdU and Ki-67 positive cells were located in the vertical arm and in the elbow, but a caudo-rostral reduction in cell divisions was more evident with Ki-67 labeling. The number of Ki-67 positive cells significantly exceeded the number of BrdU positive cells in all parts of the RMS. Our results indicate that BrdU and Ki-67 are not interchangeable markers for evaluation of proliferative activity in the RMS.

Scientific habilty by using DNA and robotic activities in the science class

Educational robotics as an area of pedagogy is a discipline whose objective is the development of robotic prototypes that support the learning of natural sciences, demonstrating its potential as a didactic proposal that integrates technology into transdisciplinary thinking favoring digital thinking in the 21st century, in which we can mention scientific ability and the development of solutions to problems that favor scientific thinking. This educational research aims to connect the fields of chemistry and biology with the growing technology of educational robotics. A descriptive interpretive methodology was applied to a group of 80 high school students; They conducted experimental activities such as extracting DNA from tomatoes and observing the stages of mitosis in onion apical meristems. After observing the chromosomes in a microscope, the students use an augmented reality application, contrasting the information and creating a robotic model with recyclable material, programmed using the open-source ap-plication Arduino. No significant differences were found during the development of the activities between public and private schools, showing that 90% of the students obtained the DNA and 67% managed to develop robotic programming activities.

Functions of HP1 in preventing chromosomal instability.

Chromosomal instability (CIN), caused by errors in the segregation of chromosomes during mitosis, is a hallmark of many types of cancer. The fidelity of chromosome segregation is governed by a sophisticated cellular signaling network, one crucial orchestrator of which is Heterochromatin protein 1 (HP1). HP1 dynamically localizes to distinct sites at various stages of mitosis, where it regulates key mitotic events ranging from chromosome-microtubule attachment to sister chromatid cohesion to cytokinesis. Our evolving comprehension of HP1's multifaceted role has positioned it as a central protein in the orchestration of mitotic processes.

Automatic detection of cell-cycle stages using recurrent neural networks.

Mitosis is the process by which eukaryotic cells divide to produce two similar daughter cells with identical genetic material. Research into the process of mitosis is therefore of critical importance both for the basic understanding of cell biology and for the clinical approach to manifold pathologies resulting from its malfunctioning, including cancer. In this paper, we propose an approach to study mitotic progression automatically using deep learning. We used neural networks to predict different mitosis stages. We extracted video sequences of cells undergoing division and trained a Recurrent Neural Network (RNN) to extract image features. The use of RNN enabled better extraction of features. The RNN-based approach gave better performance compared to classifier based feature extraction methods which do not use time information. Evaluation of precision, recall, and F-score indicates the superiority of the proposed model compared to the baseline. To study the loss in performance due to confusion between adjacent classes, we plotted the confusion matrix as well. In addition, we visualized the feature space to understand why RNNs are better at classifying the mitosis stages than other classifier models, which indicated the formation of strong clusters for the different classes, clearly confirming the advantage of the proposed RNN-based approach.

The LINC complex ensures accurate centrosome positioning during prophase.

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.

Cytological and transcriptomic analyses provide insights into the pollen fertility of synthetic allodiploid Brassica juncea hybrids.

Imbalanced chromosomes and cell cycle arrest, along with down-regulated genes in DNA damage repair and sperm cell differentiation, caused pollen abortion in synthetic allodiploid Brassica juncea hybrids. Interspecific hybridization is considered to be a major pathway for species formation and evolution in angiosperms, but the occurrence of pollen abortion in the hybrids is common, prompting us to recheck male gamete development in allodiploid hybrids after the initial combination of different genomes. Here, we investigated the several key meiotic and mitotic events during pollen development using the newly synthesised allodiploid B. juncea hybrids (AB, 2n=2× =18) as a model system. Our results demonstrated the partial synapsis and pairing of non-homologous chromosomes concurrent with chaotic spindle assembly, affected chromosome assortment and distribution during meiosis, which finally caused difference in genetic constitution amongst the final tetrads. The mitotic cell cycle arrest during microspore development resulted in the production of anucleate pollen cells. Transcription analysis showed that sets of key genes regulating cyclin (CYCA1;2 and CYCA2;3), DNA damage repair (DMC1, NBS1 and MMD1), and ubiquitin-proteasome pathway (SINAT4 and UBC) were largely downregulated at the early pollen meiosis stages, and those genes involved in sperm cell differentiation (DUO1, PIRL1, PIRL9 and LBD27) and pollen wall synthesis (PME48, VGDH11 and COBL10) were mostly repressed at the late pollen mitosis stages in the synthetic allodiploid B. juncea hybrids (AB). In conclusion, this study elucidated the related mechanisms affecting pollen fertility during male gametophyte development at the cytological and transcriptomic levels in the synthetic allodiploid B. juncea hybrids.

Diverse microtubule-targeted anticancer agents kill cells by inducing chromosome missegregation on multipolar spindles.

Microtubule-targeted agents are commonly used for cancer treatment, though many patients do not benefit. Microtubule-targeted drugs were assumed to elicit anticancer activity via mitotic arrest because they cause cell death following mitotic arrest in cell culture. However, we recently demonstrated that intratumoral paclitaxel concentrations are insufficient to induce mitotic arrest and rather induce chromosomal instability (CIN) via multipolar mitotic spindles. Here, we show in metastatic breast cancer and relevant human cellular models that this mechanism is conserved among clinically useful microtubule poisons. While multipolar divisions typically produce inviable progeny, multipolar spindles can be focused into near-normal bipolar spindles at any stage of mitosis. Using a novel method to quantify the rate of CIN, we demonstrate that cell death positively correlates with net loss of DNA. Spindle focusing decreases CIN and causes resistance to diverse microtubule poisons, which can be counteracted by addition of a drug that increases CIN without affecting spindle polarity. These results demonstrate conserved mechanisms of action and resistance for diverse microtubule-targeted agents. Trial registration: clinicaltrials.gov, NCT03393741.

Estimation of scots pine cytogenetic parameters under the conditions of industrial air pollution in European boreal forests.

Cytogenetic studies of Pinus sylvestris seed progeny have been carried out for the first time in the Murmansk region of Russia. Seeds were collected in the territory of 6 district forestries: Zelenoborsky, Kovdorsky, Kandalakshsky, Zasheikovsky, Umbsky and Nickelsky, which were at different distances from large copper-nickel plants. Analysis revealed higher S, Cu, and Ni content in Pinus sylvestris tree seeds from the Zasheikovsky and Nickelsky district forestries. Seeds from the Zelenoborsky district forestry had a higher Cu content (13.6 ± 0.5 mg/kg) compared to other areas. It was found that the frequency of mitotic pathologies in all areas of the study exceeded the level of spontaneous mutation in 5%. The most frequent aberrant cells were registered in the root meristem of seedlings from the Zasheikovsky district forestry, and their proportion averaged 9.4 ± 1.3% of the total number of cells studied at the metaphase and ana-telophase of mitosis stages. In Pinus sylvestris seedlings, micronuclei were noted in the cells at the interphase stage, often varying on average from 0.2 ± 0.1% in plants from the Kandalakshsky district forestry to 0.9 ± 0.3% from the Zasheikovsky district forestry. The data obtained testify to the colossal impact of heavy metals on the living organism cell genetic apparatus. The negative effect from industries, as sources of air pollutants, extends over tens of kilometers. Therefore, regularly monitoring the cytogenetic parameters of bioindicators such as Pinus sylvestris is necessary.

CELLULAR COMPOSITION OF THE LYMPHOID STRUCTURES OF THE HUMAN INTRAHEPATIC BILE DUCTS

he aim of our study was to investigate the cellular composition of the lymphoid structures of the human intrahepatic bile ducts. Materials and Methods: The object of the study was the lymphoid structures of the walls of the intrahepatic bile ducts obtained from 45 cadavers of different ages. Lymphoid nodules in the walls of the intrahepatic bile ducts were investigated by T. Hellman’s method. The microanatomy of lymphoid structures was studied on microscopic preparations. Microscopic preparations were stained according to Van Gieson, with hematoxylin-eosin, methylene blue. The digital data obtained during the study was subjected to statistical processing. Results: A macromicroscopic study of lymphoid formations in the intrahepatic bile ducts showed that lymphoid formations in the walls of these organs are represented by lymphoid nodules and diffuse lymphoid tissue. The peripheral contours of the lymphoid nodules are clearly defined. Histologically, the cellular composition of lymphoid nodules and diffuse lymphoid tissue was studied. In the mucous membrane and in the submucosa, small, medium sized lymphocytes, and large lymphocytes, macrophages, plasma, reticular, mast cells, cells in a stage of mitosis, degeneratively altered (destructive), and other forms of lymphoid cells are determined. Conclusions: According to our data, newborns have not only lymphoid nodules, but also a typical cellular composition in the lymphoid tissue, which has a completely “mature character”. The results of morphometric studies showed that in early childhood there is a high percentage of small, medium, large lymphocytes, macrophages, cells with signs of mitosis.

Endosomal Sorting Complex Required for Transport: The Molecular Machine for Ensuring Proper Mitosis.

Mitosis is a key step of eukaryote proliferation.Endosomal sorting complex required for transport, a protein complex closely associated with membrane shearing, is involved in endosome maturation, virus budding, and autophagy.The structural and functional abnormalities of the complex are associated with the occurrence and progression of cancer and other diseases.In this paper, we summarized the roles of the endosomal sorting complex required for transport in different stages of mitosis and reviewed the studies about the role of the complex in regulating mitosis in diseases.

Structural basis of centromeric cohesion protection

In the early stages of mitosis, cohesin is released from chromosome arms but not from centromeres. The protection of centromeric cohesin by SGO1 maintains the sister chromatid cohesion that resists the pulling forces of microtubules until all chromosomes are attached in a bipolar manner to the mitotic spindle. Here we present the X-ray crystal structure of a segment of human SGO1 bound to a conserved surface of the cohesin complex. SGO1 binds to a composite interface formed by the SA2 and SCC1RAD21 subunits of cohesin. SGO1 shares this binding interface with CTCF, indicating that these distinct chromosomal regulators control cohesin through a universal principle. This interaction is essential for the localization of SGO1 to centromeres and protects centromeric cohesin against WAPL-mediated cohesin release. SGO1–cohesin binding is maintained until the formation of microtubule–kinetochore attachments and is required for faithful chromosome segregation and the maintenance of a stable karyotype.

Antimitotic effects of <i>Cysticercus tenuicollis</i> protoscolexes extract at administration to mice and their negative consequences for organism

The purpose of the research is studying of Cysticercus tenuicollis protoscolexes extract effects on cell division at different routes of administration to mice and evaluation of the associated negative effects.Materials and methods. C. tenuicollis were obtained from spontaneously infected sheep in Kabardino-Balkarian Republic. C. tenuicollis protoscolexes were washed, crushed and homogenized. Protein extraction was performed with phosphate buffered saline pH 7.2–7.4. C. tenuicollis extract was administered intraperitoneally and intravenously to mice males at the dose level of 80 μg protein/animal. The control group of mice was intravenously injected with 0.1 ml of saline. At hours 3; 6; 24 and 48 post extract administration mice were euthanized. Bone marrow samples were taken from experimental and control mice for preparation of microscopic preparations to assess mitotic activity in a given cell population. The mitotic index was determined, all stages of mitosis were recorded. At the above time points blood samples were taken from mice to determine the main hematological parameters post intravenous and intraperitoneal administration of C. tenuicollis extract. The main hematological parameters of mice were determined using hematological analyzer MicroCC-20 Plus (High Technology, Inc. (USA)); leukocyte formula – by the generally accepted method. Samples of liver, kidneys, spleen, mesenteric lymph nodes and testes were taken from experimental and control animals for macroscopic and microscopic studies.Results and discussion. C. tenuicollis protoscolices extract leads to inhibition of cell division in the population bone marrow and testes cells in mice when administered intravenously and intraperitoneally at the dose level of 80 μg/animal manifested in accumulation of metaphases and decrease of other stages. At both routes of administration a decrease in leukocyte counts was noted. The observed microscopic changes in testes, spleen and lymph nodes either reflect the consequences of extract antimitotic effect or the immune response to the administration of C. tenuicollis extract.

Anti-Leukaemic Activity of Rilpivirine Is Mediated by Aurora A Kinase Inhibition

Acute myeloid leukaemia (AML) affects predominantly elderly people and has an incidence of 1% of all cancers and 2% of all cancer deaths. Despite using intensive chemotherapy and allogeneic stem cell transplantation, the treatment options for AML remain open for innovation. Thus, there is a need to explore alternative therapies such as less toxic targeted therapies in AML. Aurora A kinase is a well-established target for the treatment of various cancers, including AML. This kinase plays a pivotal role in the cell-division cycle, particularly in different stages of mitosis, and is also involved in many other cellular regulatory processes. In a previous study, we demonstrated that the anti-viral drug rilpivirine is an Aurora A kinase inhibitor. In the current study, we have further explored the selectivity of rilpivirine for Aurora A kinase inhibition by testing this drug against a panel of 429 kinases. Concurrently, we demonstrated that rilpivirine significantly inhibited the proliferation of AML cells in a time- and concentration-dependent manner that was preceded by G2/M cell-cycle arrest leading to the induction of apoptosis. Consistent with its kinase inhibitory role, rilpivirine modulated the expression of critical proteins in the Aurora A kinase-signalling pathway. Importantly, orally administered rilpivirine significantly inhibited tumour growth in an HL-60 xenograft model without showing body weight changes or other clinical signs of toxicity. Furthermore, rilpivirine enhanced the anti-proliferative efficacy of the conventional anti-leukaemic chemotherapeutic agent cytarabine. Collectively, these findings provide the stimulus to explore further the anti-leukaemic activity of the anti-viral drug rilpivirine.

Heat stress responses vary during floret development in European spring barley cultivars.

The Poaceae, or grasses, include many agriculturally important cereal crops such as rice (Oryza sativa), maize (Zea mays), barley (Hordeum vulgare) and bread wheat (Triticum aestivum). Barley is a widely grown cereal crop used for stock feed, malting and brewing. Abiotic stresses, particularly global warming, are the major causes of crop yield losses by affecting fertility and seed set. However, effects of heat stress on reproductive structures and fertility in barley have not been extensively investigated. In this study we examined three commercial European spring barley varieties under high temperature conditions to investigate the effects on floret development. Using a combination of fertility assays, X-ray micro computed tomography, 3-dimensional modelling, cytology and immunolabelling, we observed that male reproductive organs are severely impacted by increased temperature, while the female reproductive organs are less susceptible. Importantly, the timing of stress relative to reproductive development had a significant impact on fertility in a cultivar-dependent manner, this was most significant at pollen mitosis stage with fertility ranged from 31.6-56.0% depending on cultivar. This work provides insight into how heat stress, when applied during male pollen mother cell meiosis and pollen mitosis, affects barley fertility and seed set, and also describes complementary invasive and non-invasive techniques to investigate floret development. This information will be used to identify and study barley cultivars that are less susceptible to heat stress at specific stages of floral development.

Effects of <i>Trichinella spiralis</i> and <i>Echinococcus multilocularis</i> extracts after single and multiple injections on mitosis and hematological and biochemical parameters of mice

The purpose of the research is to study effects of Trichinella spiralis and Echinococcus multilocularis extracts on mitosis in a bone marrow cell population, and on hematological and biochemical blood parameters of mice after single and multiple intraperitoneal injections.Materials and methods. The experiment was conducted on outbred male mice. The T. spiralis and E. multilocularis extracts were administered intraperitoneally once or multiple times daily for 10 days at a dose of 80 μg/mouse. Bone marrow cell isolation, microscopic preparations, mitotic index and individual stage determination were made as described in the literature (Ford C. E., Hamerton J. L., 1956). The mouse main peripheral blood parameters were determined with a MicroCC-20 Plus hematological analyzer, and the leucogram was determined by a conventional method. Biochemical blood parameters of the mice were determined with a Clima MC-15 analyzer.Results and discussion. The T. spiralis and E. multilocularis extracts after a single intraperitoneal injection at a dose of 80 μg/ mouse had a pronounced negative effect on the mouse bone marrow cell mitosis with the cell division terminated in the metaphase and a decreased proportion of other mitosis stages. Characteristics were detected of the effects made by the T. spiralis and E. multilocularis extracts on the mouse bone marrow cell mitosis after multiple administration for 10 days. In the reinjection mode of the test extracts to the mice, hematological and biochemical parameters did not change.

Machine learning and deep learning for breast cancer risk prediction and diagnosis: a Survey

Breast cancer is the widest spreading disease among women globally. The prevalence rate of breast cancer continued to rise in the last few decades. The mitotic count is a relevant factor for grading invasive breast cancer. Early analysis is an extremely imperative step in treatment. However, it is not an easy one due to several skepticisms in detection which employ mammograms. Since it is subject to human prone error, requires more time for completion and the nuclei look similar during all stages of mitosis, automatic detection of mitosis is a good solution to overcome these problems. Detailed analysis of breast cancer normally requires medical images of different methods. The sensitivity and specificity of the diagnosis largely depend on the experiences of the radiologists, and uncertain diagnosis is quite frequent because of resolution limitations and the concerns of lawsuits arisen from wrong diagnosis or undetected lesions. In this paper, the top methodologies used for mitosis detection are analyzed. There are many algorithms for classification and prediction of breast cancer: Support Vector Machine (SVM), Decision Tree (CART), k Nearest Neighbors (KNN), Random Forest (RF), and Bayesian Networks (BN). The Wisconsin data set was used to analyze breast cancer as a training set to assess and measure the performance of the three ML classifiers in terms of key frameworks such as accuracy, recall, precision, and ROC. The outcome obtained in this paper provides a critique of the stateofart ML techniques for breast cancer detection. It was also found that the ensemble classifier gives better performance. A preliminary experiment conducted on cascaded RF and Artificial Neural Network (ANN) results in better accuracy than individual classifiers. The paper shows how we can use deep learning technology diagnosis of breast cancer using MIAS Dataset. A deep learning approach is almost used for immense task objective Image processing, Computer Vision, Medical Diagnosis, and Neural Language Processing.

Pituitary Adenylate Cyclase-activating Polypeptide (PACAP) -derived Peptide MPAPO Stimulates Adipogenic Differentiation by Regulating the Early Stage of Adipogenesis and ERK Signaling Pathway.

Regenerative medicine and tissue engineering have delivered new healing possibilities to the treatment of soft tissue defects, but the selection of seed cells is critical for treatment. Adipose-derived stem cells have perpetually been a preferred candidate for seed cells due to their wealthy sources, simple access, high plasticity, and powerful value-added capabilities. How to improve the efficiency of adipogenic differentiation is the key to the treatment. Pituitary adenylate cyclase-activating peptide, as a biologically active peptide secreted by the pituitary, is widely involved in regulating the body's sugar metabolism and lipid metabolism. However, the effects of MPAPO in ADSCs adipogenic differentiation remain unknown. Our results reveal that MPAPO treatment improves the adipogenic differentiation efficiency of ADSCs, including promoting the accumulation of lipid droplets and triglycerides, and the expression of adipocyte protein biomarkers PPARγ and C/EBPa. Additionally, the mechanism studies showed that the effective window of MPAPO-induced adipogenesis was the first 3 days during ADSCs differentiation. MPAPO selectively binds to the PAC1 receptor and promotes adipogenic differentiation of ADSCs by activating the ERK signaling pathway and elevating cell proliferation during postconfluent mitosis stage. Altogether, we demonstrate that MPAPO plays a crucial role in ADSCs adipogenesis, providing experimental basis and data for exploring therapeutic options in tissue defect repair.

Spindle and Kinetochore-Associated Complex Is Associated With Poor Prognosis in Adrenocortical Carcinoma.

The spindle and kinetochore-associated (SKA) complex, composed of three subunits (SKA1, SKA2, and SKA3), stabilizes spindle microtubule attachment to the kinetochore (KT) in the middle stage of mitosis. High expression of this complex is associated with poor prognosis for several tumors. However, the potential role of SKA complex overexpression in rare malignant diseases, such as adrenocortical carcinoma (ACC), has not been well investigated. In this study, we used several databases to explore the relationship between SKA subunit expression and prognosis in ACC patients. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) databases were used to analyze enriched pathways in ACC. The results suggest that each of the three SKA subunits are overexpressed in ACC and that high expression is correlated with poor patient prognosis. Overexpression of the SKA complex is associated with the expression of organelle fission, nuclear division, and chromosome segregation pathways. Furthermore, differential expression of hub genes for proteins that interact physically or functionally with the SKA complex (CCNB2, UBE2C, BUB1B, TPX2, CCNA2, CDCA8, CCNB1, MELK, TOP2A, and KIF2C) revealed additional potential biomarkers for ACC. Our findings provide additional understanding of the mechanisms of ACC and suggest an approach for biomarker discovery using publicly available resources.

Role of phosphorylation of Cdc20 in the regulation of the action of APC/C in mitosis

The ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome) is essential for the control of mitosis, and its activity is subject to tight regulation. In early mitosis, APC/C is inhibited by the mitotic checkpoint system, but subsequently it regains activity and promotes metaphase-anaphase transition by targeting cyclin B and securin for degradation. The phosphorylation of APC/C by the mitotic protein kinase Cdk1-cyclin B facilitates its interaction with its coactivator Cdc20, while the phosphorylation of Cdc20 inhibits its binding to APC/C. This raises the question of how Cdc20 binds to APC/C under conditions of high Cdk1 activity. It seemed possible that the opposing action of protein phosphatases produces a fraction of unphosphorylated Cdc20 that binds to APC/C. We found, however, that while inhibitors of protein phosphatases PP2A and PP1 increased the overall phosphorylation of Cdc20 in anaphase extracts from Xenopus eggs, they did not decrease the levels of Cdc20 bound to APC/C. Searching for alternative mechanisms, we found that following the binding of Cdc20 to APC/C, it became significantly protected against phosphorylation by Cdk1. Protection was mainly at threonine sites at the N-terminal region of Cdc20, known to affect its interaction with APC/C. A model is proposed according to which a pool of unphosphorylated Cdc20, originating from initial stages of mitosis or from phosphatase action, combines with phosphorylated APC/C and thus becomes stabilized against further phosphorylation, possibly by steric hindrance of Cdk1 action. This pool of APCCdc20 appears to be required for the regulation of APC/C activity at different stages of mitosis.