MAD2L1 supports MYC-driven liver carcinogenesis in mice and predicts poor prognosis in human hepatocarcinoma.

Mitotic arrest deficient 2 like 1 (MAD2L1) is a component of the mitotic spindle assembly checkpoint implicated in cancer cell proliferation and tumorigenesis. The functional role of MAD2L1 in hepatocellular carcinoma (HCC) has not been adequately investigated, especially in vivo. In the current manuscript, we sought to address the function of MAD2L1 in hepatocarcinogenesis. We found that MAD2L1 expression is upregulated in human HCCs, where its expression is associated with higher aggressive tumor grade, elevated proliferative activity, and poor prognosis. In human HCC cell lines, MAD2L1 knockdown led to decreased cell growth. Moreover, RNA-seq results demonstrated that MAD2L1 silencing induces the expression of genes associated with cell cycle, DNA replication, and various cancer-related pathways, supporting the critical role of MAD2L1 during HCC growth and differentiation. In a c-MYC-induced mouse HCC model, we revealed an increased expression of Mad2l1. Furthermore, Mad2l1 CRIPSR-mediated silencing prevented c-MYC-driven mouse liver development. Altogether, our study suggests that MAD2L1 plays a crucial role in hepatocarcinogenesis, and that its suppression could be a promising therapeutic strategy for treating human HCC.

Targeting MAD2B as a strategy for ischemic stroke therapy.

INTRODUCTION: Post-stroke cognitive impairment is one of the major causes of disability due to cerebral ischemia. MAD2B is an inhibitor of Cdh1/APC, and loss of Cdh1/APC function in mature neurons increases ROCK2 activity, leading to changes in synaptic plasticity and memory loss in mouse neurons. Whether MAD2B regulates learning memory capacity through ROCK2 in cerebral ischemia is not known. OBJECTIVES: We investigated the role and mechanism of MAD2B in cerebral ischemia-induced cognitive dysfunction. METHODS: The expression of MAD2B and its downstream related molecules was detected by immunoblotting and intervened with neuroprotectants after middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation/reoxygenation (OGD/R). We constructed MAD2B-cKO-specific knockout mice, knocked down and overexpressed MAD2B in mouse hippocampus by lentiviral injection in brain stereotaxis, modeled cerebral ischemia by using MCAO, and explored the role of MAD2B in post-stroke cognitive impairment (PSCI) by animal behaviors such as Y-maze and Novel object recognition test. Then the expression of MAD2B/ROCK2, downstream molecules and apoptosis-related molecules was detected. Finally, ROCK2 expression was intervened using its inhibitor and shRNA-ROCK2 lentivirus. RESULTS: The expression of MAD2B and its downstream molecules increased after MCAO and OGD/R. Nonetheless, this expression underwent a decline post-therapy with neuroprotective agents. Deletion of MAD2B in the hippocampus ameliorated memory and learning deficits and improved motor coordination in MCAO mice. Conversely, the overexpression of MAD2B in the hippocampus exacerbated learning and memory deficits. Deletion of MAD2B resulted in the downregulation of ROCK2/LIMK1/cofilin. It effectively reduced ischemia-induced upregulation of BAX and cleaved caspase-3, which could be reversed by MAD2B overexpression. Inhibition or knockdown of ROCK2 expression in primary cultured neurons led to the downregulation of LIMK1/cofilin expression and reduced the expression of apoptosis-associated molecules induced by ischemia. CONCLUSIONS: Our findings suggest that MAD2B affects neuronal apoptosis via Rock2, which affects neurological function and cerebral infarction.

Distinct roles of spindle checkpoint proteins in meiosis.

Gametes are produced via meiosis, a specialized cell division associated with frequent errors that cause birth defects and infertility. Uniquely in meiosis I, homologous chromosomes segregate to opposite poles, usually requiring their linkage by chiasmata, the products of crossover recombination.1 The spindle checkpoint delays cell-cycle progression until all chromosomes are properly attached to microtubules,2 but the steps leading to the capture and alignment of chromosomes on the meiosis I spindle remain poorly understood. In budding yeast meiosis I, Mad2 and Mad3BUBR1 are equally important for spindle checkpoint delay, but biorientation of homologs on the meiosis I spindle requires Mad2, but not Mad3BUBR1.3,4 Here we reveal the distinct functions of Mad2 and Mad3BUBR1 in meiosis I chromosome segregation. Mad2 promotes the prophase to metaphase I transition, while Mad3BUBR1 associates with the TOGL1 domain of Stu1CLASP, a conserved plus-end microtubule protein that is important for chromosome capture onto the spindle. Homologous chromosome pairs that are proficient in crossover formation but fail to biorient rely on Mad3BUBR1-Stu1CLASP to ensure their efficient attachment to microtubules and segregation during meiosis I. Furthermore, we show that Mad3BUBR1-Stu1CLASP are essential to rescue the segregation of mini-chromosomes lacking crossovers. Our findings define a new pathway ensuring microtubule-dependent chromosome capture and demonstrate that spindle checkpoint proteins safeguard the fidelity of chromosome segregation both by actively promoting chromosome alignment and by delaying cell-cycle progression until this has occurred.

Chronic spindle assembly checkpoint activation causes myelosuppression and gastrointestinal atrophy.

Interference with microtubule dynamics in mitosis activates the spindle assembly checkpoint (SAC) to prevent chromosome segregation errors. The SAC induces mitotic arrest by inhibiting the anaphase-promoting complex (APC) via the mitotic checkpoint complex (MCC). The MCC component MAD2 neutralizes the critical APC cofactor, CDC20, preventing exit from mitosis. Extended mitotic arrest can promote mitochondrial apoptosis and caspase activation. However, the impact of mitotic cell death on tissue homeostasis in vivo is ill-defined. By conditional MAD2 overexpression, we observe that chronic SAC activation triggers bone marrow aplasia and intestinal atrophy in mice. While myelosuppression can be compensated for, gastrointestinal atrophy is detrimental. Remarkably, deletion of pro-apoptotic Bim/Bcl2l11 prevents gastrointestinal syndrome, while neither loss of Noxa/Pmaip or co-deletion of Bid and Puma/Bbc3 has such a protective effect, identifying BIM as rate-limiting apoptosis effector in mitotic cell death of the gastrointestinal epithelium. In contrast, only overexpression of anti-apoptotic BCL2, but none of the BH3-only protein deficiencies mentioned above, can mitigate myelosuppression. Our findings highlight tissue and cell-type-specific survival dependencies in response to SAC perturbation in vivo.

REV7-p53 interaction inhibits ATM-mediated DNA damage signaling.

REV7 is an abundant, multifunctional protein that is a known factor in cell cycle regulation and in several key DNA repair pathways including Trans-Lesion Synthesis (TLS), the Fanconi Anemia (FA) pathway, and DNA Double-Strand Break (DSB) repair pathway choice. Thus far, no direct role has been studied for REV7 in the DNA damage response (DDR) signaling pathway. Here we describe a novel function for REV7 in DSB-induced p53 signaling. We show that REV7 binds directly to p53 to block ATM-dependent p53 Ser15 phosphorylation. We also report that REV7 is involved in the destabilization of p53. These findings affirm REV7's participation in fundamental cell cycle and DNA repair pathways. Furthermore, they highlight REV7 as a critical factor for the integration of multiple processes that determine viability and genome stability.

Identification of MAD2L1 and BUB1B as Potential Biomarkers Associated with Progression and Prognosis of Ovarian Cancer.

Ovarian cancer develops insidiously and is frequently diagnosed at advanced stages. Screening for ovarian cancer is an effective strategy for reducing mortality. This study aimed to investigate the molecular mechanisms underlying the development of ovarian cancer and identify novel tumor biomarkers for the diagnosis and prognosis of ovarian cancer. Three databases containing gene expression profiles specific to serous ovarian cancer (GSE18520, GSE12470, and GSE26712) were acquired. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes were analyzed for the differentially expressed gene (DEGs). The protein-protein interaction (PPI) network was constructed using the STRING database. The pivotal genes in the PPI network were screened using the Cytoscape software. Survival curve analysis was performed using a Kaplan-Meier Plotter. The cancer genome atlas and Gene Expression Omnibus databases were used to find the relationship between Hub gene and serous ovarian cancer. PCR and immunohistochemistry were used to detect the expression of Hub gene in serous ovarian cancer tissues and cells. Downstream pathways of the candidate tumor marker genes were predicted using Gene Set Enrichment Analysis. In this study, 252 DEGs were screened for pathway enrichment. 20 Hub genes were identified. Survival analysis suggested that Aurka, Bub1b, Cenpf, Cks1b, Kif20a, Mad2l1, Racgap1, and Ube2c were associated with the survival of patients with serous ovarian cancer. MAD2L1 and BUB1B levels were significantly different in serous ovarian cancer at different stages. Finally, Mad2l1 was found to play a role in the cell cycle, oocyte meiosis, and ubiquitin-mediated proteolysis. Meanwhile, Bub1b may play a role in the cell cycle, ubiquitin-mediated proteolysis, and spliceosome processes. Mad2l1 and Bub1b could be used as markers to predict ovarian carcinogenesis and prognosis, providing candidate targets for the diagnosis and treatment of serous ovarian cancer.

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

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

The promoting effect and mechanism of MAD2L2 on stemness maintenance and malignant progression in glioma.

BACKGROUND: Glioblastoma, the most common primary malignant tumor of the brain, is associated with poor prognosis. Glioblastoma cells exhibit high proliferative and invasive properties, and glioblastoma stem cells (GSCs) have been shown to play a crucial role in the malignant behavior of glioblastoma cells. This study aims to investigate the molecular mechanisms involved in GSCs maintenance and malignant progression. METHODS: Bioinformatics analysis was performed based on data from public databases to explore the expression profile of Mitotic arrest deficient 2 like 2 (MAD2L2) and its potential function in glioma. The impact of MAD2L2 on glioblastoma cell behaviors was assessed through cell viability assays (CCK8), colony formation assays, 5-Ethynyl-2'-deoxyuridine (EDU) incorporation assays, scratch assays, and transwell migration/invasion assays. The findings from in vitro experiments were further validated in vivo using xenograft tumor model. GSCs were isolated from the U87 and LN229 cell lines through flow cytometry and the stemness characteristics were verified by immunofluorescence staining. The sphere-forming ability of GSCs was examined using the stem cell sphere formation assay. Bioinformatics methods were conducted to identified the potential downstream target genes of MAD2L2, followed by in vitro experimental validation. Furthermore, potential upstream transcription factors that regulate MAD2L2 expression were confirmed through chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays. RESULTS: The MAD2L2 exhibited high expression in glioblastoma samples and showed significant correlation with patient prognosis. In vitro and in vivo experiments confirmed that silencing of MAD2L2 led to decreased proliferation, invasion, and migration capabilities of glioblastoma cells, while decreasing stemness characteristics of glioblastoma stem cells. Conversely, overexpression of MAD2L2 enhanced these malignant behaviors. Further investigation revealed that MYC proto-oncogene (c-MYC) mediated the functional role of MAD2L2 in glioblastoma, which was further validated through a rescue experiment. Moreover, using dual-luciferase reporter gene assays and ChIP assays determined that the upstream transcription factor E2F-1 regulated the expression of MAD2L2. CONCLUSION: Our study elucidated the role of MAD2L2 in maintaining glioblastoma stemness and promoting malignant behaviors through the regulation of c-MYC, suggesting its potential as a therapeutic target.

Mad2B forms a complex with Cdc20, Cdc27, Rev3 and Rev1 in response to cisplatin-induced DNA damage.

Mitotic arrest deficient 2 like 2 (Mad2L2, also known as Mad2B), the human homologue of the yeast Rev7 protein, is a regulatory subunit of DNA polymerase ζ that shares high sequence homology with Mad2, the mitotic checkpoint protein. Previously, we demonstrated the involvement of Mad2B in the cisplatin-induced DNA damage response. In this study, we extend our findings to show that Mad2B is recruited to sites of DNA damage in human cancer cells in response to cisplatin treatment. We found that in undamaged cells, Mad2B exists in a complex with Polζ-Rev1 and the APC/C subunit Cdc27. Following cisplatin-induced DNA damage, we observed an increase in the recruitment of Mad2B and Cdc20 (the activators of the APC/C), to the complex. The involvement of Mad2B-Cdc20-APC/C during DNA damage has not been reported before and suggests that the APC/C is activated following cisplatin-induced DNA damage. Using an in vitro ubiquitination assay, our data confirmed Mad2B-dependent activation of APC/C in cisplatin-treated cells. Mad2B may act as an accelerator for APC/C activation during DNA damage response. Our data strongly suggest a role for Mad2B-APC/C-Cdc20 in the ubiquitination of proteins involved in the DNA damage response.

Mad2 is dispensable for accurate chromosome segregation but becomes essential when oocytes are subjected to environmental stress.

Accurate chromosome segregation, monitored by the spindle assembly checkpoint (SAC), is crucial for the production of euploid cells. Previous in vitro studies by us and others showed that Mad2, a core member of the SAC, performs a checkpoint function in oocyte meiosis. Here, through an oocyte-specific knockout approach in mouse, we reconfirmed that Mad2-deficient oocytes exhibit an accelerated metaphase-to-anaphase transition caused by premature degradation of securin and cyclin B1 and subsequent activation of separase in meiosis I. However, it was surprising that the knockout mice were completely fertile and the resulting oocytes were euploid. In the absence of Mad2, other SAC proteins, including BubR1, Bub3 and Mad1, were normally recruited to the kinetochores, which likely explains the balanced chromosome separation. Further studies showed that the chromosome separation in Mad2-null oocytes was particularly sensitive to environmental changes and, when matured in vitro, showed chromosome misalignment, lagging chromosomes, and aneuploidy with premature separation of sister chromatids, which was exacerbated at a lower temperature. We reveal for the first time that Mad2 is dispensable for proper chromosome segregation but acts to mitigate environmental stress in meiotic oocytes.

Prolonged Cell Cycle Arrest in Response to DNA damage in Yeast Requires the Maintenance of DNA Damage Signaling and the Spindle Assembly Checkpoint.

Cells evoke the DNA damage checkpoint (DDC) to inhibit mitosis in the presence of DNA double-strand breaks (DSBs) to allow more time for DNA repair. In budding yeast, a single irreparable DSB is sufficient to activate the DDC and induce cell cycle arrest prior to anaphase for about 12 to 15 hours, after which cells "adapt" to the damage by extinguishing the DDC and resuming the cell cycle. While activation of the DNA damage-dependent cell cycle arrest is well-understood, how it is maintained remains unclear. To address this, we conditionally depleted key DDC proteins after the DDC was fully activated and monitored changes in the maintenance of cell cycle arrest. Degradation of Ddc2ATRIP, Rad9, Rad24, or Rad53CHK2 results in premature resumption of the cell cycle, indicating that these DDC factors are required both to establish and to maintain the arrest. Dun1 is required for establishment, but not maintenance of arrest, whereas Chk1 is required for prolonged maintenance but not for initial establishment of the mitotic arrest. When the cells are challenged with 2 persistent DSBs, they remain permanently arrested. This permanent arrest is initially dependent on the continuous presence of Ddc2 and Rad53; however, after 15 hours both proteins become dispensable. Instead, the continued mitotic arrest is sustained by spindle-assembly checkpoint (SAC) proteins Mad1, Mad2, and Bub2 but not by Bub2's binding partner Bfa1. These data suggest that prolonged cell cycle arrest in response to 2 DSBs is achieved by a handoff from the DDC to specific components of the SAC. Furthermore, the establishment and maintenance of DNA damage-induced cell cycle arrest requires overlapping but different sets of factors.

Distinct effects of heat shock temperatures on mitotic progression by influencing the spindle assembly checkpoint.

Heat shock is a physiological and environmental stress that leads to the denaturation and inactivation of cellular proteins and is used in hyperthermia cancer therapy. Previously, we revealed that mild heat shock (42 °C) delays the mitotic progression by activating the spindle assembly checkpoint (SAC). However, it is unclear whether SAC activation is maintained at higher temperatures than 42 °C. Here, we demonstrated that a high temperature of 44 °C just before mitotic entry led to a prolonged mitotic delay in the early phase, which was shortened by the SAC inhibitor, AZ3146, indicating SAC activation. Interestingly, mitotic slippage was observed at 44 °C after a prolonged delay but not at 42 °C heat shock. Furthermore, the multinuclear cells were generated by mitotic slippage in 44 °C-treated cells. Immunofluorescence analysis revealed that heat shock at 44 °C reduces the kinetochore localization of MAD2, which is essential for mitotic checkpoint activation, in nocodazole-arrested mitotic cells. These results indicate that 44 °C heat shock causes SAC inactivation even after full activation of SAC and suggest that decreased localization of MAD2 at the kinetochore is involved in heat shock-induced mitotic slippage, resulting in multinucleation. Since mitotic slippage causes drug resistance and chromosomal instability, we propose that there may be a risk of cancer malignancy when the cells are exposed to high temperatures.

Biallelic variants in MAD2L1BP (p31comet) cause female infertility characterized by oocyte maturation arrest.

Human oocyte maturation arrest represents one of the severe conditions for female patients with primary infertility. However, the genetic factors underlying this human disease remain largely unknown. The spindle assembly checkpoint (SAC) is an intricate surveillance mechanism that ensures accurate segregation of chromosomes throughout cell cycles. Once the kinetochores of chromosomes are correctly attached to bipolar spindles and the SAC is satisfied, the MAD2L1BP, best known as p31comet, binds mitosis arrest deficient 2 (MAD2) and recruits the AAA+-ATPase TRIP13 to disassemble the mitotic checkpoint complex (MCC), leading to the cell-cycle progression. In this study, by whole-exome sequencing (WES), we identified homozygous and compound heterozygous MAD2L1BP variants in three families with female patients diagnosed with primary infertility owing to oocyte metaphase I (MI) arrest. Functional studies revealed that the protein variants resulting from the C-terminal truncation of MAD2L1BP lost their binding ability to MAD2. cRNA microinjection of full-length or truncated MAD2L1BP uncovered their discordant roles in driving the extrusion of polar body 1 (PB1) in mouse oocytes. Furthermore, the patient's oocytes carrying the mutated MAD2L1BP resumed polar body extrusion (PBE) when rescued by microinjection of full-length MAD2L1BP cRNAs. Together, our studies identified and characterized novel biallelic variants in MAD2L1BP responsible for human oocyte maturation arrest at MI, and thus prompted new therapeutic avenues for curing female primary infertility.

Bridging Gaps in HDR Improvement: The Role of MAD2L2, SCAI, and SCR7.

This study aimed to enhance homology-directed repair (HDR) efficiency in CRISPR/Cas-mediated genome editing by targeting three key factors regulating the balance between HDR and non-homologous end joining (NHEJ): MAD2L2, SCAI, and Ligase IV. In order to achieve this, a cellular model using mutated eGFP was designed to monitor HDR events. Results showed that MAD2L2 knockdown and SCR7 treatment significantly improved HDR efficiency during Cas9-mediated HDR repair of the mutated eGFP gene in the HEK293T cell line. Fusion protein Cas9-SCAI did not improve HDR. This study is the first to demonstrate that MAD2L2 knockdown during CRISPR-mediated gene editing in HEK293T cells can increase precise correction by up to 10.2 times. The study also confirmed a moderate but consistent effect of SCR7, an inhibitor of Ligase IV, which increased HDR by 1.7 times. These findings provide valuable insights into improving HDR-based genome editing efficiency.

Maternal genetic polymorphisms in the major mitotic checkpoint genes MAD1L1 and MAD2L1 associated with the risk of survival in abnormal chromosomal fetuses.

Background: The genetic etiology of fetal chromosome abnormalities remains unknown, which brings about an enormous burden for patients, families, and society. The spindle assembly checkpoint (SAC) controls the normal procedure of chromosome disjunction and may take part in the process. Objective: The aim of this study was to explore the association between polymorphisms of MAD1L1 rs1801368 and MAD2L1 rs1283639804, involved in SAC and fetal chromosome abnormalities. Methods: The case-control study collected 563 cases and 813 health controls to test the genotypes of MAD1L1 rs1801368 and MAD2L1 rs1283639804 polymorphisms by polymerase chain reaction-restrictive fragment length polymorphism methods (PCR-RFLP). Results: MAD1L1 rs1801368 polymorphism was associated with fetal chromosome abnormalities alone or combined to lower homocysteine (HCY) levels (alone: dominant: OR: 1.75, 95%CI: 1.19-2.57, and p = 0.005; CT vs. CC: OR = 0.73, 95%CI: 0.57-0.94, and p = 0.016; lower HCY: C vs. T: OR = 0.74, 95%CI: 0.57-0.95, and p = 0.02; dominant: OR = 1.75, 95%CI: 0.79-1.92, and p = 0.005). No significant differences were found in other genetic models or subgroups (p > 0.05, respectively). MAD2L1 rs1283639804 polymorphism revealed a sole genotype in the studied population. HCY is significantly associated with fetal chromosome abnormalities in younger groups (OR: 1.78, 95%CI: 1.28-2.47, and p = 0.001). Conclusion: The results implied that the polymorphism of MAD1L1 rs1801368 may become the susceptibility factor to fetal chromosome abnormalities alone or combined to lower HCY levels but not to MAD2L1 rs1283639804 polymorphism. In addition, HCY significantly affects fetal chromosomal abnormalities in younger women.

The MAD2B-APC/C-MDM2 axis mediates acute kidney injury by modulating p53.

P53 is a master regulator modulating the progression of acute kidney injury (AKI). However, the mechanism underlying p53 regulation in AKI needs further investigation. Mitotic arrest deficient 2 like 2 (MAD2B) is a subunit of DNA polymerase ζ. Its role in AKI remains unclear. Here, we demonstrated that MAD2B acted as an endogenous suppressor of p53. MAD2B conditional knockout augmented the upregulation of p53 in kidneys suffering from cisplatin-induced AKI, therefore promoting the deterioration of renal function, G1 phase arrest and apoptosis of proximal tubular epithelial cells. Mechanistically, MAD2B deficiency activated the anaphase-promoting complex/cyclosome (APC/C), which is an inhibitor of the well-characterized p53-directed E3 ligase MDM2. The decreased MDM2 diminished the degradation of p53, resulting in the upregulation of p53. The APC/C antagonist proTAME ameliorated cisplatin-induced AKI and blocked MAD2B knockdown-induced p53 upregulation and reduced cell cycle arrest and apoptosis in tubular epithelial cells by upregulating MDM2. These results indicate that MAD2B is a novel target for inhibiting p53 and ameliorating AKI.

Separase and Roads to Disengage Sister Chromatids during Anaphase.

Receiving complete and undamaged genetic information is vital for the survival of daughter cells after chromosome segregation. The most critical steps in this process are accurate DNA replication during S phase and a faithful chromosome segregation during anaphase. Any errors in DNA replication or chromosome segregation have dire consequences, since cells arising after division might have either changed or incomplete genetic information. Accurate chromosome segregation during anaphase requires a protein complex called cohesin, which holds together sister chromatids. This complex unifies sister chromatids from their synthesis during S phase, until separation in anaphase. Upon entry into mitosis, the spindle apparatus is assembled, which eventually engages kinetochores of all chromosomes. Additionally, when kinetochores of sister chromatids assume amphitelic attachment to the spindle microtubules, cells are finally ready for the separation of sister chromatids. This is achieved by the enzymatic cleavage of cohesin subunits Scc1 or Rec8 by an enzyme called Separase. After cohesin cleavage, sister chromatids remain attached to the spindle apparatus and their poleward movement on the spindle is initiated. The removal of cohesion between sister chromatids is an irreversible step and therefore it must be synchronized with assembly of the spindle apparatus, since precocious separation of sister chromatids might lead into aneuploidy and tumorigenesis. In this review, we focus on recent discoveries concerning the regulation of Separase activity during the cell cycle.

The positive feedback loop of MAD2L1/TYK2/STAT3 induces progression in B-cell acute lymphoblastic leukaemia.

PURPOSE: Mitotic arrest deficient 2 like 1 (MAD2L1) has been extensively studied in several malignancies; however, its role in B-cell acute lymphoblastic leukaemia (B-ALL) remains unclear. METHODS: The expression of MAD2L1 was evaluated by real-time quantitative polymerase chain reaction. The biological functions of MAD2L1 in B-ALL were explored through Cell Counting Kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine assay (EDU), transwell assay, flow cytometry and xenograft models. The Western blotting and co-immunoprecipitation were utilized to evaluate the interplay between MAD2L1 and the TYK2/STAT3 pathway. The luciferase reporter and chromatin immunoprecipitation (ChIP) assay were employed to identify interactions between STAT3 and MAD2L1. RESULTS: We demonstrated that MAD2L1 was markedly upregulated in B-ALL, and its expression level not only correlated with the relapse and remission of the condition but also with a poor prognosis. MAD2L1 promoted the proliferation, migration and invasion of B-ALL cells in vitro and in vivo, whereas MAD2L1 knockdown had the opposite effects. Mechanistically, MAD2L1 induces the progression of B-ALL by activating the TYK2/STAT3 signaling pathway to phosphorylate. Interestingly, STAT3 induces the expression of MAD2L1 by binding directly to its promoter region, resulting in a positive-feedback loop of MAD2L1/TYK2/STAT3. CONCLUSION: This study uncovered a reciprocal loop of MAD2L1/TYK2/STAT3, which contributed to the development of B-ALL. Therefore, MAD2L1 can be considered a potential diagnostic biomarker as well as a novel therapeutic target for B-ALL.

Expression, regulating mechanism and therapeutic target of KIF20A in multiple cancer.

Kinesin family member 20A (KIF20A) is a member of the kinesin family. It transports chromosomes during mitosis, plays a key role in cell division. Recently, studies proved that KIF20A was highly expressed in cancer. High expression of KIF20A was correlated with poor overall survival (OS). In this review, we summarized all the cancer that highly expressed KIF20A, described the role of KIF20A in cancer. We also organized phase I and phase II clinical trials of KIF20A peptides vaccine. All results indicated that KIF20A was a promising therapeutic target for multiple cancer.

Inactivation of Mad2B Enhances Apoptosis in Human Cervical Cancer Cell Line upon Cisplatin-Induced DNA Damage.

Mad2B (Mad2L2), the human homolog of the yeast Rev7 protein, is a regulatory subunit of DNA polymerase ζ that shares sequence similarity with the mitotic checkpoint protein Mad2A. Previous studies on Mad2B have concluded that it is a mitotic checkpoint protein that functions by inhibiting the anaphase-promoting complex/cyclosome (APC/C). Here, we demonstrate that Mad2B is activated in response to cisplatin-induced DNA damage. Mad2B co-localizes at nuclear foci with DNA damage markers, such as proliferating cell nuclear antigen and gamma histone H2AX (γ-H2AX), following cisplatin-induced DNA damage. However, unlike Mad2A, the binding of Mad2B to Cdc20 does not inhibit the activity of APC/C in vitro. In contrast to Mad2A, Mad2B does not localize to kinetochores or binds to Cdc20 in spindle assembly checkpoint-activated cells. Loss of the Mad2B protein leads to damaged nuclei following cisplatin-induced DNA damage. Mad2B/Rev7 depletion causes the accumulation of damaged nuclei, thereby accelerating apoptosis in human cancer cells in response to cisplatin-induced DNA damage. Therefore, our results suggest that Mad2B may be a critical modulator of DNA damage response.