Separase: Function Beyond Cohesion Cleavage and an Emerging Oncogene

PAX2 mediated upregulation of ESPL1 contributes to cisplatin resistance in bladder cancer through activating the JAK2/STAT3 pathway

Extra spindle-polar body like 1 (ESPL1) is associated with the development of a variety of cancers, including bladder cancer, and is closely related to chemoresistance. In this study, we aimed to reveal the role of ESPL1 in bladder cancer progression and cisplatin (DDP) resistance. First, ESPL1 was found to be highly expressed in tumor tissues and cells of bladder cancer, and more highly expressed in cisplatin resistant tumor tissues or cells. The binding of PAX2 in ESPL1 promoter region was predicted by Jaspar database and verified by Ch-IP analysis and the luciferase reporter gene assay. Next, cisplatin-resistant T24 cells (T24/DDP) were established and transfected with ESPL1 siRNA (si-ESPL1) or overexpression vector (pcDNA-ESPL1) or co-transfected with PAX2 siRNA (si-PAX2) or overexpression vector (pcDNA-PAX2), and then treated with DDP or AG490, an inhibitor of JAK2. The results showed that silencing ESPL1 significantly reduced T24/DDP cell viability, colony formation and invasion, enhanced sensitivity to DDP, and induced cell apoptosis. Silencing PAX2 decreased ESPL1 expression, enhanced sensitivity to DDP, and induced apoptosis of T24/DDP cells, and inhibited activation of JAK2/STAT3 pathway. Overexpressing ESPL1 reversed the effect of PAX2 silencing on T24/DDP cells, while AG490 counteracted the reversal effect of overexpressing ESPL1. Finally, a xenograft tumor model was established and found that silencing ESPL1 or DDP treatment inhibited tumor growth, while silencing ESPL1 combined with DDP treatment had the best effect. In summary, this study suggested that PAX2-mediated ESPL1 transcriptional activation enhanced cisplatin resistance in bladder cancer by activating JAK2/STAT3 pathway.

Upregulation of ESPL1 is associated with poor prognostic outcomes in endometrial cancer

BACKGROUND

Extra spindle pole bodies-like 1 (ESPL1) is known to play a crucial role in the segregation of sister chromatids during mitosis. Overexpression of ESPL1 is considered to have oncogenic effects in various human cancers. However, the specific biological function of ESPL1 in endometrial cancer (EC) remains unclear.

METHODS

The TCGA and GEO databases were utilized to assess the expression of ESPL1 in EC. Immunohistochemistry was utilized to detect separase expression in EC samples. Kaplan-Meier survival analysis and Cox regression analysis were performed to evaluate the diagnostic and prognostic significance of ESPL1 in EC. Gene Set Enrichment Analysis (GSEA) was employed to explore the potential signaling pathway of ESPL1 in EC. Cell proliferation and colony formation ability were analyzed using CCK-8 and colony formation assay.

RESULTS

Our analysis revealed that ESPL1 is significantly upregulated in EC, and its overexpression is associated with advanced clinical characteristics and unfavourable prognostic outcomes. Suppression of ESPL1 attenuated proliferation of EC cell line.

CONCLUSION

The upregulation of ESPL1 is associated with advanced disease and poor prognosis in EC patients. These findings suggest that ESPL1 has the potential to serve as a diagnostic and prognostic biomarker in EC, highlighting its significance in the management of EC patients.

Genome-wide CRISPR screen identifies ESPL1 limits the response of gastric cancer cells to apatinib

Apatinib was the first anti-angiogenic agent approved for treatment of metastatic gastric cancer (GC). However, the emergence of resistance was inevitable. Thus investigating new and valuable off-target effect of apatinib directly against cancer cells is of great significance. Here, we identified extra spindle pole bodies-like 1 (ESPL1) was responsible for apatinib resistance in GC cells through CRISPR genome-wide gain-of-function screening. Loss of function studies further showed that ESPL1 inhibition suppressed cell proliferation, migration and promoted apoptosis in vitro, and accordingly ESPL1 knockdown sensitized GC cells to apatinib. In addition, we found ESPL1 interacted with mouse double minute 2 (MDM2), a E3 ubiquitin protein ligase, and the combination of MDM2 siRNA with apatinib synergistically ameliorated the resistance induced by ESPL1 overexpression. In summary, our study indicated that ESPL1 played a critical role in apatinib resistance in GC cells. Inhibition of MDM2 could rescue the sensitivity of GC cells to apatinib and reverse ESPL1-mediated resistance.

The molecular mechanisms of human separase regulation

Sister chromatid segregation is the final irreversible step of mitosis. It is initiated by a complex regulatory system that ultimately triggers the timely activation of a conserved cysteine protease named separase. Separase cleaves the cohesin protein ring that links the sister chromatids and thus facilitates their separation and segregation to the opposite poles of the dividing cell. Due to the irreversible nature of this process, separase activity is tightly controlled in all eukaryotic cells. In this mini-review, we summarize the latest structural and functional findings on the regulation of separase, with an emphasis on the regulation of the human enzyme by two inhibitors, the universal inhibitor securin and the vertebrate-specific inhibitor CDK1-cyclin B. We discuss the two fundamentally different inhibitory mechanisms by which these inhibitors block separase activity by occluding substrate binding. We also describe conserved mechanisms that facilitate substrate recognition and point out open research questions that will guide studies of this fascinating enzyme for years to come.

Stem cells' centrosomes: How can organelles identified 130 years ago contribute to the future of regenerative medicine?

At the core of regenerative medicine lies the expectation of repair or replacement of damaged tissues or whole organs. Donor scarcity and transplant rejection are major obstacles, and exactly the obstacles that stem cell-based therapy promises to overcome. These therapies demand a comprehensive understanding of the asymmetric division of stem cells, i.e. their ability to produce cells with identical potency or differentiated cells. It is believed that with better understanding, researchers will be able to direct stem cell differentiation. Here, we describe extraordinary advances in manipulating stem cell fate that show that we need to focus on the centrosome and the centrosome-derived primary cilium. This belief comes from the fact that this organelle is the vehicle that coordinates the asymmetric division of stem cells. This is supported by studies that report the significant role of the centrosome/cilium in orchestrating signaling pathways that dictate stem cell fate. We anticipate that there is sufficient evidence to place this organelle at the center of efforts that will shape the future of regenerative medicine.

Impact of Global Transcriptional Silencing on Cell Cycle Regulation and Chromosome Segregation in Early Mammalian Embryos

The onset of an early development is, in mammals, characterized by profound changes of multiple aspects of cellular morphology and behavior. These are including, but not limited to, fertilization and the merging of parental genomes with a subsequent transition from the meiotic into the mitotic cycle, followed by global changes of chromatin epigenetic modifications, a gradual decrease in cell size and the initiation of gene expression from the newly formed embryonic genome. Some of these important, and sometimes also dramatic, changes are executed within the period during which the gene transcription is globally silenced or not progressed, and the regulation of most cellular activities, including those mentioned above, relies on controlled translation. It is known that the blastomeres within an early embryo are prone to chromosome segregation errors, which might, when affecting a significant proportion of a cell within the embryo, compromise its further development. In this review, we discuss how the absence of transcription affects the transition from the oocyte to the embryo and what impact global transcriptional silencing might have on the basic cell cycle and chromosome segregation controlling mechanisms.

Identification and analysis of genes associated with epithelial ovarian cancer by integrated bioinformatics methods

Background

Though considerable efforts have been made to improve the treatment of epithelial ovarian cancer (EOC), the prognosis of patients has remained poor. Identifying differentially expressed genes (DEGs) involved in EOC progression and exploiting them as novel biomarkers or therapeutic targets is of great value.

Methods

Overlapping DEGs were screened out from three independent gene expression omnibus (GEO) datasets and were subjected to Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses. The protein-protein interactions (PPI) network of DEGs was constructed based on the STRING database. The expression of hub genes was validated in GEPIA and GEO. The relationship of hub genes expression with tumor stage and overall survival and progression-free survival of EOC patients was investigated using the cancer genome atlas data.

Results

A total of 306 DEGs were identified, including 265 up-regulated and 41 down-regulated. Through PPI network analysis, the top 20 genes were screened out, among which 4 hub genes, which were not researched in depth so far, were selected after literature retrieval, including CDC45, CDCA5, KIF4A, ESPL1. The four genes were up-regulated in EOC tissues compared with normal tissues, but their expression decreased gradually with the continuous progression of EOC. Survival curves illustrated that patients with a lower level of CDCA5 and ESPL1 had better overall survival and progression-free survival statistically.

Conclusion

Two hub genes, CDCA5 and ESPL1, identified as probably playing tumor-promotive roles, have great potential to be utilized as novel therapeutic targets for EOC treatment.

Cellular Control of Protein Turnover via the Modification of the Amino Terminus

The first amino acid of a protein has an important influence on its metabolic stability. A number of ubiquitin ligases contain binding domains for different amino-terminal residues of their substrates, also known as N-degrons, thereby mediating turnover. This review summarizes, in an exemplary way, both older and more recent findings that unveil how destabilizing amino termini are generated. In most cases, a step of proteolytic cleavage is involved. Among the over 500 proteases encoded in the genome of higher eukaryotes, only a few are known to contribute to the generation of N-degrons. It can, therefore, be expected that many processing paths remain to be discovered.

Serum ESPL1 Can Be Used as a Biomarker for Patients With Hepatitis B Virus-Related Liver Cancer: A Chinese Case-Control Study

AIMS

To investigate the feasibility of serum extra spindle pole bodies-like 1 (ESPL1) used as a biomarker for patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC).

METHODS

131 chronic HBV-infection patients were recruited and divided into HBV S gene integration, non-HBV S gene integration, chronic hepatitis B (CHB), HBV-related liver cirrhosis (LC) and HBV-related HCC group, 24 non-HBV-related HCC patients were selected as HCC control group, 30 people without HBV-infection as healthy control group. Serum ESPL1 were detected and compared.

RESULTS

ESPL1 level of integration group was significantly higher than that of non-integration group (346.7 vs 199.6 ng/ml, P = 0.000) and healthy control group (346.7 vs 41.3 ng/ml, P = 0.000). ESPL1 level of non-integration group was significantly higher than that of healthy control group (199.6 vs 41.3 ng/ml, P = 0.000); ESPL1 levels in chronic HBV-infection related groups were increased in turn according to CHB group (95.8 ng/ml), HBV-related LC group (268.2 ng/ml), HBV-related HCC group (279.9 ng/ml) and integration group (346.7 ng/ml). Except that there was no significant difference in ESPL1 levels between HBV-related LC and HCC group (P = 0.662), pairwise comparisons between other groups showed significant differences (P < 0.05). ESPL1 level of HBV-related HCC group was significantly higher than that of non-HBV-related HCC group (279.9 vs 46.6 ng/ml, P = 0.000), there was no noticeable difference between non-HBV-related HCC and healthy control group (46.6 vs 41.3 ng/ml, P = 0.848). ESPL1 level of HBV-related HCC group after resection was significantly lower than that of before resection (178.4 vs 260.8 ng/ml, P = 0.000).

CONCLUSIONS

Chronic HBV-infection patients with high ESPL1 level may indicate HBV S gene integration and is a high-risk population for HBV-related HCC. Serum ESPL1 can be used as a biomarker for screening HBV-related HCC high-risk population and monitoring recurrence.

Combined Analysis of DNA Methylome and Transcriptome Reveal Novel Candidate Genes Related to Porcine Escherichia coli F4ab/ac-Induced Diarrhea

Enterotoxigenic Escherichia coli (ETEC) that express F4 (K88) fimbriae are the principal microorganisms responsible for bacterial diarrhea in neonatal and pre-weaning piglets. To better understand the molecular effects of ETEC F4ab/ac infection, we performed a genome-wide comparison of the changes in DNA methylation and gene expression in ETEC F4ab/ac infected porcine intestinal epithelial cells. We characterized the pattern of changes in methylation and found 3297 and 1593 differentially methylated regions in cells infected with F4ab and F4ac, respectively. Moreover, 606 and 780 differentially expressed genes (DEGs) in ETEC F4ab and F4ac infected cells were detected and these genes were highly enriched in immune/defense response related pathways. Integrative analysis identified 27 and 10 genes showing inverse correlations between promoter methylation and expression with ETEC F4ab/ac infection. Altered DNA methylation and expression of various genes suggested their roles and potential functional interactions upon ETEC F4ab/ac infection. Further functional analyses revealed that three DEGs (S100A9, SGO1, and ESPL1) in F4ab infected cells and three DEGs (MAP3K21, PAK6, and MPZL1) in F4ac infected cells are likely involved in the host cells response to ETEC infection. Our data provides further insight into the epigenetic and transcriptomic alterations of ETEC F4ab/ac infected porcine intestinal epithelial cells, and may advance the identification of biomarkers and drug targets for predicting susceptibility to and controlling ETEC F4ab/ac induced diarrhea.

Separase activity distribution can be a marker of major molecular response and proliferation of CD34+ cells in TKI-treated chronic myeloid leukemia patients

Separase, a cysteine endopeptidase, is a key player in mitotic sister chromatid separation, replication fork dynamics, and DNA repair. Aberrant expression and/or altered separase proteolytic activity are associated with aneuploidy, tumorigenesis, and disease progression. Since genomic instability and clonal evolution are hallmarks of progressing chronic myeloid leukemia (CML), we have comparatively examined separase proteolytic activity in TKI-treated chronic phase CML. Separase proteolytic activity was analyzed on single cell level in 88 clinical samples and in 14 healthy controls by a flow cytometric assay. In parallel, BCR-ABL1 gene expression and replication fork velocity were measured by qRT-PCR and DNA fiber assays, respectively. The separase activity distribution (SAD) value indicating the occurrence of MNCs with elevated separase proteolytic activity within samples was found to positively correlate with BCR-ABL1 gene expression levels and loss of MMR (relapse) throughout routine BCR-ABL1 monitoring. Analyses of CD34⁺ cells and MNCs fractionized by flow cytometric cell sorting according to their separase activity levels (H- and L-fractions) revealed that CD34⁺ cells with elevated separase activity levels (H-fractions) displayed enhanced proliferation/viability when compared with cells with regular (L-fraction) separase activity (mean 3.3-fold, p = 0.0011). BCR-ABL1 gene expression positivity prevailed in MNC H-fractions over L-fractions (42% vs. 8%, respectively). Moreover, expanding CD34⁺ cells of H-fractions showed decreased replication fork velocity compared with cells of L-fractions (p < 0.0001). Our data suggests an association between high separase activity, residual BCR-ABL1 gene expression, and enhanced proliferative capacity in hematopoietic cells within the leukemic niche of TKI-treated chronic phase CML.

Bioinformatics Analysis Identified Key Molecular Changes in Bladder Cancer Development and Recurrence

Background and Objectives: Bladder cancer (BC) is a complex tumor associated with high recurrence and mortality. To discover key molecular changes in BC, we analyzed next-generation sequencing data of BC and surrounding tissue samples from clinical specimens. Methods. Gene expression profiling datasets of bladder cancer were analyzed online. The Database for Annotation, Visualization, and Integrated Discovery (DAVID, https://david.ncifcrf.gov/) was used to perform Gene Ontology (GO) functional and KEGG pathway enrichment analyses. Molecular Complex Detection (MCODE) in Cytoscape software (Cytoscape_v3.6.1) was applied to identify hub genes. Protein expression and survival data were downloaded from OncoLnc (http://www.oncolnc.org/). Gene expression data were obtained from the ONCOMINE website (https://www.oncomine.org/). Results. We identified 4211 differentially expressed genes (DEGs) by analysis of surrounding tissue vs. cancer tissue (SC analysis) and 410 DEGs by analysis of cancer tissue vs. recurrent tissue cluster (CR analysis). GO function analysis revealed enrichment of DEGs in genes related to the cytoplasm and nucleoplasm for both clusters, and KEGG pathway analysis showed enrichment of DEGs in the PI3K-Akt signaling pathway. We defined the 20 genes with the highest degree of connectivity as the hub genes. Cox regression revealed CCNB1, ESPL1, CENPM, BLM, and ASPM were related to overall survival. The expression levels of CCNB1, ESPL1, CENPM, BLM, and ASPM were 4.795-, 5.028-, 8.691-, 2.083-, and 3.725-fold higher in BC than the levels in normal tissues, respectively. Conclusions. The results suggested that the functions of CCNB1, ESPL1, CENPM, BLM, and ASPM may contribute to BC development and the functions of CCNB1, ESPL1, CENPM, and BLM may also contribute to BC recurrence.

Characterization of a novel separase-interacting protein and candidate new securin, Eip1p, in the fungal pathogen Candida albicans

Proper chromosome segregation is crucial for maintaining genomic stability and dependent on separase, a conserved and essential cohesin protease. Securins are key regulators of separases, but remain elusive in many organisms due to sequence divergence. Here, we demonstrate that the separase homologue Esp1p in the ascomycete Candida albicans, an important pathogen of humans, is essential for chromosome segregation. However, C. albicans lacks a sequence homologue of securins found in model ascomycetes. We sought a functional homologue through identifying Esp1p interacting factors. Affinity purification of Esp1p and mass spectrometry revealed Esp1p-Interacting Protein1 (Eip1p)/Orf19.955p, an uncharacterized protein specific to Candida species. Functional analyses demonstrated that Eip1p is important for chromosome segregation but not essential, and modulated in an APCCdc20-dependent manner, similar to securins. Eip1p is strongly enriched in response to methyl methanesulfate (MMS) or hydroxyurea (HU) treatment, and its depletion partially suppresses an MMS or HU-induced metaphase block. Further, Eip1p depletion reduces Mcd1p/Scc1p, a cohesin subunit and separase target. Thus, Eip1p may function as a securin. However, other defects in Eip1p-depleted cells suggest additional roles. Overall, the results introduce a candidate new securin, provide an approach for identifying these divergent proteins, reveal a putative anti-fungal therapeutic target, and highlight variations in mitotic regulation in eukaryotes.

Expression and prognostic value of cell-cycle-associated genes in gastric adenocarcinoma

Background

Gastric carcinoma is a malignant disease, and gastric adenocarcinoma (GAC) is the most common histological type. Molecular profiling of GAC has been extensively performed, but few have focused on the clinical significance of gene clusters of the cell cycle.

Methods

We investigated the genetic profile of cell-cycle-associated genes in a GAC cohort. The mRNA expression and clinical data were downloaded from TCGA, according to cBioportal. We conducted a series of analyses to detect the relationships between these genes and GAC.

Results

From all the patients, 5 clusters were identified based on mRNA expression of 122 cell-cycle-associated genes. Cluster 1 showed the worst prognosis and is characterized by extremely high expression of WEE2 and CCNE1. Comparison of the gene patterns showed that 16 genes expressed were distinctly varied between each cluster. In addition, investigations into the prognostic role of the 16 genes suggested that high expression of ESPL1 and MCM5 were significantly correlated with favorable outcomes. Moreover, we detected that ESPL1 and MCM5 gene expression were negatively correlated with GAC pathologic stage progression.

Conclusions

This study revealed a gene expression pattern of the cell cycle in different GAC subgroups, and suggested individual genes were associated with the clinical outcome and AJCC stages. These results suggest a novel prognostic strategy for GAC and provide information for patient stratification and trials of targeted therapies.

Electronic supplementary material

The online version of this article (10.1186/s12876-018-0811-1) contains supplementary material, which is available to authorized users.

Conservation of the separase regulatory domain

ᅟ: We report a protein sequence analysis of the cell cycle regulatory protease, separase. The sequence and structural conservation of the C-terminal protease domain has long been recognized, whereas the N-terminal regulatory domain of separase was reported to lack detectable sequence similarity. Here we reveal significant sequence conservation of the separase regulatory domain and report a discovery of a cysteine motif (CxCxxC) conserved in major lineages of Metazoa including nematodes and vertebrates. This motif is found in a solvent exposed linker region connecting two TPR-like helical motifs. Mutation of this motif in Caenorhabditis elegans separase leads to a temperature sensitive hypomorphic protein. Conservation of this motif in organisms ranging from C. elegans to humans suggests its functional importance.

REVIEWERS

This article was reviewed by Lakshminarayan Iyer and Michael Galperin.

Increased separase activity and occurrence of centrosome aberrations concur with transformation of MDS

ESPL1/separase, a cysteine endopeptidase, is a key player in centrosome duplication and mitotic sister chromatid separation. Aberrant expression and/or altered separase proteolytic activity are associated with centrosome amplification, aneuploidy, tumorigenesis and disease progression. Since centrosome alterations are a common and early detectable feature in patients with myelodysplastic syndrome (MDS) and cytogenetic aberrations play an important role in disease risk stratification, we examined separase activity on single cell level in 67 bone marrow samples obtained from patients with MDS, secondary acute myeloid leukemia (sAML), de novo acute myeloid leukemia (AML) and healthy controls by a flow cytometric separase activity assay. The separase activity distribution (SAD) value, a calculated measure for the occurrence of cells with prominent separase activity within the analyzed sample, was tested for correlation with the centrosome, karyotype and gene mutation status. We found higher SAD values in bone marrow cells of sAML patients than in corresponding cells of MDS patients. This concurred with an increased incidence of aberrant centrosome phenotypes in sAML vs. MDS samples. No correlation was found between SAD values and the karyotype/gene mutation status. During follow-up of four MDS patients we observed increasing SAD values after transformation to sAML, in two patients SAD values decreased during azacitidine therapy. Cell culture experiments employing MDS-L cells as an in vitro model of MDS revealed that treatment with rigosertib, a PLK1 inhibitor and therapeutic drug known to induce G2/M arrest, results in decreased SAD values. In conclusion, the appearance of cells with unusual high separase activity levels, as indicated by increased SAD values, concurs with the transformation of MDS to sAML and may reflect separase dysregulation potentially contributing to clonal evolution during MDS progression. Separase activity measurement may therefore be useful as a novel additional molecular marker for disease monitoring.