Centromere/kinetochore is assembled through CENP-C oligomerization

Kinetochore is an essential protein complex required for accurate chromosome segregation. The constitutive centromere-associated network (CCAN), a subcomplex of the kinetochore, associates with centromeric chromatin and provides a platform for the kinetochore assembly. The CCAN protein CENP-C is thought to be a central hub for the centromere/kinetochore organization. However, the role of CENP-C in CCAN assembly needs to be elucidated. Here, we demonstrate that both the CCAN-binding domain and the C-terminal region that includes the Cupin domain of CENP-C are necessary and sufficient for chicken CENP-C function. Structural and biochemical analyses reveal self-oligomerization of the Cupin domains of chicken and human CENP-C. We find that the CENP-C Cupin domain oligomerization is vital for CENP-C function, centromeric localization of CCAN, and centromeric chromatin organization. These results suggest that CENP-C facilitates the centromere/kinetochore assembly through its oligomerization.

Transarterial ethiodised oil marking before CT-guided renal cryoablation: evaluation of tumour visibility in various renal cell carcinoma subtypes

AIM

To evaluate ethiodised oil retention of transarterial embolisation using ethiodised oil (ethiodised oil marking) before computed tomography (CT)-guided percutaneous cryoablation (PCA) according to renal cell carcinoma (RCC) subtype.

MATERIALS AND METHODS

Ethiodised oil marking was performed 1-3 days before PCA in 99 patients with 99 RCCs from 2016 to 2020. Ethiodised oil retention on CT images was evaluated retrospectively and CT attenuation values in the tumour were measured. Regions of interest (ROI) were placed on the tumours to calculate: average (ROI-average), maximal (ROI-max), minimum (ROI-min), and standard deviation (ROI-SD). Qualitative scores comprising a five-point scale (5, excellent; 1, poor) were evaluated for the retention scores (RS) of ethiodised oil in the tumour (ethiodised oil-RS) and the visualisation scores (VS) of the boundary between the tumour and renal parenchyma (boundary-VS).

RESULTS

The histological subtypes comprised clear cell (ccRCC; n=85), papillary (pRCC; n=6), and chromophobe/oncocytoma renal cell carcinoma (chrRCC; n=8). The mean ROI-average, ROI-max, and ROI-SD were significantly higher in ccRCCs than in chrRCCs and pRCCs (p<0.05). The mean ethiodised oil-RS was significantly lower in pRCCs than in ccRCCs (p=0.039), and the mean boundary-VS was >4 in all subtypes. Even with poor intratumour ethiodised oil retention (n=6), sufficient boundary-VS was obtained due to "inverted marking." All PCA procedures were completed without additional intravenous contrast material injection at the time of PCA.

CONCLUSION

Regardless of the tumour subtypes, ethiodised oil marking aids in visualising the boundary between the tumour and parenchyma on non-contrast CT in PCA.

Current Strategy to Treat Immunogenic Gastrointestinal Cancers: Perspectives for a New Era

Since pembrolizumab, an anti-programmed death-1 (PD-1) antibody, showed a dramatic response to immunogenic cancers with microsatellite instability-high (MSI-H) and/or deficient mismatch repair (dMMR) in the pilot clinical trial KEYNOTE-016, subsequent studies have confirmed durable responses of anti-PD-1 inhibitors for MSI-H/dMMR solid tumors. As immunotherapy is described as a "game changer," the therapeutic landscape for MSI-H/dMMR solid tumors including gastrointestinal cancers has changed considerably in the last decade. An MSI/MMR status has been established as the predictive biomarker for immune checkpoint blockades, playing an indispensable role in the clinical practice of patients with MSI-H/dMMR tumors. Immunotherapy is also now investigated for locally advanced MSI-H/dMMR gastrointestinal cancers. Despite this great success, a few populations with MSI-H/dMMR gastrointestinal cancers do not respond to immunotherapy, possibly due to the existence of intrinsic or acquired resistance mechanisms. Clarifying the underlying mechanisms of resistance remains a future task, whereas attempts to overcome resistance and improve the efficacy of immunotherapy are currently ongoing. Herein, we review recent clinical trials with special attention to MSI-H/dMMR gastrointestinal cancers together with basic/translational findings, which provide their rationale, and discuss perspectives for the further therapeutic development of treatment in this field.

Chromosome arm length, and a species-specific determinant, define chromosome arm width

Mitotic chromosomes in different organisms adopt various dimensions. What defines these dimensions is scarcely understood. Here, we compare mitotic chromosomes in budding and fission yeasts harboring similarly sized genomes distributed among 16 or 3 chromosomes, respectively. Hi-C analyses and superresolution microscopy reveal that budding yeast chromosomes are characterized by shorter-ranging mitotic chromatin contacts and are thinner compared with the thicker fission yeast chromosomes that contain longer-ranging mitotic contacts. These distinctions persist even after budding yeast chromosomes are fused to form three fission-yeast-length entities, revealing a species-specific organizing principle. Species-specific widths correlate with the known binding site intervals of the chromosomal condensin complex. Unexpectedly, within each species, we find that longer chromosome arms are always thicker and harbor longer-ranging contacts, a trend that we also observe with human chromosomes. Arm length as a chromosome width determinant informs mitotic chromosome formation models.

Autocleavage of separase suppresses its premature activation by promoting binding to cyclin B1

Accurate chromosome segregation requires timely activation of separase, a protease that cleaves cohesin during the metaphase-to-anaphase transition. However, the mechanism that maintains the inactivity of separase prior to this event remains unclear. We provide evidence that separase autocleavage plays an essential role in this process. We show that the inhibition of separase autocleavage results in premature activity before the onset of anaphase, accompanied by the formation of chromosomal bridges and spindle rocking. This deregulation is attributed to the reduced binding of cyclin B1 to separase that occurs during the metaphase-to-anaphase transition. Furthermore, when separase is mutated to render the regulation by cyclin B1 irrelevant, which keeps separase in securin-binding form, the deregulation induced by autocleavage inhibition is rescued. Our results reveal a physiological role of separase autocleavage in regulating separase, which ensures faithful chromosome segregation.

Profiling chromosomal-level variations in gastric malignancies

Aneuploidy arises from persistent chromosome segregation errors, or chromosomal instability. Although it has long been known as a hallmark of cancer cells, reduced cellular fitness upon induced ploidy alterations hinders the understanding of how aneuploidy relates to cancer development in the body. In this study, we employed the fluorescence in situ hybridization (FISH) analysis targeting centromeres to indicate ploidy changes, and quantitatively evaluated the ploidy statuses of gastric tumors derived from a total of 214 patients, ranging from early to advanced diseases. We found that cancer cells reveal a marked elevation of aneuploid population, increasingly in cases diagnosed in advanced stages. The expansion of aneuploid population is well associated with p53 deficiency, consistent with its essential role in genome maintenance. Comparisons among multiple locations within the tumor, or between the primary and metastatic tumors, indicated that cancer cells mostly remain their ploidy alterations throughout the primary tumors, but metastatic tumors may be consisted of cells with either increased or decreased levels of aneuploidy. We also found that a notable proportion of polyploid cells are often present already in chronic gastritis epithelia. These observations underscore that the chromosome-level variations are widespread in gastric cancers, shaping their genetic heterogeneity and malignant properties.

Gender differences in self-perceived changes among Japanese workers with depression

BACKGROUND

The number of patients living with depression continues to increase in Japan. The economic effects of depression include loss of productivity due to both absenteeism and presenteeism. Gender differences have been reported in prevalence, onset pathways and subjective symptoms of depression.

AIMS

To understand how workers with major depressive disorder (MDD) perceive problems in the workplace and examine gender differences in their self-perceived levels of functioning at work, noticed during the initial stages of depression.

METHODS

This is a cross-sectional study of Japanese workers with MDD. Participants' self-perceived changes in the level of functioning at work were surveyed after the diagnosis during the first visit. The relationship between gender and changes in the level of functioning at work as initially perceived by the participants themselves was analysed using the chi-square test, supplemented by a residual analysis.

RESULTS

We administered the survey to 147 workers with MDD. In terms of gender differences in initial self-perceived changes in the level of functioning at work, the proportion of men reporting reduced work efficiency was significantly higher than that of women, while the proportion of women reporting deterioration in relationships with colleagues and superiors was significantly higher than that of men.

CONCLUSIONS

The findings suggest that greater attention to reduced work efficiency by men and to deterioration in work relationships by women with MDD should be essential components of self-care. Managers need to pay attention to the level of functioning and provide adequate social support for employees.

Functional analysis of LAT3 in prostate cancer: Its downstream target and relationship with androgen receptor

L‐type amino acid transporter 3 (LAT3, SLC43A1) is abundantly expressed in prostate cancer (PC) and is thought to play an essential role in PC progression through the cellular uptake of essential amino acids. Here, we analyzed the expression, function, and downstream target of LAT3 in PC. LAT3 was highly expressed in PC cells expressing androgen receptor (AR), and its expression was increased by dihydrotestosterone treatment and decreased by bicalutamide treatment. In chromatin immunoprecipitation sequencing of AR, binding of AR to the SLC43A1 region was increased by dihydrotestosterone stimulation. Knockdown of LAT3 inhibited cell proliferation, migration, and invasion, and the phosphorylation of p70S6K and 4EBP‐1. Separase (ESPL1) was identified as a downstream target of LAT3 by RNA sequencing analysis. In addition, immunostaining of prostatectomy specimens was performed. In the multivariate analysis, high expression of LAT3 was an independent prognostic factor for recurrence‐free survival (hazard ratio: 3.24; P = .0018). High LAT3 expression was correlated with the pathological T stage and a high International Society of Urological Pathology grade. In summary, our results suggest that LAT3 plays an important role in the progression of PC.

Unraveling pathologies underlying chromosomal instability in cancers

Aneuploidy is a widespread feature of malignant tumors that arises through persistent chromosome mis‐segregation in mitosis associated with a pathological condition called chromosomal instability, or CIN. Since CIN is known to have a causal relationship with poor prognosis accompanying by multi‐drug resistance, tumor relapse, and metastasis, many research groups have endeavored to understand the mechanisms underlying CIN. In this review, we overview possible etiologies of CIN. The key processes to achieve faithful chromosome segregation include the regulation of sister chromatid cohesion, kinetochore‐microtubule attachment, bipolar spindle formation, spindle‐assembly checkpoint, and the activity of separase. Aberrant chromosome structures during DNA replication might also be a potential cause of CIN. Defective regulation in these processes can lead to chromosome mis‐segregation, manifested by lagging chromosomes, and DNA bridges in anaphase, leading to gross chromosome rearrangements. Investigation into the molecular etiologies of CIN should allow us to explore novel strategies to intervene in CIN to control cancers.

Kinetochore stretching-mediated rapid silencing of the spindle-assembly checkpoint required for failsafe chromosome segregation

The spindle-assembly checkpoint facilitates mitotic fidelity by delaying anaphase onset in response to microtubule vacancy at kinetochores. Following microtubule attachment, kinetochores receive microtubule-derived force, which causes kinetochores to undergo repetitive cycles of deformation; this phenomenon is referred to as kinetochore stretching. The nature of the forces and the relevance relating this deformation are not well understood. Here, we show that kinetochore stretching occurs within a framework of single end-on attached kinetochores, irrespective of microtubule poleward pulling force. An experimental method to conditionally interfere with the stretching allowed us to determine that kinetochore stretching comprises an essential process of checkpoint silencing by promoting PP1 phosphatase recruitment after the establishment of end-on attachments and removal of the majority of checkpoint-activating kinase Mps1 from kinetochores. Remarkably, we found that a lower frequency of kinetochore stretching largely correlates with a prolonged metaphase in cancer cell lines with chromosomal instability. Perturbation of kinetochore stretching and checkpoint silencing in chromosomally stable cells produced anaphase bridges, which can be alleviated by reducing chromosome-loaded cohesin. These observations indicate that kinetochore stretching-mediated checkpoint silencing provides an unanticipated etiology underlying chromosomal instability and underscores the importance of a rapid metaphase-to-anaphase transition in sustaining mitotic fidelity.

Pathogenicity assessment of variants for breast cancer susceptibility genes based on BRCAness of tumor sample

Genes involved in the homologous recombination repair pathway—as exemplified by BRCA1, BRCA2, PALB2, ATM, and CHEK2—are frequently associated with hereditary breast and ovarian cancer syndrome. Germline mutations in the loci of these genes with loss of heterozygosity or additional somatic truncation at the WT allele lead to the development of breast cancers with characteristic clinicopathological features and prominent genomic features of homologous recombination deficiency, otherwise referred to as “BRCAness.” Although clinical genetic testing for these and other genes has increased the chances of identifying pathogenic variants, there has also been an increase in the prevalence of variants of uncertain significance, which poses a challenge to patient care because of the difficulties associated with making further clinical decisions. To overcome this challenge, we sought to develop a methodology to reclassify the pathogenicity of these unknown variants using statistical modeling of BRCAness. The model was developed with Lasso logistic regression by comparing 116 genomic attributes derived from 37 BRCA1/2 biallelic mutant and 32 homologous recombination‐quiescent breast cancer exomes. The model showed 95.8% and 86.7% accuracies in the training cohort and The Cancer Genome Atlas validation cohort, respectively. Through application of the model for variant reclassification of homologous recombination‐associated hereditary breast and ovarian cancer causal genes and further assessment with clinicopathological features, we finally identified one likely pathogenic and five likely benign variants. As such, the BRCAness model developed from the tumor exome was robust and provided a reasonable basis for variant reclassification.

Prolonged mitosis causes separase deregulation and chromosome nondisjunction

During mitotic chromosome segregation, the protease separase severs cohesin between sister chromatids. A probe for separase activity has shown that separase undergoes abrupt activation shortly before anaphase onset, after being suppressed throughout metaphase; however, the relevance of this control remains unclear. Here, we report that separase activates precociously, with respect to anaphase onset, during prolonged metaphase in multiple types of cancer cell lines. The artificial extension of metaphase in chromosomally stable diploid cells leads to precocious activation and, subsequently, to chromosomal bridges in anaphase, which seems to be attributable to incomplete cohesin removal. Conversely, shortening back of a prolonged metaphase restores the activation of separase and ameliorates anaphase bridge formation. These observations suggest that retarded metaphase progression affects the separase activation profile and its enzymatic proficiency. Our findings provide an unanticipated etiology for chromosomal instability in cancers and underscore the relevance of swift mitotic transitions for fail-safe chromosome segregation.

CBMS-05 Biological and Pathological meaning of aneuploidy in mouse glioma stem sell

Chromosomal instability (CIN) is a pathological condition where cells continuously mis-segregate chromosomes, producing aneuploid cells. CIN has been recognized as a hallmark of cancer, and its correlation with biological malignancy has been pointed out. Glioma cell line often reveals karyotype aberrations, and a variety of ploidy in the tumor tissue. However, several studies have indicated that aneuploidy is disadvantageous for proliferation or tumorigenesis, and these paradox prompt us to address the role of aneuploid cells in tumor specimens. Here, we adopted mouse glioma stem cell lineages and found that aneuploid population is increased in glioma stem cells in vitro. We also examined Aurora B at centromeres which is crucial for failsafe chromosome segregation and found its reduced activity in glioma stem cells, suggesting that insufficient Aurora B activity plays a causative role in CIN in glioma stem cells. Next, to investigate the tumorigenicity of aneuploid cells, we sorted the glioma stem cells depending on the karyotype pattern, and allografted into mouse brain. We found that the growth rate of diploid glioma stem cells was higher than others in vitro, and the probability of survival after allogeneic transplant was significantly lower in diploid groups. We will discuss the role of ploidy in glioma cells populations.

BRAF Mutation in Colorectal Cancers: From Prognostic Marker to Targetable Mutation

Simple Summary

Colorectal cancer with a mutation in an oncogene BRAF has paid much attention, as it comprises a population with dismal prognosis since two decades ago. A series of research since then has successfully changed this malignancy to be treatable with specific treatment. Here we thoroughly overviewed the basic, translational and clinical studies on colorectal cancer with BRAF mutation from a physician’s viewpoint. Accumulating lines of evidence suggest that intervention of the trunk cellular growth signal transduction pathway, namely EGFR-RAS-RAF-MEK-ERK pathway, is a clue to controlling this disease. However, it is not so straightforward. Recent studies unveil the diverse and plastic nature of this signal transduction pathway. We will introduce our endeavor to conquer this condition, based on newly arriving datasets, and discuss how we could open the door to future development of CRC treatment.

Abstract

The Raf murine sarcoma viral oncogene homolog B (BRAF) mutation is detected in 8–12% of metastatic colorectal cancers (mCRCs) and is strongly correlated with poor prognosis. The recent success of the BEACON CRC study and the development of targeted therapy have led to the determination of BRAF-mutated mCRCs as an independent category. For nearly two decades, a growing body of evidence has established the significance of the BRAF mutation in the development of CRC. Herein, we overview both basic and clinical data relevant to BRAF-mutated CRC, mainly focusing on the development of treatment strategies. This review is organized into eight sections, including clinicopathological features, molecular features, prognosis, the predictive value of anti-epidermal growth factor receptor (EGFR) therapy, resistant mechanisms for BRAF-targeting treatment, the heterogeneity of the BRAF mutation, future perspectives, and conclusions. A characterization of the canonical mitogen-activated protein kinase (MAPK) pathway is essential for controlling this malignancy, and the optimal combination of multiple interventions for treatments remains a point of debate.

High sensitivity cardiac troponin T is a useful biomarker for predicting prognosis of the patients with sarcoidosis

Background

Cardiac involvement is one of the most significant prognostic factors for the patients with sarcoidosis. In spite of the advancement of diagnostic tools, such as cardiac magnetic resonance imaging or 18F-fluoro-2-deoxyglucose positron emission tomography, there is still significant room for improvement in cardiac screening and prognostic prediction.

Purpose

To evaluate the prognostic factors for the patients with sarcoidosis.

Methods and results

We prospectively studied 133 patients with sarcoidosis and evaluated clinical data including biomarkers. The mean age at diagnosis was 62.1±12.8 years. During a mean follow up period of 5.6±4.1 years, nine patients died and 27 patients suffered from cardiac events (cardiac death, heart failure admission, arrhythmic event). We divided patients into two groups according to cardiac events, event group had high serum high-sensitivity cardiac troponin T (hs-cTnT) (0.028±0.017 vs. 0.015±0.011 ng/ml, p&lt;0.001), high BNP (409.2±634.0 vs. 122.4±195.8 pg/ml, p&lt;0.001), low EF (43.1±16.4 vs. 59.2±15.5%, p&lt;0.001). This was observed even if those patients were not diagnosed with cardiac involvement at the enrollment. On the other hand, there were no significant differences in the values of angiotensin-converting enzyme, lysozyme, soluble interleukin-2 receptor, or calcium in both groups. Multivariate analysis revealed that hs-cTnT was an independent biomarker to predict cardiac events (hs-cTnT &gt;0.014 ng/ml: HR 3.2, 95% CI 1.02 to 10.19, p=0.046).

Conclusion

Hs-cTnT was a useful biomarker for predicting cardiac events for the patients with sarcoidosis even if cardiac involvement was not detected at initial evaluation.

Figure 1

Funding Acknowledgement

Type of funding source: None

Prognostic impact of atrial fibrillation in patients with hypertrophic cardiomyopathy in a community-based Japanese cohort: results from Kochi RYOMA study

Background

The prognostic impact of atrial fibrillation (AF) in patients with hypertrophic cardiomyopathy (HCM) is not fully elucidated.

Purpose

The aim of this study was to examine the prevalence and prognostic impact of AF in a prospectively assembled community-based HCM patient cohort in an aged Japanese community.

Methods

In 2004, we established a cardiomyopathy registration network in Kochi Prefecture, Japan, consisting of 9 hospitals, and finally 293 patients with HCM were followed.

Results

The ages at registration and at diagnosis were 63±14 and 56±16 years, respectively, and 197 patients (67%) were men. 86 patients (29%) showed AF. During follow-up period of 6.1±3.2 years, 44 patients died. In those patients, HCM-related deaths occurred in 23 patients with an annual mortality rate of 1.3%. Regarding HCM-related adverse events including HCM-related deaths, appropriate ICD discharge, heart failure admission and hospitalization for embolic events, a total of 77 cardiovascular events in 70 patients occurred. Multivariate analysis revealed that presence of AF, left ventricular (LV) outflow obstruction, NYHA functional class III, and lower LV fractional shortening at registration were significant predictors of these adverse events. During the follow-up period, additional 31 patients (11%) developed new-onset AF. Importantly, the incidence of HCM-related adverse events was significantly higher in patients with new AF observed from its onset compared with those with AF at registration (log-rank p=0.029) (Figure 1).

Conclusions

In an unselected HCM registry in an aged Japanese community, presence of AF, particularly new-onset AF, was associated with unfavorable clinical outcomes. AF is not just a marker of the disease stage but an important trigger of HCM-related adverse events.

Figure 1

Funding Acknowledgement

Type of funding source: None

Identification of a novel nucleolar protein complex required for mitotic chromosome segregation through centromeric accumulation of Aurora B

The nucleolus is a membrane-less nuclear structure that disassembles when cells undergo mitosis. During mitosis, nucleolar factors are thus released from the nucleolus and dynamically change their subcellular localization; however, their functions remain largely uncharacterised. Here, we found that a nucleolar factor called nucleolar protein 11 (NOL11) forms a protein complex with two tryptophan-aspartic acid (WD) repeat proteins named WD-repeat protein 43 (WDR43) and Cirhin in mitotic cells. This complex, referred to here as the NWC (NOL11-WDR43-Cirhin) complex, exists in nucleoli during interphase and translocates to the periphery of mitotic chromosomes, i.e., perichromosomal regions. During mitotic progression, both the congression of chromosomes to the metaphase plate and sister chromatid cohesion are impaired in the absence of the NWC complex, as it is required for the centromeric enrichment of Aurora B and the associating phosphorylation of histone H3 at threonine 3. These results reveal the characteristics of a novel protein complex consisting of nucleolar proteins, which is required for regulating kinetochores and centromeres to ensure faithful chromosome segregation.

Nuclear microenvironment in cancer: Control through liquid-liquid phase separation

The eukaryotic nucleus is not a homogenous single‐spaced but a highly compartmentalized organelle, partitioned by various types of membraneless structures, including nucleoli, PML bodies, paraspeckles, DNA damage foci and RNA clouds. Over the past few decades, these nuclear structures have been implicated in biological reactions such as gene regulation and DNA damage response and repair, and are thought to provide “microenvironments,” facilitating these reactions in the nucleus. Notably, an altered morphology of these nuclear structures is found in many cancers, which may relate to so‐called “nuclear atypia” in histological examinations. While the diagnostic significance of nuclear atypia has been established, its nature has remained largely enigmatic and awaits characterization. Here, we review the emerging biophysical principles that govern biomolecular condensate assembly in the nucleus, namely, liquid‐liquid phase separation (LLPS), to investigate the nature of the nuclear microenvironment. In the nucleus, LLPS is typically driven by multivalent interactions between proteins with intrinsically disordered regions, and is also facilitated by protein interaction with nucleic acids, including nuclear non–coding RNAs. Importantly, an altered LLPS leads to dysregulation of nuclear events and epigenetics, and often to tumorigenesis and tumor progression. We further note the possibility that LLPS could represent a new therapeutic target for cancer intervention.

Kinase inhibition profiles as a tool to identify kinases for specific phosphorylation sites

There are thousands of known cellular phosphorylation sites, but the paucity of ways to identify kinases for particular phosphorylation events remains a major roadblock for understanding kinase signaling. To address this, we here develop a generally applicable method that exploits the large number of kinase inhibitors that have been profiled on near-kinome-wide panels of protein kinases. The inhibition profile for each kinase provides a fingerprint that allows identification of unknown kinases acting on target phosphosites in cell extracts. We validate the method on diverse known kinase-phosphosite pairs, including histone kinases, EGFR autophosphorylation, and Integrin β1 phosphorylation by Src-family kinases. We also use our approach to identify the previously unknown kinases responsible for phosphorylation of INCENP at a site within a commonly phosphorylated motif in mitosis (a non-canonical target of Cyclin B-Cdk1), and of BCL9L at S915 (PKA). We show that the method has clear advantages over in silico and genetic screening.

Determination of Neutral Lactase Activity in Industrial Enzyme Preparations by a Colorimetric Enzymatic Method: Collaborative Study

Thirteen laboratories participated in a collaborative study to validate a colorimetric assay for determining neutral lactase activity in industrial enzyme preparations. Each laboratory received 5 duplicate samples with activity levels of 2000 and 5000 neutral lactase units provided by 4 commercial suppliers. Two laboratories did not return results. Method performance was calculated according to AOAC guidelines. From the 11 remaining laboratories, 3 were excluded from statistical analysis because of invalid data determined during initial review by Youden pair, value versus laboratory. Repeatability relative standard deviation (RSDr) values ranged from 3.20 to 8.62%, and reproducibility relative standard deviation (RSDR) values ranged from 8.77 to 16.35%. With outliers excluded, RSDr values ranged from 2.94 to 5.01%, and RSDRvalues ranged from 7.50 to 13.84%. The colorimetric enzymatic method for determining neutral lactase activity in industrial enzyme preparations has been adopted first action by AOAC INTERNATIONAL.

Enrichment of CLDN18-ARHGAP fusion gene in gastric cancers in young adults

Gastric cancer in young adults has been pointed out to comprise a subgroup associated with distinctive clinicopathological features, including an equal gender distribution, advanced disease, and diffuse‐type histology. Comprehensive molecular analyses of gastric cancers have led to molecular‐based classifications and to specific and effective treatment options. The molecular traits of gastric cancers in young adults await investigations, which should provide a clue to explore therapeutic strategies. Here, we studied 146 gastric cancer patients diagnosed at the age of 40 years or younger at the Cancer Institute Hospital (Tokyo, Japan). Tumor specimens were examined for Helicobacter pylori infection, Epstein‐Barr virus positivity, and for the expression of mismatch repair genes to indicate microsatellite instability. Overexpression, gene amplifications, and rearrangements of 18 candidate driver genes were examined by immunohistochemistry and FISH. Although only a small number of cases were positive for Epstein‐Barr virus and microsatellite instability (n = 2 each), we repeatedly found tumors with gene fusion between a tight‐junction protein claudin, CLDN18, and a regulator of small G proteins, ARHGAP, in as many as 22 cases (15.1%), and RNA sequencing identified 2 novel types of the fusion. Notably, patients with the CLDN18‐ARHGAP fusion revealed associations between aggressive disease and poor prognosis, even when grouped by their clinical stage. These observations indicate that a fusion gene between CLDN18 and ARHGAP is enriched in younger age‐onset gastric cancers, and its presence could contribute to their aggressive characteristics.

Folding the genome into mitotic chromosomes

How linear DNA molecules are packaged into compact cylindrical chromosomes in preparation for cell division has remained one of the central outstanding questions in cell biology. Condensin is a highly conserved protein complex that universally determines large-scale DNA geometry during mitotic chromosome assembly. A wide range of recently developed approaches, including super resolution microscopy, single molecule imaging, Hi-C analyses and computational modeling, have profoundly changed how we view mitotic chromosomes. This review highlights recent discoveries on chromosome architecture and condensin function.

Quantitative analyses of the metaphase-to-anaphase transition reveal differential kinetic regulation for securin and cyclin B1

Separation of sister chromatids is a drastic and irreversible step in the cell cycle. The key biochemistry behind this event is the proteolysis mediated by the ubiquitin ligase called the anaphase promoting complex, or APC/C. Securin and cyclin B1 are the two established substrates for APC/C whose degradation releases separase and inactivates cyclin B1-dependent kinase 1 (cdk1), respectively, at the metaphase-to-anaphase transition. In this study, we have combined biochemical quantifications with mathematical simulations to characterize the kinetic regulation of securin and cyclin B1, in the cytoplasmic and chromosomal compartments, and found that they are differentially distributed and degraded with different rates. Modeling their interaction with separase predicted that activation timing of separase well coincides with the decline of securin-separase concentration in the cytoplasm. Notably, it also coincides with the peak of cyclin B1-separase level on chromosomes, which appeared crucial to coordinate the timing for separase activation and cdk1 inhibition. We have also conducted phosphoproteomic analysis and identified Ki67 as a chromosomal cdk1 substrate whose dephosphorylation is facilitated by cyclin B1-separase interaction in anaphase.

Dynamics of sister chromatids through the cell cycle: Together and apart

Takahashi and Hirota preview work from Stanyte et al. examining the behavior of sister chromatids and their resolution as the cell cycle progresses.

When and how sister chromatid resolution occurs after DNA replication is a fundamental question. Stanyte et al. (2018. J. Cell Biol.https://doi.org/10.1083/jcb.201801157) used CRISPR/Cas9 technology to label and track genomic loci in live cells throughout the cell cycle, shedding light on how replication is linked to mitotic sister chromatid organization.

Nucleolar integrity during interphase supports faithful Cdk1 activation and mitotic entry

The nucleolus is a dynamic nuclear body that has been demonstrated to disassemble at the onset of mitosis; the relationship between cell cycle progression and nucleolar integrity, however, remains poorly understood. We studied the role of nucleolar proteins in mitosis by performing a global analysis using small interfering RNAs specific to nucleolar proteins; we focused on nucleolar protein 11 (NOL11), with currently unknown mitotic functions. Depletion of NOL11 delayed entry into the mitotic phase owing to increased inhibitory phosphorylation of cyclin-dependent kinase 1 (Cdk1) and aberrant accumulation of Wee1, a kinase that phosphorylates and inhibits Cdk1. In addition to effects on overall mitotic phenotypes, NOL11 depletion reduced ribosomal RNA (rRNA) levels and caused nucleolar disruption during interphase. Notably, mitotic phenotypes found in NOL11-depleted cells were recapitulated when nucleolar disruption was induced by depletion of rRNA transcription factors or treatment with actinomycin D. Furthermore, delayed entry into the mitotic phase, caused by the depletion of pre-rRNA transcription factors, was attributable to nucleolar disruption rather than to G₂/M checkpoint activation or reduced protein synthesis. Our findings therefore suggest that maintenance of nucleolar integrity during interphase is essential for proper cell cycle progression to mitosis via the regulation of Wee1 and Cdk1.

cDNA microarray analysis identifies NR4A2 as a novel molecule involved in the pathogenesis of Sjögren's syndrome

To examine genes expressed specifically in labial salivary glands (LSGs) of patients with Sjögren's syndrome (SS) in comparison with those of patients with immunoglobulin (Ig)G4-related disease (IgG4-RD), and to identify the genes involved in the pathogenesis of SS. Gene expression in LSGs of SS patients, IgG4-RD patients and healthy controls (HC) was analysed by cDNA microarray. Quantitative polymerase chain reaction (qPCR) was used to validate the up-regulation of differentially expressed genes (DEGs) in SS. Protein production of the validated gene in LSGs was examined by immunofluorescence (IF) assay. The association of molecular functions of the gene with the pathological conditions in SS was examined using peripheral blood lymphocytes. Among 1320 DEGs up-regulated in SS, qPCR confirmed the up-regulation of NR4A2 in LSGs of SS compared with IgG4-RD. IF staining showed higher production of NR4A2 in nuclei of CD4⁺ T cells and interleukin (IL)-17-producing cells in LSGs of SS, compared with IgG4-RD. Over-expression of NR4A2 mRNA was observed in peripheral CD4⁺ T cells of SS patients, compared with HC. Nuclear NR4A2 expression in T helper type 17 (Th17)-polarized CD4⁺ T cells determined by cellular IF was significantly higher in SS than in HC. Importazole, an inhibitor of importin-β, inhibited nuclear transport of NR4A2 and Th17 polarization along with IL-21 expression in naive CD4⁺ T cells under Th17-polarizing conditions, but did not alter retinoic acid receptor-related orphan receptor C (RORC) expression. NR4A2 seems to promote Th17 polarization via increased expression and intranuclear localization in CD4⁺ T cells of SS patients, which could play a critical role in the pathogenesis of SS.

IL4Rα and ADAM33 as genetic markers in asthma exacerbations and type-2 inflammatory endotype

BACKGROUND

Genetic markers of susceptibility to asthma exacerbations in adults remain unclear.

OBJECTIVE

To identify genetic markers of asthma exacerbations, particularly in patients with type-2 inflammatory endotype.

METHODS

In this observational study of patients enrolled in the Kinki Hokuriku Airway disease Conference multicenter study, frequency of exacerbations requiring systemic corticosteroids during 2 years after enrolment and associated risk factors was determined. For genetic marker analysis, interleukin-4 receptor α (IL4RA) rs8832 and a disintegrin and metalloprotease 33 (ADAM33) S_2 (rs528557), T_1 (rs2280091), T_2 (rs2280090), and V_4 (rs2787094) variants were included. Elevated serum periostin levels at enrolment (≥95 ng/mL, defined as type-2 inflammatory endotype) were considered in the analysis.

RESULTS

Among 217 patients who were successfully followed up for 2 years after enrolment, 60 patients showed at least one asthma exacerbation during the 2 years. Airflow limitation (%FEV₁ <80%) and recent exacerbations but not genetic variants were identified as risk markers of exacerbations. A total of 27 patients showed type-2 inflammatory endotype (serum periostin ≥95 ng/mL at enrolment) and subsequent exacerbations; risk factors in these patients were airflow limitation (odds ratio, 6.51; 95% confidence interval (CI): 2.37-18.6; P=.0003), GG genotype of IL4RA rs8832 (odds ratio, 4.01; 95% CI: 1.47-11.0; P=.007), and A allele of ADAM33 T_2 (odds ratio, 2.81; 95% CI: 1.05-7.67; P=.04) by multivariate analysis. In addition, GG genotype of IL4RA rs8832 was associated with type-2 endotype, whereas A allele of ADAM33 T_2 was associated with mixed type of eosinophilic/type-2 and neutrophilic inflammations.

CONCLUSIONS AND CLINICAL RELEVANCE

IL4RA and ADAM33 variants may be risk markers of asthma exacerbations in type-2 inflammatory endotype. Precise endotyping may facilitate the identification of genetic risk markers of asthma exacerbations.

Phosphoproteomic analysis of human mitotic chromosomes identified a chromokinesin KIF4A

Protein phosphorylation is the prime post-translational modification to drive cell division. Identification of phosphorylated proteins and their related kinases has uncovered molecular networks underlying mitotic processes, including chromosome assembly. Here we aimed to identify phosphoproteins from a mitotic chromosome-enriched lysate biochemically using mass spectrometry. We employed the Polo-box domain (PBD) of Polo-like kinase to tether phosphorylated proteins in the lysate. Resulting candidates included a number of chromosomal proteins that would not be identified unless using chromosome-enriched fractions. Among them, we focused to a chromokinesin KIF4A which becomes concentrated along the longitudinal axis of mitotic condensed chromatids. We found that KIF4A is phosphorylated specifically during mitosis, depending on the activity of Cdk1 and Aurora B, which turned out to be required for KIF4A to interact with condensin I. The molecular link between KIF4A and condensin raises an interesting possibility that the interaction of two distantly related ATPases is triggered by mitotic phosphorylation.

RORγt antagonist suppresses M3 muscarinic acetylcholine receptor-induced Sjögren's syndrome-like sialadenitis

We showed recently that M3 muscarinic acetylcholine receptor (M3R)-reactive CD3⁺ T cells play a pathogenic role in the development of murine autoimmune sialadenitis (MIS), which mimics Sjögren's syndrome (SS). The aim of this study was to determine the effectiveness and mechanism of action of retinoic acid-related orphan receptor-gamma t (RORγt) antagonist (A213) in MIS. Splenocytes from M3R knockout (M3R^-/- ) mice immunized with murine M3R peptide mixture were inoculated into recombination-activating gene 1 knockout (Rag-1^-/- ) mice (M3R^-/- →Rag-1^-/- ) with MIS. Immunized M3R^-/- mice (pretransfer treatment) and M3R^-/- →Rag-1^-/- mice (post-transfer treatment) were treated with A213 every 3 days. Salivary volume, severity of sialadenitis and cytokine production from M3R peptide-stimulated splenocytes and lymph node cells were examined. Effects of A213 on cytokine production were analysed by enzyme-linked immunosorbent assay (ELISA) and on T helper type 1 (Th1), Th17 and Th2 differentiation from CD4⁺ T cells by flow cytometry. Pretransfer A213 treatment maintained salivary volume, improved MIS and reduced interferon (IFN)-γ and interleukin (IL)-17 production significantly compared with phosphate-buffered saline (PBS) (P < 0·05). These suppressive effects involved CD4⁺ T cells rather than CD11c⁺ cells. Post-transfer treatment with A213 increased salivary volume (P < 0·05), suppressed MIS (P < 0·005) and reduced IFN-γ and IL-17 production (P < 0·05). In vitro, A213 suppressed IFN-γ and IL-17 production from M3R-stimulated splenocytes and CD4⁺ T cells of immunized M3R^-/- mice (P < 0·05). In contrast with M3R specific responses, A213 suppressed only IL-17 production from Th17 differentiated CD4⁺ T cells without any effect on Th1 and Th2 differentiation in vitro. Our findings suggested that RORγt antagonism is potentially suitable treatment strategy for SS-like sialadenitis through suppression of IL-17 and IFN-γ production by M3R-specific T cells.

A rare variant in CYP27A1 and its association with atopic dermatitis with high serum total IgE

This study investigated rare variants associated with atopic dermatitis. We performed exome analyses on 37 patients who were diagnosed with atopic dermatitis by board-certified dermatologists and had total serum IgE levels greater than 1000 IU/ml. The exome analysis identified seven variants with <1% allele frequency in Asian (ASN) population of 1000 Genomes Project phase 1 data and >5% allele frequency in the atopic dermatitis exome samples. We then conducted a replication study using 469 atopic dermatitis patients with total serum IgE ≥1000 IU/ml and 935 Japanese controls to assess the presence of these 7 candidate variants. The replication study confirmed that CYP27A1 rs199691576 (A/G) was associated with atopic dermatitis with high serum IgE levels (P = 0.012, odds ratio = 2.1). CYP27A1 is involved in the metabolism of vitamin D3, which plays important roles in modulating immune function. Previous studies have reported polymorphisms in vitamin D pathway genes that are associated with allergy-related phenotypes. Our data confirm the importance of genes regulating the vitamin D pathway in the development of atopic dermatitis.

Condensin I-mediated mitotic chromosome assembly requires association with chromokinesin KIF4A

In this study, Takahashi et al. investigated the role of chromokinesin KIF4A in condensin complexes. They found that KIF4A associates with condensin I but not with condensin II during mitosis, providing new insight into the regulation of condensin I and mitotic chromsome organization.

The chromokinesin KIF4A has been implicated in shaping mitotic chromosomes, but its functional relationship to condensin complexes remains controversial. Here, we found that, in mitosis, KIF4A associates with condensin I but not with condensin II. Mutational analyses indicated that the enrichment of condensin I to chromosomal axes depends on its association with KIF4A in a way that likely involves its motor activity. Remarkably, this interaction is required for condensin I to confer physiological properties to chromosomes. These observations provide an insight into how condensin I is enriched at chromosomal axes and underscore the significance of axial structure in organizing mitotic chromosomes.

Sister chromatid resolution is an intrinsic part of chromosome organization in prophase

The formation of mitotic chromosomes requires both compaction of chromatin and the resolution of replicated sister chromatids. Compaction occurs during mitotic prophase and prometaphase, and in prophase relies on the activity of condensin II complexes. Exactly when and how sister chromatid resolution occurs has been largely unknown, as has its molecular requirements. Here, we established a method to visualize sister resolution by sequential replication labelling with two distinct nucleotide derivatives. Quantitative three-dimensional imaging then allowed us to measure the resolution of sister chromatids throughout mitosis by calculating their non-overlapping volume within the whole chromosome. Unexpectedly, we found that sister chromatid resolution starts already at the beginning of prophase, proceeds concomitantly with chromatin compaction and is largely completed by the end of prophase. Sister chromatid resolution was abolished by inhibition of topoisomerase IIα and by depleting or preventing mitotic activation of condensin II, whereas blocking cohesin dissociation from chromosomes had little effect. Mitotic sister chromatid resolution is thus an intrinsic part of mitotic chromosome formation in prophase that relies largely on DNA decatenation and shares the molecular requirement for condensin II with prophase compaction.

Esco1 Acetylates Cohesin via a Mechanism Different from That of Esco2

Sister chromatid cohesion is mediated by cohesin and is essential for accurate chromosome segregation. The cohesin subunits SMC1, SMC3, and Rad21 form a tripartite ring within which sister chromatids are thought to be entrapped. This event requires the acetylation of SMC3 and the association of sororin with cohesin by the acetyltransferases Esco1 and Esco2 in humans, but the functional mechanisms of these acetyltransferases remain elusive. Here, we showed that Esco1 requires Pds5, a cohesin regulatory subunit bound to Rad21, to form cohesion via SMC3 acetylation and the stabilization of the chromatin association of sororin, whereas Esco2 function was not affected by Pds5 depletion. Consistent with the functional link between Esco1 and Pds5, Pds5 interacted exclusively with Esco1, and this interaction was dependent on a unique and conserved Esco1 domain. Crucially, this interaction was essential for SMC3 acetylation and sister chromatid cohesion. Esco1 localized to cohesin localization sites on chromosomes throughout interphase in a manner that required the Esco1-Pds5 interaction, and it could acetylate SMC3 before and after DNA replication. These results indicate that Esco1 acetylates SMC3 via a mechanism different from that of Esco2. We propose that, by interacting with a unique domain of Esco1, Pds5 recruits Esco1 to chromatin-bound cohesin complexes to form cohesion. Furthermore, Esco1 acetylates SMC3 independently of DNA replication.

Genomewide association study identifies HAS2 as a novel susceptibility gene for adult asthma in a Japanese population

BACKGROUND

It is increasingly clear that asthma is not a single disease, but a disorder with vast heterogeneity in pathogenesis, severity, and treatment response. To date, 30 genomewide association studies (GWASs) of asthma have been performed, including by our group. However, most gene variants identified so far confer relatively small increments in risk and explain only a small proportion of familial clustering.

OBJECTIVE

To identify additional genetic determinants of susceptibility to asthma using a selected Japanese population with reduced tobacco smoking exposure.

METHODS

We performed a GWAS by genotyping a total of 480 098 single-nucleotide polymorphisms (SNPs) for a Japanese cohort consisting of 734 healthy controls and 240 patients with asthma who had smoked for no more than 10 pack-years. The SNP with the strongest association was genotyped in two other independent Japanese cohorts consisting of a total of 531 healthy controls and 418 patients with asthma who had smoked for no more than 10 pack-years. For the hyaluronan synthase 2 (HAS2) gene, we investigated SNP-gene associations using an expression quantitative trait loci (eQTL) database and also analysed its gene expression profiles in 13 different normal tissues.

RESULTS

In the discovery GWAS, a SNP located upstream of HAS2, rs7846389, showed the strongest statistical significance (P = 1.43 × 10(-7) ). In the two independent replication cohorts, rs7846389 was consistently associated with asthma (nominal P = 0.0152 and 0.0478 in the first and second replication cohorts, respectively). In the meta-analysis, association of rs7846389 with susceptibility to asthma reached the level of genomewide significance (P = 7.92 × 10(-9) ). This variant was strongly correlated with HAS2 mRNA expression. The strongest expression of the gene was detected in the lung.

CONCLUSIONS

Our study identified HAS2 as a novel candidate gene for susceptibility to adult asthma.

Clarifying the role of condensin in shaping chromosomes

A major controversy in the field of chromosome research has been whether condensin is required for achieving the highly compacted state of chromatin fibres in mitosis and meiosis. Through genetic experiments in mouse oocytes, condensin is now found to be indispensable for meiotic chromosome assembly by mediating chromosome compaction and disentanglement of sister chromatids and by conferring rigidity to chromosomes.

Predictors of the response to treatment in acute lupus hemophagocytic syndrome

OBJECTIVE

The objective of this paper is to identify predictors for the response to treatment of acute lupus hemophagocytic syndrome (ALHS).

METHODS

We reviewed seven cases with ALHS admitted to our hospital and published ALHS cases identified in the 2001-2014 Medline database, and then conducted univariate and multivariate analyses to identify predictors for the response to treatment.

RESULTS

Review of our cases showed a significant and negative correlation between serum ferritin and anti-DNA antibody (p = 0.0025). All three patients treated with cyclosporine A (CsA) were considered responders despite high serum ferritin and corticosteroid resistance. We also reviewed 93 patients with ALHS identified in 46 articles. Multiple logistic regression analysis identified C-reactive protein (CRP) (OR 0.83, p = 0.042) and hemoglobin (OR 1.53, p = 0.026) measured at diagnosis of ALHS as significant predictors of the response to corticosteroid monotherapy. Moreover, among 32 patients treated with CsA, serum ferritin was significantly higher in CsA responders (12163 ± 16864 µg/l, n = 22) than in non-responders (3456 ± 6267/µg/l, p = 0.020, n = 10). Leukocyte count was significantly lower in the CsA responders (1940.0 ± 972.3/µl) than in the non-responders (3253 ± 2198/µl, p = 0.034).

CONCLUSION

Low CRP and high hemoglobin can predict a positive response to corticosteroid monotherapy while high serum ferritin and low leukocyte count can predict a positive response to CsA in patients with ALHS and therefore, when corticosteroid monotherapy is not effective in such cases, CsA could be the first choice of an additional immunosuppressive agent.

GLCCI1 variant accelerates pulmonary function decline in patients with asthma receiving inhaled corticosteroids

BACKGROUND

In steroid-naive patients with asthma, several gene variants are associated with a short-term response to inhaled corticosteroid (ICS) treatment; this has mostly been observed in Caucasians. However, not many studies have been conducted for other ethnicities. Here, we aimed to determine the relationship between the annual decline in forced expiratory flow volume in one second (FEV1 ) and the variant of the glucocorticoid-induced transcript 1 gene (GLCCI1) in Japanese patients with asthma receiving long-term ICS treatment, taking into account the effect of high serum periostin levels, a known association factor of pulmonary function decline and a marker of refractory eosinophilic/Th2 inflammation.

METHODS

In this study, 224 patients with asthma receiving ICS treatment for at least 4 years were enrolled. The effects of single-nucleotide polymorphisms (SNPs) in GLCCI1, stress-induced phosphoprotein 1 (STIP1), and T gene on the decline in FEV1 of 30 ml/year or greater were determined.

RESULTS

Besides the known contributing factors, that is, the most intensive treatment step, ex-smoking, and high serum periostin levels (≥95 ng/ml), the GG genotype of GLCCI1 rs37973, and not other SNPs, was independently associated with a decline in FEV1 of 30 ml/year or greater. When patients were stratified according to their serum periostin levels, the GG genotype of rs37973 was significantly associated with blood eosinophilia (≥250/μl) in the high serum periostin group.

CONCLUSIONS

A GLCCI1 variant is a risk factor of pulmonary function decline in Japanese patients with asthma receiving long-term ICS treatment. Thus, GLCCI1 may be associated with response to ICS across ethnicities.

NFBD1/MDC1 is phosphorylated by PLK1 and controls G2/M transition through the regulation of a TOPOIIα-mediated decatenation checkpoint

Although it has been established that nuclear factor with BRCT domain 1/ mediator of the DNA damage checkpoint protein 1 (NFBD1/MDC1) is closely involved in DNA damage response, its possible contribution to the regulation of cell- cycle progression is unclear. In the present study, we have found for the first time that NFBD1 is phosphorylated by polo-like kinase 1 (PLK1) and has an important role in G2/M transition. Both NFBD1 and PLK1 are co-expressed in cellular nuclei throughout G2/M transition, and binding assays demonstrated direct interaction between NFBD1 and PLK1. Indeed, in vitro kinase reactions revealed that the PST domain of NFBD1 contains a potential amino acid sequence (845-DVTGEE-850) targeted by PLK1. Furthermore, enforced expression of GFP-PST but not GFP-PST(T847A) where threonine at 847 was substituted by alanine inhibited the phosphorylation levels of histone H3, suggesting a defect of M phase entry. Because PLK1 has been implicated in promoting the G2/M transition, we reasoned that overexpressed PST might serve as a pseudosubstrate for PLK1 and thus interfere with phosphorylation of endogenous PLK1 substrates. Interestingly, siRNA-mediated knockdown of NFBD1 resulted in early M phase entry and accelerated M phase progression, raising the possibility that NFBD1 is a PLK1 substrate for regulating the G2/M transition. Moreover, the constitutive active form of PLK1(T210D) overcame the ICRF-193-induced decatenation checkpoint and inhibited the interaction between NFBD1 and topoisomerase IIα, but kinase-deficient PLK1 did not. Based on these observations, we propose that PLK1-mediated phosphorylation of NFBD1 is involved in the regulation of G2/M transition by recovering a decatenation checkpoint.

Smc5/6-mediated regulation of replication progression contributes to chromosome assembly during mitosis in human cells

The Smc5/6 complex plays a critical role in processing DNA replication and is indispensable for sister chromatid assembly and faithful segregation in mitosis.

The structural maintenance of chromosomes (SMC) proteins constitute the core of critical complexes involved in structural organization of chromosomes. In yeast, the Smc5/6 complex is known to mediate repair of DNA breaks and replication of repetitive genomic regions, including ribosomal DNA loci and telomeres. In mammalian cells, which have diverse genome structure and scale from yeast, the Smc5/6 complex has also been implicated in DNA damage response, but its further function in unchallenged conditions remains elusive. In this study, we addressed the behavior and function of Smc5/6 during the cell cycle. Chromatin fractionation, immunofluorescence, and live-cell imaging analyses indicated that Smc5/6 associates with chromatin during interphase but largely dissociates from chromosomes when they condense in mitosis. Depletion of Smc5 and Smc6 resulted in aberrant mitotic chromosome phenotypes that were accompanied by the abnormal distribution of topoisomerase IIα (topo IIα) and condensins and by chromosome segregation errors. Importantly, interphase chromatin structure indicated by the premature chromosome condensation assay suggested that Smc5/6 is required for the on-time progression of DNA replication and subsequent binding of topo IIα on replicated chromatids. These results indicate an essential role of the Smc5/6 complex in processing DNA replication, which becomes indispensable for proper sister chromatid assembly in mitosis.