ABSTRACT
JRK is a DNA-binding protein of the pogo superfamily of transposons, which includes the well-known centromere binding protein B (CENP-B). Jrk null mice exhibit epilepsy, and growth and reproductive disorders, consistent with its relatively high expression in the brain and reproductive tissues. Human JRK DNA variants and gene expression levels are implicated in cancers and neuropsychiatric disorders. JRK protein modulates ß-catenin-TCF activity but little is known of its cellular functions. Based on its homology to CENP-B, we determined whether JRK binds centromeric or other satellite DNAs. We show that human JRK binds satellite III DNA, which is abundant at the chromosome 9q12 juxtacentromeric region and on Yq12, both sites of nuclear stress body assembly. Human JRK-GFP overexpressed in HeLa cells strongly localises to 9q12. Using an anti-JRK antiserum we show that endogenous JRK co-localises with a subset of centromeres in non-stressed cells, and with heat shock factor 1 following heat shock. Knockdown of JRK in HeLa cells proportionately reduces heat shock protein gene expression in heat-shocked cells. A role for JRK in regulating the heat shock response is consistent with the mouse Jrk null phenotype and suggests that human JRK may act as a modifier of diseases with a cellular stress component.
Subject(s)
DNA, Satellite , DNA-Binding Proteins , Heat-Shock Response , Animals , Humans , Mice , Centromere/metabolism , Centromere Protein B/metabolism , Centromere Protein B/genetics , DNA, Satellite/genetics , DNA, Satellite/metabolism , DNA-Binding Proteins/metabolism , DNA-Binding Proteins/genetics , HeLa Cells , Protein BindingABSTRACT
Centromeres are chromatin structures specialized in sister chromatid cohesion, kinetochore assembly, and microtubule attachment during chromosome segregation. The regional centromere of vertebrates consists of long regions of highly repetitive sequences occupied by the Histone H3 variant CENP-A, and which are flanked by pericentromeres. The three-dimensional organization of centromeric chromatin is paramount for its functionality and its ability to withstand spindle forces. Alongside CENP-A, key contributors to the folding of this structure include components of the Constitutive Centromere-Associated Network (CCAN), the protein CENP-B, and condensin and cohesin complexes. Despite its importance, the intricate architecture of the regional centromere of vertebrates remains largely unknown. Recent advancements in long-read sequencing, super-resolution and cryo-electron microscopy, and chromosome conformation capture techniques have significantly improved our understanding of this structure at various levels, from the linear arrangement of centromeric sequences and their epigenetic landscape to their higher-order compaction. In this review, we discuss the latest insights on centromere organization and place them in the context of recent findings describing a bipartite higher-order organization of the centromere.
Subject(s)
Centromere , Chromatin , Chromosomal Proteins, Non-Histone , Vertebrates , Centromere/metabolism , Centromere/ultrastructure , Animals , Chromatin/metabolism , Chromatin/genetics , Chromatin/ultrastructure , Chromatin/chemistry , Humans , Chromosomal Proteins, Non-Histone/metabolism , Chromosomal Proteins, Non-Histone/chemistry , Chromosomal Proteins, Non-Histone/genetics , Vertebrates/genetics , Centromere Protein A/metabolism , Centromere Protein A/genetics , Cohesins , Multiprotein Complexes/metabolism , Multiprotein Complexes/ultrastructure , Centromere Protein B/metabolism , Centromere Protein B/genetics , DNA-Binding Proteins/metabolism , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/genetics , Cell Cycle Proteins/metabolism , Cell Cycle Proteins/genetics , Cell Cycle Proteins/ultrastructure , Adenosine TriphosphatasesABSTRACT
OBJECTIVES: Antinuclear antibodies (ANA) of the IgE-type have been described in several connective tissue disorders (CTD) but not yet in systemic sclerosis (SSc). Aim of the study was, therefore, to establish an ELISA for the demonstration of IgE-autoantibodies to topoisomerase-I (topo-I) and the centromeric proteins A and B (CENP-A/B), to assess their prevalence and reactivity in SSc and to analyse their clinical relevance. METHODS: One hundred fifty-one patients with SSc and 88 with CREST-syndrome, 291 patients with other CTD, and 23 patients with fibromyalgia syndrome (FM) as a control collective were included into the study. Patients' sera were analysed by an in-house-ELISA for IgE autoantibodies against topo-I and CENP-A/B using recombinant antigens. Patients were assessed for median Rodnan skin score(mRSS), different organ and cutaneous manifestations. RESULTS: Of the patients with CREST syndrome, 67% had IgE-anti-CENP-A- and 77% IgE-anti-CENP-B-antibodies. IgE-anti-topo-I antibodies were found in 56% of patients with SSc. Prevalence and reactivity were significantly higher in CREST and SSc, respectively, than in other CTD or FM. IgE-reactivity strongly correlated with IgG-antibody reactivity. In CRESTsyndrome, IgE-anti-CENP-A (but not CENP-B)-antibodies were significantly higher and more prevalent in patients with skin ulcers, high mRSS, and more than four organ manifestations. They did not correlate with blood eosinophil counts. In contrast, for IgE-anti-topo-I antibodies no correlation with clinical manifestations was observed. CONCLUSIONS: IgE-autoantibodies against CENP-A/B and topo-I occur in SSc underlining the concept that SSc may be a T helper cell type 2 mediated disease. IgE-anti-CENP-A-antibodies correlated with disease activity, but this has to be confirmed in larger studies.
Subject(s)
Centromere Protein A , Centromere Protein B , DNA Topoisomerases, Type I , Enzyme-Linked Immunosorbent Assay , Immunoglobulin E , Scleroderma, Systemic , Humans , Scleroderma, Systemic/immunology , Scleroderma, Systemic/blood , Scleroderma, Systemic/diagnosis , Female , DNA Topoisomerases, Type I/immunology , Male , Middle Aged , Immunoglobulin E/blood , Immunoglobulin E/immunology , Adult , Centromere Protein A/immunology , Centromere Protein B/immunology , Aged , Antibodies, Antinuclear/blood , Antibodies, Antinuclear/immunology , Autoantibodies/blood , Biomarkers/blood , Antigens, Nuclear/immunology , Autoantigens/immunology , Clinical RelevanceABSTRACT
Hepatocellular carcinoma (HCC) is a significant global health concern as it ranks as the sixth most common malignant tumor and the third leading cause of cancer-related deaths. In this study, we analyzed the expression of centromere protein B (CENPB) mRNA in HCC using TCGA and GEO datasets. Immunohistochemistry (IHC) was performed to determine CENPB protein levels in 490 HCC patients. Our findings revealed higher expression of CENPB mRNA in HCC tissues across the three datasets. Additionally, as the pathological stage and histological grade advanced, CENPB expression increased. Patients with elevated levels of CENPB mRNA and protein demonstrated shorter overall survival (OS) and recurrence-free survival (OS). Notably, CENPB protein showed prognostic value in patients with stage I/II, AFP levels below 400 ng/ml, and tumor size less than 5 cm. Using multivariate regression analysis in 490 HCC patients, we developed nomograms to predict 1-year, 3-year, and 5-year OS and RFS. Knockdown of CENPB in Hep3B and MHCC97 cell lines resulted in significant inhibition of cell proliferation and invasion. Furthermore, bioinformatics analysis identified miR-29a as a potential negative regulator of CENPB expression, which was validated through a dual-luciferase reporter assay. In conclusion, our findings suggest that CENPB may serve as an oncogenic factor in HCC and is directly regulated by miR-29a, highlighting its potential as a promising therapeutic target.
Subject(s)
Carcinoma, Hepatocellular , Liver Neoplasms , MicroRNAs , Humans , Carcinoma, Hepatocellular/pathology , Liver Neoplasms/pathology , MicroRNAs/metabolism , Centromere Protein B/genetics , Centromere Protein B/metabolism , RNA, Messenger , Cell Proliferation/genetics , Gene Expression Regulation, Neoplastic , Cell Line, TumorABSTRACT
Telomerase is a ribonucleoprotein enzyme that plays a crucial role in maintaining the malignancy and is responsible for cellular immortality and tumorigenesis. On another hand, Centromere protein B (CENP-B) plays an important role in cell cycle regulation and helping in the high rate proliferation of cancer cells. Our study is designed to evaluate the effect of using combined antisense oligonucleotides (ASOs) targeting (hTR) and mRNA of CENP-B on liver cancer cells. Compared with a single treatment, combination treatment with Locked Nucleic Acid (LNA) ASO (hTR) and (CENP-B) (6.25 nM from each) exhibit the maximum synergistic cytotoxic effect. hTR and CENP-B mRNA was abrogated while hTERT expression was disappeared. Caspase-3, Bax, and Bcl-2 were not detected, indicating caspase-independent cell death. A significant reduction in [Tumor necrosis factor (TNF-α) and Transforming growth factor (TGF-ß)] coincides with elevation in Nitric oxide (NO) secretions was observed. Taken together; our data suggest that combination treatment with LNA ASO (hTR) and (CENP-B) could provide a promising strategy for cancer treatment by controlling many pathways concurrently. This might open a new prospective application of antisense in cancer therapy.
Subject(s)
Antineoplastic Agents , Carcinoma, Hepatocellular , Liver Neoplasms , Telomerase , Carcinoma, Hepatocellular/therapy , Cell Line, Tumor , Centromere Protein B , Humans , Liver Neoplasms/therapy , Oligonucleotides, Antisense/pharmacology , RNA , RNA, Messenger/genetics , RNA, Messenger/metabolism , Telomerase/genetics , Telomerase/metabolismSubject(s)
Autoantibodies , Scleroderma, Systemic , Autoantigens , Centromere Protein B , Humans , VirulenceABSTRACT
Human artificial chromosomes (HACs) can be formed de novo by introducing large (>30 kb) centromeric sequences consisting of highly repeated 171-bp alpha satellite (alphoid) DNA into HT1080 cells. However, only a subset of transformed cells successfully establishes HACs. CENP-A chromatin and heterochromatin assemble on the HACs and play crucial roles in chromosome segregation. The CENP-B protein, which binds a 17-bp motif (CENP-B box) in the alphoid DNA, functions in the formation of alternative CENP-A chromatin or heterochromatin states. A balance in the coordinated assembly of these chromatin states on the introduced alphoid DNA is important for HAC formation. To obtain information about the relationship between chromatin architecture and de novo HAC formation efficiency, we tested combinations of two 60-kb synthetic alphoid sequences containing either tetO or lacO plus a functional or mutated CENP-B box combined with a multiple fusion protein tethering system. The combination of mutated and wild-type CENP-B box alphoid repeats significantly enhanced HAC formation. Both CENP-A and HP1α were enriched in the wild-type alphoid DNA, whereas H3K27me3 was enriched on the mutant alphoid array. The presence or absence of CENP-B binding resulted in differences in the assembly of CENP-A chromatin on alphoid arrays and the formation of H3K9me3 or H3K27me3 heterochromatin.
Subject(s)
Centromere Protein B , Chromosomes, Artificial, Human , Centromere Protein A/genetics , Centromere Protein B/genetics , Chromatin , DNA , Heterochromatin , Histones/metabolism , HumansABSTRACT
Radiotherapy represents the most effective nonsurgical therapy, whereas acquired radioresistance remains a major challenge in glioma treatment. Deregulation of long noncoding RNAs (lncRNAs) is frequently involved in tumorigenesis. This study investigates the role of LINC01123 in radioresistance in glioma with molecules involved. LINC01123 was identified as the most upregulated gene in a glioma gene expression dataset GSE103227. LINC01123 was highly expressed in the radioresistant glioma tissues radioresistant glioma U251 (U251R) cells. Downregulation of LINC01123 reduced cell proliferation and colony formation abilities, as well as resistance to apoptosis of the U251R cells after 4 Gy X-ray irradiation. The micro(mi)RNA-151a gene (miR-151a) was a poorly expressed miRNA in glioma, and it was a target of LINC01123. The centromere protein B gene (CENPB) mRNA was a direct target of miR-151a and demonstrated a positive correlation with LINC01123 in glioma tissues and cells. Further inhibition of miR-151a or overexpression of CENPB restored radioresistance of glioma cells. In addition, silencing of LINC01123 suppressed growth of xenograft tumors formed by U251R cells in nude mice. To conclude, the present study demonstrates that LINC01123 serves as a sponge for miR-151a and upregulates CENPB expression to increase the radioresistance of glioma cells in vitro and in vivo.
Subject(s)
Centromere Protein B/genetics , Glioma , MicroRNAs , RNA, Long Noncoding/genetics , Animals , Apoptosis , Cell Line, Tumor , Cell Proliferation , Gene Expression Regulation, Neoplastic , Glioma/genetics , Glioma/radiotherapy , Humans , Mice , Mice, Nude , MicroRNAs/genetics , Neoplasm TransplantationABSTRACT
The centromere is a chromosomal locus that is essential for the accurate segregation of chromosomes during cell division. Transcription of noncoding RNA (ncRNA) at the centromere plays a crucial role in centromere function. The zinc-finger transcriptional regulator ZFAT binds to a specific 8-bp DNA sequence at the centromere, named the ZFAT box, to control ncRNA transcription. However, the precise molecular mechanisms by which ZFAT localizes to the centromere remain elusive. Here we show that the centromeric protein CENP-B is required for the centromeric localization of ZFAT to regulate ncRNA transcription. The ectopic expression of CENP-B induces the accumulation of both endogenous and ectopically expressed ZFAT protein at the centromere in human cells, suggesting that the centromeric localization of ZFAT requires the presence of CENP-B. Coimmunoprecipitation analysis reveals that ZFAT interacts with the acidic domain of CENP-B, and depletion of endogenous CENP-B reduces the centromeric levels of ZFAT protein, further supporting that CENP-B is required for the centromeric localization of ZFAT. In addition, knockdown of CENP-B significantly decreased the expression levels of ncRNA at the centromere where ZFAT regulates the transcription, suggesting that CENP-B is involved in the ZFAT-regulated centromeric ncRNA transcription. Thus, we concluded that CENP-B contributes to the establishment of the centromeric localization of ZFAT to regulate ncRNA transcription.
Subject(s)
Centromere Protein B/metabolism , Centromere/metabolism , RNA, Untranslated/biosynthesis , Transcription Factors/metabolism , Transcription, Genetic , Animals , Centromere/genetics , Centromere Protein B/genetics , HEK293 Cells , HeLa Cells , Humans , Mice , NIH 3T3 Cells , RNA, Untranslated/genetics , Transcription Factors/geneticsABSTRACT
BACKGROUND: Anticentromere antibody (ACA) is a member of the antinuclear antibody spectrum (ANAs) which has been speculated to be associated with subfertility. Thus, the present study aimed to investigate the induction of ACA production and its potential interference with early-stage embryos. METHODS: Recombinant centromere protein-A (CENP-A) or centromere protein-B (CENP-B) and complete Freund's adjuvant (CFA) were used to immunize mice. Serum ACA level was then evaluated by using an indirect immunofluorescence test. Immunofluorescence assay was performed to detect IgG in follicles in ovarian tissues and early-stage embryos. RESULTS: Following treatment, serum positive ACA was observed in mice treated with CENP and CFA. Furthermore, IgG were detected in follicular fluid and early-stage embryos from mice treated with CENP and CFA. CONCLUSIONS: This study preliminarily indicated that ACA induced by CENP and CFA may penetrate into the living embryos of early-stage in mice.
Subject(s)
Antibodies, Antinuclear/immunology , Blastocyst/immunology , Follicular Fluid/immunology , Immunoglobulin G/immunology , Ovarian Follicle/immunology , Animals , Centromere Protein A/immunology , Centromere Protein B/immunology , Chorionic Gonadotropin , Embryo, Mammalian/immunology , Female , Freund's Adjuvant , Gonadotropins, Equine , In Vitro Oocyte Maturation Techniques , Mice , Ovulation Induction , VaccinationABSTRACT
Selfish centromere DNA sequences bias their transmission to the egg in female meiosis. Evolutionary theory suggests that centromere proteins evolve to suppress costs of this "centromere drive." In hybrid mouse models with genetically different maternal and paternal centromeres, selfish centromere DNA exploits a kinetochore pathway to recruit microtubule-destabilizing proteins that act as drive effectors. We show that such functional differences are suppressed by a parallel pathway for effector recruitment by heterochromatin, which is similar between centromeres in this system. Disrupting the kinetochore pathway with a divergent allele of CENP-C reduces functional differences between centromeres, whereas disrupting heterochromatin by CENP-B deletion amplifies the differences. Molecular evolution analyses using Murinae genomes identify adaptive evolution in proteins in both pathways. We propose that centromere proteins have recurrently evolved to minimize the kinetochore pathway, which is exploited by selfish DNA, relative to the heterochromatin pathway that equalizes centromeres, while maintaining essential functions.
Subject(s)
Centromere Protein B/metabolism , Centromere/metabolism , Chromosomal Proteins, Non-Histone/metabolism , Alleles , Amino Acid Sequence , Animals , Biological Evolution , CRISPR-Cas Systems/genetics , Centromere Protein A/metabolism , Chromosomal Proteins, Non-Histone/chemistry , Chromosomes, Mammalian/metabolism , Female , Heterochromatin/metabolism , Kinetochores/metabolism , Male , Mice, Inbred C57BL , Models, Biological , Oocytes/metabolism , Protein DomainsABSTRACT
Human centromeres are mainly composed of alpha satellite DNA hierarchically organized as higher-order repeats (HORs). Alpha satellite dynamics is shown by sequence homogenization in centromeric arrays and by its transfer to other centromeric locations, for example, during the maturation of new centromeres. We identified during prenatal aneuploidy diagnosis by fluorescent in situ hybridization a de novo insertion of alpha satellite DNA from the centromere of chromosome 18 (D18Z1) into cytoband 15q26. Although bound by CENP-B, this locus did not acquire centromeric functionality as demonstrated by the lack of constriction and the absence of CENP-A binding. The insertion was associated with a 2.8-kbp deletion and likely occurred in the paternal germline. The site was enriched in long terminal repeats and located â¼10 Mbp from the location where a centromere was ancestrally seeded and became inactive in the common ancestor of humans and apes 20-25 million years ago. Long-read mapping to the T2T-CHM13 human genome assembly revealed that the insertion derives from a specific region of chromosome 18 centromeric 12-mer HOR array in which the monomer size follows a regular pattern. The rearrangement did not directly disrupt any gene or predicted regulatory element and did not alter the methylation status of the surrounding region, consistent with the absence of phenotypic consequences in the carrier. This case demonstrates a likely rare but new class of structural variation that we name "alpha satellite insertion." It also expands our knowledge on alphoid DNA dynamics and conveys the possibility that alphoid arrays can relocate near vestigial centromeric sites.
Subject(s)
Centromere , Chromosomal Proteins, Non-Histone , Centromere/genetics , Centromere/metabolism , Centromere Protein B/genetics , Centromere Protein B/metabolism , Chromosomal Proteins, Non-Histone/genetics , DNA, Satellite/genetics , Humans , In Situ Hybridization, FluorescenceABSTRACT
Systemic sclerosis (SSc) is associated, in nearly all patients, with autoantibodies (Ab). Accordingly, and in order to identify major (anti-CEN A/B and anti-Topo I) but also minor Abs, the usefulness of combining indirect immunofluorescence (IIF) on HEp-2 cells with an 11 multi-antigenic SSc immunodot was explored. 1689 samples tested at the request of clinicians, were evaluated retrospectively. The positivity rate was 28.8% and the diagnosis of SSc was supported for 232 samples. Two groups of Abs were considered: group 1, Abs (anti-CENP A/B, anti-Topo I) present at elevated levels in SSc patients; group 2, Abs for which the Ab specificity (odds ratio and/or positive predictive value) was improved by using IIF on HEp-2 cells (RNA-Polymerase III, fibrillarin, Th/T0, PM-Scl). Altogether, this study highlights the utility of combining IIF on HEp-2 cells with the SSc immunodot as the first line of an SSc Abs detection/SSc diagnostic strategy.
Subject(s)
Autoantibodies/blood , Fluorescent Antibody Technique, Indirect/methods , Immunoblotting/methods , Scleroderma, Systemic/diagnosis , Scleroderma, Systemic/immunology , Adult , Aged , Autoantigens/immunology , Cell Line , Centromere Protein A/immunology , Centromere Protein B/immunology , DNA Topoisomerases, Type I/immunology , Female , Humans , Male , Middle Aged , Retrospective StudiesABSTRACT
Centromeric transcription has been shown to play an important role in centromere functions. However, lack of approaches to specifically manipulate centromeric transcription calls into question that the proposed functions are a direct consequence of centromeric transcription. By monitoring nascent RNAs, we found that several transcriptional inhibitors exhibited distinct, even opposing, efficacies on the suppression of ongoing gene and centromeric transcription in human cells, whereas under the same conditions, total centromeric RNAs were changed to a lesser extent. The inhibitor suppressing ongoing centromeric transcription weakened centromeric cohesion, whereas the inhibitor increasing ongoing centromeric transcription strengthened centromeric cohesion. Furthermore, expression of CENP-B DNA-binding domain or CENP-B knockdown moderately increased centromeric transcription without altering gene transcription; as a result, centromeric cohesion was accordingly strengthened. Targeting of the Kox1-KRAB domain with CENP-B DB to centromeres specifically decreased centromeric transcription and weakened centromeric cohesion. Thus, based on these findings, we propose that a major function of centromeric transcription is to maintain centromeric cohesion in human cells.
Subject(s)
Centromere Protein B/genetics , Centromere/genetics , Kruppel-Like Transcription Factors/genetics , Repressor Proteins/genetics , Transcription, Genetic , Chromatin/genetics , Chromosomal Proteins, Non-Histone/genetics , DNA-Binding Proteins/genetics , Histones/genetics , Humans , Mitosis/genetics , Protein Binding/geneticsABSTRACT
The essential transcription factor PoxCxrA is required for cellulase and xylanase gene expression in the filamentous fungus Penicillium oxalicum that is potentially applied in biotechnological industry as a result of the existence of the integrated cellulolytic and xylolytic system. However, the regulatory mechanism of cellulase and xylanase gene expression specifically associated with PoxCxrA regulation in fungi is poorly understood. In this study, the novel regulator PoxCbh (POX06865), containing a centromere protein B-type helix-turn-helix domain, was identified through screening for the PoxCxrA regulon under Avicel induction and genetic analysis. The mutant ∆PoxCbh showed significant reduction in cellulase and xylanase production, ranging from 28.4% to 59.8%. Furthermore, PoxCbh was found to directly regulate the expression of important cellulase and xylanase genes, as well as the known regulatory genes PoxNsdD and POX02484, and its expression was directly controlled by PoxCxrA. The PoxCbh-binding DNA sequence in the promoter region of the cellobiohydrolase 1 gene cbh1 was identified. These results expand our understanding of the diverse roles of centromere protein B-like protein, the regulatory network of cellulase and xylanase gene expression, and regulatory mechanisms in fungi.
Subject(s)
Centromere Protein B/genetics , Chromosomal Proteins, Non-Histone/biosynthesis , Gene Expression Regulation, Fungal/genetics , Helix-Turn-Helix Motifs/genetics , Penicillium/genetics , Penicillium/metabolism , Cellulase/biosynthesis , Cellulase/genetics , Cellulose 1,4-beta-Cellobiosidase/genetics , Centromere Protein B/biosynthesis , Chromosomal Proteins, Non-Histone/genetics , Endo-1,4-beta Xylanases/biosynthesis , Endo-1,4-beta Xylanases/genetics , Transcription Factors/geneticsABSTRACT
1-Methylpyrene (1-MP) is a common environmental pollutant and animal carcinogen. After sequential activation by cytochromes P450 and sulfotransferases, it induced gene mutations and micronuclei in mammalian cells. The type of micronuclei formed, entire chromosomes or fragments, was not analysed. In this study, 1-MP and its primary metabolite, 1-hydroxymethylpyrene (1-HMP), were investigated for the induction of centromere-positive and -negative micronuclei in the human hepatoma cell line HepG2 and its derivative C3A, expressing relevant enzymes at higher levels. Under a short-exposure (9 h)/long-recovery regime (2 cell cycles in total), 1-MP and 1-HMP provided negative test results in HepG2 cells. However, they induced micronuclei in C3A cells, the effect being blocked by 1-aminobenzotriazole (inhibitor of cytochromes P450s) and reduced by pentachlorophenol (inhibitor of sulfotransferases). Immunofluorescence staining of centromere protein B in the micronuclei revealed purely clastogenic effects under this regime. Unexpectedly, 1-MP and 1-HMP at concentrations 1/5-1/4 of that required for micronuclei formation led to mitotic arrest and spindle aberrations, as detected by immunofluorescence staining of ß- and γ-tubulin. Following extended exposure (72 h, 2 cell cycles, no recovery), damage to the spindle apparatus and centrosomes was detected at even lower concentrations, with concurrent formation of micronuclei. At low concentrations (1-8 µM 1-MP, 0.25-0.5 µM 1-HMP), the micronuclei induced were unexceptionally centromere-positive. Thus, the chromosome-damaging mechanism of 1-MP was regime and concentration dependent: potently aneugenic under persistent exposure, while clastogenic at higher concentrations following a short-exposure/long-recovery regime. This is a convincing evidence for the existence of metabolic activation-dependent aneugens.
Subject(s)
Micronuclei, Chromosome-Defective/drug effects , Mitosis/drug effects , Pyrenes/toxicity , Activation, Metabolic/drug effects , Aneugens/metabolism , Aneugens/toxicity , Cell Line, Tumor , Centromere Protein B/metabolism , Centrosome/drug effects , Hep G2 Cells , Humans , Micronucleus Tests , Microscopy, Fluorescence , Mutagens , Pyrenes/metabolism , Spindle Apparatus/drug effectsABSTRACT
The centromere is an essential chromatin domain required for kinetochore recruitment and chromosome segregation in eukaryotes. To perform this role, centro-chromatin adopts a unique structure that provides access to kinetochore proteins and maintains stability under tension during mitosis. This is achieved by the presence of nucleosomes containing the H3 variant CENP-A, which also acts as the epigenetic mark defining the centromere. In this review, we discuss the role of CENP-A on the structure and dynamics of centromeric chromatin. We further discuss the impact of the CENP-A binding proteins CENP-C, CENP-N, and CENP-B on modulating centro-chromatin structure. Based on these findings we provide an overview of the higher order structure of the centromere.
Subject(s)
Centromere Protein A/chemistry , Centromere Protein B/chemistry , Centromere/ultrastructure , Chromatin/ultrastructure , Chromosomal Proteins, Non-Histone/chemistry , Adenosine Triphosphatases/chemistry , Adenosine Triphosphatases/genetics , Adenosine Triphosphatases/metabolism , Cell Cycle Proteins/chemistry , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Centromere/chemistry , Centromere/metabolism , Centromere Protein A/genetics , Centromere Protein A/metabolism , Centromere Protein B/genetics , Centromere Protein B/metabolism , Chromatin/chemistry , Chromatin/metabolism , Chromosomal Proteins, Non-Histone/genetics , Chromosomal Proteins, Non-Histone/metabolism , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Epigenesis, Genetic , Humans , Mitosis , Models, Molecular , Multiprotein Complexes/chemistry , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Nucleic Acid Conformation , Protein Binding , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolism , CohesinsABSTRACT
Human artificial chromosomes (HACs) are important tools for epigenetic engineering, for measuring chromosome instability (CIN), and for possible gene therapy. However, their use in the latter is potentially limited because the input HAC-seeding DNA can undergo an unpredictable series of rearrangements during HAC formation. As a result, after transfection and HAC formation, each cell clone contains a HAC with a unique structure that cannot be precisely predicted from the structure of the HAC-seeding DNA. Although it has been reported that these rearrangements can happen, the timing and mechanism of their formation has yet to be described. Here we synthesized a HAC-seeding DNA with two distinct structural domains and introduced it into HT1080 cells. We characterized a number of HAC-containing clones and subclones to track DNA rearrangements during HAC establishment. We demonstrated that rearrangements can occur early during HAC formation. Subsequently, the established HAC genomic organization is stably maintained across many cell generations. Thus, early stages in HAC formation appear to at least occasionally involve a process of DNA shredding and shuffling that resembles chromothripsis, an important hallmark of many cancer types. Understanding these events during HAC formation has critical implications for future efforts aimed at synthesizing and exploiting synthetic human chromosomes.
Subject(s)
Chromosomes, Artificial, Human/metabolism , Gene Rearrangement/physiology , Cell Line, Tumor , Centromere/metabolism , Centromere Protein B/genetics , Chromosomal Instability , Epigenesis, Genetic , Genetic Vectors/genetics , Genetic Vectors/metabolism , HumansABSTRACT
1-Methylpyrene (1-MP) is a ubiquitous environmental pollutant and rodent carcinogen. Its mutagenic activity depends on sequential activation by various CYP and sulfotransferase (SULT) enzymes. Previously we have observed induction of micronuclei and mitotic arrest by 1-MP in a Chinese hamster (V79)-derived cell line expressing both human CYP1A2 and SULT1A1 (V79-hCYP1A2-hSULT1A1), however, the mode of chromosome damage and the involvement of mitotic tubulin structures have not been clarified. In this study, we used immunofluorescent staining of centromere protein B (CENP-B) with the formed micronuclei, and that of ß- and γ-tubulin reflecting the structures of mitotic spindle and centrioles, respectively, in V79-hCYP1A2-hSULT1A1 cells. The results indicated that 1-MP induced micronuclei in V79-hCYP1A2-hSULT1A1 cells from 0.125 to 2 µM under a 24 h/0 h (exposure/recovery) regime, while in the parental V79-Mz cells micronuclei were induced by 1-MP only at concentrations ≥ 8 µM; in both cases, the micronuclei induced by 1-MP were predominantly CENP-B positive. Following 54 h of exposure, 1-MP induced mitotic spindle non-congression and centrosome amplification (multipolar mitosis) in V79-hCYP1A2-hSULT1A1 cells, and anaphase/telophase retardation, at concentrations ≥ 0.125 µM with concentration-dependence; while in V79-Mz cells it was inactive up to 8 µM. This study suggests that in mammalian cells proficient in activating enzymes 1-MP may induce chromosome loss and mitotic disturbance, probably by interfering with the mitotic spindle and centrioles.
Subject(s)
Arylsulfotransferase/metabolism , Chromosomes, Mammalian/metabolism , Cytochrome P-450 CYP1A2/metabolism , Mitosis/drug effects , Pyrenes/pharmacology , Animals , Cell Line , Cell Shape/drug effects , Cell Survival/drug effects , Centromere Protein B/metabolism , Cricetinae , Humans , Micronucleus, Germline/drug effects , Micronucleus, Germline/metabolism , Mitotic Index , Spindle Apparatus/drug effects , Spindle Apparatus/metabolismABSTRACT
Centromeres are built on repetitive DNA sequences (CenDNA) and a specific chromatin enriched with the histone H3 variant CENP-A, the epigenetic mark that identifies centromere position. Here, we interrogate the importance of CenDNA in centromere specification by developing a system to rapidly remove and reactivate CENP-A (CENP-AOFF/ON ). Using this system, we define the temporal cascade of events necessary to maintain centromere position. We unveil that CENP-B bound to CenDNA provides memory for maintenance on human centromeres by promoting de novo CENP-A deposition. Indeed, lack of CENP-B favors neocentromere formation under selective pressure. Occasionally, CENP-B triggers centromere re-activation initiated by CENP-C, but not CENP-A, recruitment at both ectopic and native centromeres. This is then sufficient to initiate the CENP-A-based epigenetic loop. Finally, we identify a population of CENP-A-negative, CENP-B/C-positive resting CD4+ T cells capable to re-express and reassembles CENP-A upon cell cycle entry, demonstrating the physiological importance of the genetic memory.