Chromosome Condensation Research Articles

SNORA73B promotes endometrial cancer progression through targeting MIB1 and regulating host gene RCC1 alternative splicing.

Endometrial cancer (EC) is a common gynaecological malignant tumour with unclear pathogenesis. Small nucleolar RNA (snoRNA) is involved in many biological processes, including those of cancers. Using the Cancer Genome Atlas (TCGA) database, the expression pattern of a snoRNA, SNORA73B, was analysed. The biological functions of SNORA73B were assessed by in vitro proliferation, apoptosis, migration, and invasion assays and in vivo by the xenograft model. RNA sequencing (RNA-seq) and RNA immunoprecipitation assays were performed to determine the relationship between SNORA73B and its target genes. High-performance liquid chromatography (HPLC) was performed to detect the pseudouridine content of the mindbomb E3 ubiquitin protein ligase 1 gene (MIB1). The stability of MIB1 mRNA was evaluated using a transcription inhibitor, actinomycin D. By performing co-immunoprecipitation assays, the change in the ubiquitin levels of the Jagged canonical Notch ligand 1 (Jag 1), caused by SNORA73B and MIB1, was identified. RNA-seq and qRT-PCR were performed to detect the alternative splicing of the regulator of the chromosome condensation 1 gene (RCC1). The TCGA database analysis showed that SNORA73B was highly expressed in EC. SNORA73B promoted cell proliferation, migration, and invasion and inhibited apoptosis. SNORA73B modified the pseudouridine content in MIB1 and increased the stability of MIB1 mRNA and protein; thus, it affected Jag 1 ubiquitination and further activated the Notch pathway. SNORA73B also affected the alternative splicing of RCC1, increasing the number of transcripts, RCC1-T2 and RCC1-T3, which promoted cell proliferation, migration, and invasion. SNORA73B can be a potential target for EC.

Centripetal nuclear shape fluctuations associate with chromatin condensation in early prophase

The nucleus plays a central role in several key cellular processes, including chromosome organisation, DNA replication and gene transcription. Recent work suggests an association between nuclear mechanics and cell-cycle progression, but many aspects of this connection remain unexplored. Here, by monitoring nuclear shape fluctuations at different cell cycle stages, we uncover increasing inward fluctuations in late G2 and in early prophase, which are initially transient, but develop into instabilities when approaching the nuclear-envelope breakdown. We demonstrate that such deformations correlate with chromatin condensation by perturbing both the chromatin and the cytoskeletal structures. We propose that the contrasting forces between an extensile stress and centripetal pulling from chromatin condensation could mechanically link chromosome condensation with nuclear-envelope breakdown, two main nuclear processes occurring during mitosis.

Spatial organization and dynamics of chromosomes and microtubules during barley mitosis.

Mitosis and cytokinesis are fundamental processes through which somatic cells increase their numbers and allow plant growth and development. Here, we analyzed the organization and dynamics of mitotic chromosomes, nucleoli, and microtubules in living cells of barley root primary meristems using a series of newly developed stable fluorescent protein translational fusion lines and time-lapse confocal microscopy. The median duration of mitosis from prophase until the end of telophase was 65.2 and 78.2 min until the end of cytokinesis. We showed that barley chromosomes frequently start condensation before mitotic pre-prophase as defined by the organization of microtubules and maintain it even after entering into the new interphase. Furthermore, we found that the process of chromosome condensation does not finish at metaphase, but gradually continues until the end of mitosis. In summary, our study features resources for in vivo analysis of barley nuclei and chromosomes and their dynamics during mitotic cell cycle.

Early chromosome condensation by XIST builds A-repeat RNA density that facilitates gene silencing

XIST RNA triggers chromosome-wide gene silencing and condenses an active chromosome into a Barr body. Here, we use inducible human XIST to examine early steps in the process, showing that XIST modifies cytoarchitecture before widespread gene silencing. In just 2-4 h, barely visible transcripts populate the large "sparse zone" surrounding the smaller "dense zone"; importantly, density zones exhibit different chromatin impacts. Sparse transcripts immediately trigger immunofluorescence for H2AK119ub and CIZ1, a matrix protein. H3K27me3 appears hours later in the dense zone, which enlarges with chromosome condensation. Genes examined are silenced after compaction of the RNA/DNA territory. Insights into this come from the findings that the A-repeat alone can silence genes and rapidly, but only where dense RNA supports sustained histone deacetylation. We propose that sparse XIST RNA quickly impacts architectural elements to condense the largely non-coding chromosome, coalescing RNA density that facilitates an unstable, A-repeat-dependent step required for gene silencing.

P-237 In vitro time to maturation of Metaphase I oocytes: a time-lapse study correlating blastocyst formation and ploidy status

Abstract Study question What is the impact of metaphase I (MI) time to mature period (TTM) regarding blastocyst development and ploidy status? Summary answer A short period of TTM (0.1 to 1.0) is related to an increase number of blastocyst formation when compared to longer TTM (1.1 to 3.0). What is known already To achieve meiotic competence, coordinated nuclear and cytoplasmic changes must occur in the oocyte to support fertilization and DNA replication and to ensure correct ploidy of the zygote and embryonic genome activation. Concomitant with chromosome condensation and migration, oocyte maturation goes by cytoplasm reorganization throughout the transitions of MI, polar body extrusion and MII. Despite the optimization of COH protocols, nearly 20% of the retrieved oocytes remain immature at the GV or MI stages. In vitro maturation of MI could increase the number of available embryos; however, longer culture time may affect oocyte quality, resulting in abnormal fertilization and cleavage. Study design, size, duration Prospective cohort study from 244 patients (n = 277 cycles) that had at least 1 MI oocyte after oocyte retrieval (OPU) following controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF) treatment according to medical referral in an single private ART center from January/2019 to November/2022. All MI oocytes were placed in a time-lapse incubator (TL, EmbryoScope, Vitrolife, Sweden) to check the exact time of first polar body extrusion (TTM to MII) before intracytoplasmic sperm injection (ICSI). Participants/materials, setting, methods Three hours after OPU, oocytes were denuded and assessed for maturation. Six-hundred and seven MI oocytes were followed in TL and those that reached the MII stage in a maximum of 6 hours post-OPU, were injected by ICSI (at 6h post-OPU) and stratified according to the TTM (0.1-1.0 hours and 1.1-3.0 hours). Fertilization rate, blastocyst formation, and ploidy were assessed. Kruskal-Wallis, chi-squared and Fisher tests were applied for statistical analysis. p < 0,05 was considered significant. Main results and the role of chance Patient mean age (n = 244) was 38,50 ± 3,40 years. From those, 25 patients (10.3%) had 2 cycles and 4 patients (1.6%) had 3 cycles with at least 1 MI oocyte. Age, anti-Müllerian hormone (AMH), #OPU, #MII, %MII (MII/OPU), #MI and MI% (MI/OPU) mean were not statistically different in patients with 1, 2 or 3 cycles in our cohort. One hundred forty-nine patients (61%) in 165 cycles (59.6%) had at least 1 oocyte that reached MII stage. In total, 248 oocytes were injected after 0.1-1.0h (group 1, n = 104, 41.9%) and 1.1-3.0h (group 2, n = 144 oocytes, 58.1%) of in vitro maturation. Age (38,99 ± 3,01 vs 38,85 ± 3,31), AMH (1,27 ± 1,29 vs 1,63 ± 1,87), #OPU (8,98 ± 4,32 vs 8,90 ± 4,34), #MII (4,41 ± 2,74 vs 4,44 ± 2,178), %MII (47.6% ± 18.8% vs 48.4% ± 17.1%) and %MI that followed to ICSI (59.2% ± 28.5% vs 54.8% ± 29.2%) were not different between groups 1 and 2 respectively. The mean number of MI that followed to ICSI were higher in group 1 (1,28 ± 0,48 vs 1,10 ± 0,32, p = 0.0008). Normal fertilization (2PN) and embryo cleavage were similar between groups (54.8% vs 45.1%, p = 0.157, 96.6% vs 93.3%, p = 0.467, respectively). However, blastocyst formation rate (#blastocyst/#fertilized) was higher in group 1 (n = 33, 55.9% vs n = 26, 34.7%, p = 0.015). Euploidy rates were similar between groups (9/28, 32% vs 4/24, 16%, p = 0.336). Limitations, reasons for caution Besides the retrospective nature of this study, male factor and infertility reason were not considered in this analysis. Due to the low number of blastocyst formation and consequentially ploidy assessment and number of embryo transfer, the results regarding euploidy rate may be underestimated and pregnancy rates were not included. Wider implications of the findings Oocytes that reached maturity up to 1 hour after denudation showed higher blastocyst formation rate, thus increasing embryo availability to transfer. In vitro-matured oocytes exhibit increased spindle and chromosomal abnormalities compared with oocytes matured in vivo, which may explain the lower rates of euploid embryos, especially in group 2. Trial registration number Not applicable.

Preliminary Study on the Expression of CLLD7 and CHC1L Proteins in Oral Squamous Cell Carcinoma.

This study aimed to preliminarily evaluate the expression of two putative tumor suppressor proteins, including chronic lymphocytic leukemia deletion gene 7 (CLLD7) and chromosome condensation 1-like (CHC1L) proteins in oral squamous cell carcinoma (OSCC). Expression of CLLD7 and CHC1L proteins was analyzed in 19 OSCC and 12 normal oral mucosa (NOM) using immunohistochemistry. The percentage of positive cells and intensity of staining were semiquantitatively assessed and expressed with an immunoreactive score. The number of positive cells at various subcellular localizations was evaluated and presented in percentages. The immunoreactivity scores and percentages of positive cells at various localizations were compared between the normal and OSCC groups with statistical significance at p-value less than 0.05. According to immunohistochemical analysis, the immunoreactivity scores for both CLLD7 and CHC1L were higher in NOM than those of OSCC. Analysis of CLLD7 localization revealed predominant nuclear staining at basal and parabasal areas in NOM, whereas more cytoplasmic staining was observed in OSCC. For CHC1L, nuclear staining was prominent in NOM. In contrast, significantly increased plasma membrane staining was detected in OSCC. The expression of CLLD7 and CHC1L proteins was reduced in OSCC. Alterations in the subcellular localization of these two proteins in OSCC were also demonstrated. These preliminary results suggest that CLLD7 and CHC1L are aberrantly expressed in OSCC. The precise mechanisms of these putative tumor suppressor proteins in OSCC require future studies.

Phosphatase-dependent function of PTEN in maintaining mitotic chromatin condensation

The process for genetic transmission takes place in a chromatin environment constituted of histones and non-histone architectural proteins. PTEN, a potent tumor suppressor defective in a large number of human cancers, has been found to interact with various chromatin components, guarding the genome against chromosome instability. Studies have shown that PTEN-deficient cells exhibit a globally defective chromatin environment. However, a comprehensive understanding of how the dynamic process of mitotic chromosome condensation is impacted by the PTEN-deficient epigenetic milieu is needed. Thus, the purpose of this study was to identify aberrations of dynamic mitotic chromatin compression resulting from PTEN dysfunction and to evaluate the importance of PTEN phosphatase activity in maintaining heterochromatin stability. An intrinsic metaphase structure assay was utilized to monitor the structural integrity of chromosomes in murine MC38 colon cancer cells. Following successive cycles of condensation and decondensation, MC38 cells with and without Pten were subjected to analysis of chromosome morphology. Pten-/cells exhibited fewer heterochromatic centers as compared to Pten+/+ cells. Ectopic expression of wild-type Pten (WT) rescued the aberrant heterochromatic morphology in Pten-null cells. In contrast, a lipid phosphatase deficient Pten mutant G129E (GE) failed to correct the Pten-deficient chromatin aberrations. These observations reveal that PTEN plays an essential role in maintaining mitotic chromosome stability and suggest that epigenetic approaches may be implemented to correct mitotic chromatin deregulation in tumors carrying PTEN mutations.

Multi-omic characterization of RCC1 expression and its association with molecular alterations, immune phenotypes, and cancer outcomes.

3128 Background: Regulator of Chromosome Condensation 1 (RCC1) is the only identified guanine nucleotide exchange factor for the Ras-related nuclear protein Ran and it functions in nuclear transport, cell cycle and DNA damage response. Overexpressed in several cancer types, RCC1 is associated with poor outcomes. We aim to investigate the role of aberrant RCC1 co-alterations and association with immune phenotypes and cancer outcomes. Methods: DNA (592-gene or whole exome)/RNA (whole transcriptome) sequencing was performed at Caris Life Sciences (Phoenix, AZ). Samples were stratified by RCC1 expression quartile thresholds (Q1:low, Q4:high) for small cell lung (SCLC, n=876), non-small cell lung (NSCLC, n=21603), gastric (GC, n=1908), pancreatic (PC, n=5071) and colorectal (CRC, n=14892) cancers. PD-L1+ expression was tested by IHC (22c3: ³1%; SP142: ³2+, 5%). TMB-High was defined as ³ 10 mutations/MB. Overall survival (OS) was calculated using Kaplan-Meier estimate. Statistical significance was determined using chi-square and Wilcoxon rank sum test and adjusted for multiple comparisons (*P<0.05). Results: Median RCC1 expression was highest in SCLC (14.3 transcript per million [TPM]), followed by GC (9.9), NSCLC (9.9), CRC (9.8), and PC (6.9). TMB-high rates increased progressively with RCC1 expression in NSCLC (Q1-Q4 range: 31-41%*), GC (7-22%*) and CRC (3-13%*), consistent with dMMR/MSI-high rates in GC (5-18%*) and CRC (3-13%*). Similar trends were observed for PDL1+ rates in PC (Q1-Q4 range: 13-20%*), CRC (2-5%*) and NSCLC (55-58%*). In NSCLC, TP53 (Q1-Q4 range: 57-77%*), RB1 (7-13%*), and EGFR (10-15%*) mutations were seen more with higher RCC1 expression, while STK11 (15-10%*) and KRAS (33-21%*) mutations were seen less. In PC, TP53 mutations (Q1-Q4 range: 70-85%*) and MYC amplifications (1-4%*) were seen more with RCC1 expression, whereas ATM mutations were seen less (6-3%). In CRC, TP53 (Q1-Q4 range: 70-81%*) and APC (72-81%*) mutations were seen more with RCC1 expression, while GNAS mutations were seen less (4-2%*). In both SCLC and NSCLC, high RCC1 expression was associated with increased dendritic cell (5-6%* and .8-1.3%*, respectively) and NK cell fractions (5-6%* and 2.5-3.2%*) and decreased Treg fractions (1.8-1.3%* and 3.0-2.6%*). In pMMR/MSS CRC, high RCC1 expression was associated with increased dendritic cell (.6-.9%*), NK cell (3-4%*), neutrophil (6-8%*) and CD4 T cell fractions (1.1-1.2%*) and decreased CD8 T cell (.5-.4%*) and Treg fractions (1.9-1.7%*). High RCC1 expression was associated with worse OS in NSCLC (HR 1.3*), PC (HR 1.5*) and CRC (HR 1.3*), with a similar but not significant effect in SCLC (HR 1.2) and GC (HR 1.2). Conclusions: RCC1 expression is a negative prognostic marker in NSCLC, PC, and CRC. Further studies to investigate this at the molecular level may be a potential opportunity for novel targeted drug development.

Granulosa cell mevalonate pathway abnormalities contribute to oocyte meiotic defects and aneuploidy.

With aging, abnormalities during oocyte meiosis become more prevalent. However, the mechanisms of aging-related oocyte aneuploidy are not fully understood. Here we performed Hi-C and SMART-seq of oocytes from young and old mice and reveal decreases in chromosome condensation and disrupted meiosis-associated gene expression in metaphase I oocytes from aged mice. Further transcriptomic analysis showed that meiotic maturation in young oocytes was correlated with robust increases in mevalonate (MVA) pathway gene expression in oocyte-surrounding granulosa cells (GCs), which was largely downregulated in aged GCs. Inhibition of MVA metabolism in GCs by statins resulted in marked meiotic defects and aneuploidy in young cumulus-oocyte complexes. Correspondingly, supplementation with the MVA isoprenoid geranylgeraniol ameliorated oocyte meiotic defects and aneuploidy in aged mice. Mechanically, we showed that geranylgeraniol activated LHR/EGF signaling in aged GCs and enhanced the meiosis-associated gene expression in oocytes. Collectively, we demonstrate that the MVA pathway in GCs is a critical regulator of meiotic maturation and euploidy in oocytes, and age-associated MVA pathway abnormalities contribute to oocyte meiotic defects and aneuploidy.

Innate Immune Training Enhances the Reactivation of Latently Infected HIV-1 from Monocytic Cell lines

Abstract HIV virus can persist in a latent but activatable chronic state in resting CD4 +T-cells and macrophages that are more persistent, leading to the requirement of lifelong combination antiretroviral therapy (cART). The latency of HIV-1 in macrophage cells is associated with increased chromatin condensation induced by histone methylation at HIV-1 integration sites. Innate immune training of macrophages has been shown to relieve chromosome condensation through epigenetic rewiring. We hypothesized that training of macrophages could enhance the reactivation of HIV-1 by opening the chromatin to facilitate transcription in response to Latency Reversing Agents (LRAs). We used beta-glucan, Syk inhibitor and Rutaecarpine to train the THP89GFP cell line, which is an experimental model for latently infected HIV-1 monocytes. We found that these trained THP89GFP cells have higher transcription of HIV-1 specific genes in response to PMA stimulation. To check the epigenetic changes associated with training in the proviral HIV-1 DNA of THP89GFP, we performed a chromatin immunoprecipitation for the histone mark, H3K27Ac. Consistent with the higher induction of transcription of HIV-1 genes, we observed that multiple regions of the HIV-1 LTR had higher deposition of H3K27Ac in the trained macrophages. Our studies thus show that induction of trained innate immunity may be a viable approach to the reactivation of latently infected HIV-1. This finding supports the hypothesis that innate immune training stimuli could be developed as novel candidates for enhancing reactivation of latently infected HIV-1, which may facilitate elimination of macrophage reservoirs. This work was supported by the Intramural Research Program of NIAID, NIH This work was supported by the Intramural Research Program of NIAID, NIH and Office of AIDS research.

Identification of Potential Biomarkers in Stomach Adenocarcinoma using Machine Learning Approaches

Background: Stomach adenocarcinoma (STAD) is a common cancer with poor clinical outcomes globally. Due to a lack of early diagnostic markers of disease, the majority of patients are diagnosed at an advanced stage. Objective: The aim of the present study is to provide some new insights into the available biomarkers for patients with STAD using bioinformatics. Methods: RNA-Sequencing and other relevant data of patients with STAD from The Cancer Genome Atlas (TCGA) database were evaluated to identify differentially expressed genes (DEGs). Then, Machine Learning algorithms were undertaken to predict biomarkers. Additionally, Kaplan–Meier analysis was used to detect prognostic biomarkers. Furthermore, the Gene Ontology and Reactome pathways, protein-protein interactions (PPI), multiple sequence alignment, phylogenetic mapping, and correlation between clinical parameters were evaluated. Results: The results showed 61 DEGs, and the key dysregulated genes associated with STAD are MTHFD1L (Methylenetetrahydrofolate dehydrogenase 1-like), ZWILCH (Zwilch Kinetochore Protein), RCC2 (Regulator of chromosome condensation 2), DPT (Dermatopontin), GCOM1 (GRINL1A complex locus 1), and CLEC3B (C-Type Lectin Domain Family 3 Member B). Moreover, the survival analysis reported ASPA (Aspartoacylase) as a prognostic marker. Conclusion: Our study provides a proof of concept of the potential value of ASPA as a prognostic factor in STAD, requiring further functional investigations to explore the value of emerging markers.

RENEB Inter-Laboratory Comparison 2021: Inter-Assay Comparison of Eight Dosimetry Assays.

Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.

A model for Scc2p stimulation of cohesin's ATPase and its inhibition by acetylation of Smc3p.

The evolutionarily conserved cohesin complex mediates sister chromatid cohesion and facilitates mitotic chromosome condensation, DNA repair, and transcription regulation. These biological functions require cohesin's two ATPases, formed by the Smc1p and Smc3p subunits. Cohesin's ATPase activity is stimulated by the Scc2p auxiliary factor. This stimulation is inhibited by Eco1p acetylation of Smc3p at an interface with Scc2p. It was unclear how cohesin's ATPase activity is stimulated by Scc2p or how acetylation inhibits Scc2p, given that the acetylation site is distal to cohesin's ATPase active sites. Here, we identify mutations in budding yeast that suppressed the in vivo defects caused by Smc3p acetyl-mimic and acetyl-defective mutations. We provide compelling evidence that Scc2p activation of cohesin ATPase depends on an interface between Scc2p and a region of Smc1p proximal to cohesin's Smc3p ATPase active site. Furthermore, substitutions at this interface increase or decrease ATPase activity to overcome ATPase modulation by acetyl-mimic and acetyl-null mutations. Using these observations and an existing cryo-EM structure, we propose a model for regulating cohesin ATPase activity. We suggest that Scc2p binding to Smc1p causes the adjacent Smc1p residues and ATP to shift, stimulating Smc3p's ATPase. This stimulatory shift is inhibited through acetylation of the distal Scc2p-Smc3p interface.

Enhanced mitotic arrest and chromosome resolution for cytogenetic analysis in the eastern mosquitofish, Gambusia holbrooki

Maximising the number of cells arrested at metaphase and their resolution is fundamentally important for molecular cytogenetic investigations, particularly in fish, which typically yield low mitotic index and have highly condensed chromosomes. To overcome these limitations, fish were injected with a mitotic stimulator (the yeast, Saccharomyces cerevisiae) to improve the mitotic index, and the intercalating agent ethidium bromide to produce elongated chromosomes. Specifically, adults were injected with activated yeast and then Colcemid (0.025 µg/µl solution, 10 µl per 1 g of body weight) at 24–96 h post yeast injections, followed by chromosome preparations from multiple tissues. Results showed that gill tissue had the highest number of dividing cells at 72 h post yeast exposure with no significant (p > 0.05) differences between the sexes. Nonetheless, sex-specific differences in the mitotic index were observed in spleen, kidney, and liver, which may be attributed to sex-specific differences in immune responses. For elongation of mitotic chromosomes, individuals (both sexes) were first injected with activated yeast and after 48 h with ethidium bromide (2 or 4 µg/ml) and Colcemid (0.05 µg/µl solution, 10 µl per 1 g of body weight). Following which, animals were sampled at three time points (1, 4 and 8 h) for chromosome preparations. The results show that the optimum elongation of metaphase chromosomes of males and females was achieved by using 2 µg/ml and 4 µg/ml, respectively, for 1 h. Interestingly, the average mitotic chromosome length (μm) of males and females post-ethidium bromide exposure was significantly different (p < 0.05) for both concentrations, except at 1 h exposure for 2 µg/ml EtBr. Such differences can be attributed to overall chromosomal condensation differences between sexes. Regardless, the increased mitotic index and chromosome resolution could benefit cytogenetic studies in other fish species.

Over-expression of RRM2 predicts adverse prognosis correlated with immune infiltrates: A potential biomarker for hepatocellular carcinoma.

Ribonucleotide reductase regulatory subunit M2 (RRM2) has been reported to be an oncogene in some malignant tumors, such as lung adenocarcinoma, oral squamous cell carcinoma, glioblastoma, and breast cancer. However, the clinical significance of RRM2 in hepatocellular carcinoma has been less studied. The aim of this study was to assess the importance of RRM2 in hepatocellular carcinoma (HCC) based on the Cancer Genome Atlas (TCGA) database. The RRM2 expression levels and clinical features were downloaded from the TCGA database. Immunohistochemistry results between tumor tissues and normal tissues were downloaded from the Proteinatlas database. Meanwhile, the expression levels of RRM2 in tumor and paraneoplastic tissues were further verified by qRT-PCR and Western Blotting. Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein-interactions (PPI) network were constructed to analyze RRM2-related downstream molecules. In addition, RRM2 expression-related pathways performed by gene set enrichment analysis (GSEA). Association analysis of RRM2 gene expression and immune infiltration was performed by single-sample GSEA (ssGSEA). The RRM2 expression level in tumor tissues was higher than normal tissues (P <0.001). The elevated expression of RRM2 in HCC was significantly correlated with T stage (P <0.05), pathologic stage (P <0.05), tumor status (P <0.05), histologic grade (P<0.001), and AFP (P <0.001). HCC with higher RRM2 expression was positively associated with worse OS (overall survival), PFS (progression-free survival), and DSS (disease-specific survival). In the univariate analysis, the expression of RRM2, T stage, M stage, pathologic stage, and tumor status were negatively correlated with OS (P <0.05). Further analysis using multivariate Cox regression showed that tumor status (P<0.01) and RRM2 expression (P<0.05) were independent prognostic factors of OS in HCC. GO/KEGG analysis showed that the critical biological process (chromosome condensation and p53 signaling pathway) might be the possible function mechanism in promoting HCC. Moreover, GSEA showed that several pathways were enriched in RRM2 high-expression samples, including PD-1 signaling, cell cycle, P27 pathway, and T cell receptor signaling pathway. RRM2 was significantly correlated with the infiltration level of CD8 T cells, Cytotoxic cells, DCs, Neutrophils, NK cells, and T helper cells (P <0.05). Over-expression of RRM2 predict adverse prognosis and is correlated with immune infiltrates in HCC. RRM2 may be a significant molecular biomarker for HCC diagnosis and prognosis.

Exploration of Antiproliferative Activity and Apoptosis Induction of New Nickel(II) Complexes Encompassing Carbazole Ligands.

To attest the effectiveness of nickel complexes as anticancer drug candidates with minimum side effects, the present investigation describes the facile synthesis and anticancer activities of nickel(II) complexes enriched with three derivatives of carbazolone-based benzhydrazone ligands(L) having a [Ni(L)2] composition. Analytical and spectral techniques were used to characterize the synthesized Ni(II) complexes. The single-crystal X-ray diffraction performed for complex 4 confirmed the square planar geometry with a [Ni(κ2-N,O-L)2] arrangement. The MTT assay was carried out for the complexes to determine in vitro cytotoxicity against cancerous human-cervical carcinoma, human-colon carcinoma, and non-cancerous L929 (fibroblast) cells. All three complexes exhibited good toxicity against the cancer cells with a low IC50 concentration. Complex 4, containing -OCH3 fragment, exhibits high lipophilicity and revealed exceptional cytotoxicity against cancer cells. AO-EB fluorescent staining indicated apoptosis-associated cell morphological changes after exposure to complex 4. The apoptosis induction was further confirmed by a HOECHST-33342 fluorescent staining technique via chromosomal condensation and nuclear fragmentation. Further, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) mechanistic studies revealed that complex 4 can raise ROS levels and reduce MMP and promote mitochondrial dysfunction-mediated apoptotic cell death. Further, stimulation of late apoptosis by complex 4 in cervical cancer cells was quantitatively differentiated through the staining of phosphatidylserine externalization by flow cytometry. Furthermore, the ELISA analysis confirmed that complex 4 induced apoptosis through caspase activation.

High Resolution and Automatable Cytogenetic Biodosimetry Using In Situ Telomere and Centromere Hybridization for the Accurate Detection of DNA Damage: An Overview.

In the event of a radiological or nuclear accident, or when physical dosimetry is not available, the scoring of radiation-induced chromosomal aberrations in lymphocytes constitutes an essential tool for the estimation of the absorbed dose of the exposed individual and for effective triage. Cytogenetic biodosimetry employs different cytogenetic assays including the scoring of dicentrics, micronuclei, and translocations as well as analyses of induced premature chromosome condensation to define the frequency of chromosome aberrations. However, inherent challenges using these techniques include the considerable time span from sampling to result, the sensitivity and specificity of the various techniques, and the requirement of highly skilled personnel. Thus, techniques that obviate these challenges are needed. The introduction of telomere and centromere (TC) staining have successfully met these challenges and, in addition, greatly improved the efficiency of cytogenetic biodosimetry through the development of automated approaches, thus reducing the need for specialized personnel. Here, we review the role of the various cytogenetic dosimeters and their recent improvements in the management of populations exposed to genotoxic agents such as ionizing radiation. Finally, we discuss the emerging potentials to exploit these techniques in a wider spectrum of medical and biological applications, e.g., in cancer biology to identify prognostic biomarkers for the optimal triage and treatment of patients.

Monitoring the compaction of single DNA molecules in Xenopus egg extract in real time

DNA compaction is required for the condensation and resolution of chromosomes during mitosis, but the relative contribution of individual chromatin factors to this process is poorly understood. We developed a physiological, cell-free system using high-speed Xenopus egg extracts and optical tweezers to investigate real-time mitotic chromatin fiber formation and force-induced disassembly on single DNA molecules. Compared to interphase extract, which compacted DNA by ~60%, metaphase extract reduced DNA length by over 90%, reflecting differences in whole-chromosome morphology under these two conditions. Depletion of the core histone chaperone ASF1, which inhibits nucleosome assembly, decreased the final degree of metaphase fiber compaction by 29%, while depletion of linker histone H1 had a greater effect, reducing total compaction by 40%. Compared to controls, both depletions reduced the rate of compaction, led to more short periods of decompaction, and increased the speed of force-induced fiber disassembly. In contrast, depletion of condensin from metaphase extract strongly inhibited fiber assembly, resulting in transient compaction events that were rapidly reversed under high force. Altogether, these findings support a speculative model in which condensin plays the predominant role in mitotic DNA compaction, while core and linker histones act to reduce slippage during loop extrusion and modulate the degree of DNA compaction.

Conservative Protein RCC1 Is a New Component of Black Bands of &lt;i&gt;Drosophila&lt;/i&gt; &lt;i&gt;melanogaster&lt;/i&gt; Polytene Chromosomes

Previously, the RCC1 gene (Regulator of Chromosome Сondensation 1) was characterized, which is considered a regulator of chromosome condensation in the cell cycle. This gene encodes a nuclear protein whose amino acid sequence is highly conserved among all eukaryotes and consists of seven repeating units. We have shown that all the most prominent black bands of polytene chromosomes (about 250) and the chromocenter bind antibodies to this protein. We found that antibodies to the xenopus RCC1 protein specifically bind to the Drosophila and human RCC1 protein, while in Drosophila lines with under replication suppression, the relative amount of the RCC1 protein increases compared to the wild type.

Genome-Wide Identification and Expression Analysis of RCC1 Gene Family under Abiotic Stresses in Rice (Oryza sativa L.)

In plants, the essential roles played by the regulator of chromosome condensation 1 (RCC1) in diverse biological processes, including UV-B (ultraviolet-B radiation) response, hormonal signal transduction, cold tolerance and phenotypic plasticity, have been identified. No comprehensive study on the evolution and function of RCC1 gene family in rice has been carried out. A genome-wide analysis of this gene family is thus required. In this study, a total of 26 OsRCC1s unevenly distributed across 10 chromosomes were identified in rice. Based on their phylogenetic relationship and sequence composition, the OsRCC1 family could be classified into six groups. Members within the same group share a similar gene structure and protein motif/domain composition. Gene duplication analysis revealed that segmental duplication might be the main contributor to the expansion of the RCC1 gene family in rice. Several cis-regulatory elements (CREs) relevant to light, abscisic acid (ABA) and methyl jasmonate (MeJA) are abundant in the promoters of OsRCC1s. A large number of microRNA (miRNA) target sites were present in OsRCC1 mRNAs. Additionally, we used data from gene microarray and qRT-PCR to analyze the expression of OsRCC1 genes during various developmental stages and under abiotic stress conditions. OsRCC1s were found to be highly expressed in panicles and seeds, and most OsRCC1s were differentially expressed under abiotic stresses. Taken together, our study provides a systematic characterization of OsRCC1s and preliminarily explores their diversity as well as their biological functions. Evidence demonstrates that OsRCC1s may play vital roles in both development and abiotic stress response. The results presented here lay a foundation for further investigating the functions of OsRCC1s.