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Erenpreisa J, Krigerts J, Salmina K, Gerashchenko BI, Freivalds T, Kurg R, Winter R, Krufczik M, Zayakin P, Hausmann M, Giuliani A. Heterochromatin Networks: Topology, Dynamics, and Function (a Working Hypothesis). Cells 2021; 10:1582. [PMID: 34201566 PMCID: PMC8304199 DOI: 10.3390/cells10071582] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 12/21/2022] Open
Abstract
Open systems can only exist by self-organization as pulsing structures exchanging matter and energy with the outer world. This review is an attempt to reveal the organizational principles of the heterochromatin supra-intra-chromosomal network in terms of nonlinear thermodynamics. The accessibility of the linear information of the genetic code is regulated by constitutive heterochromatin (CHR) creating the positional information in a system of coordinates. These features include scale-free splitting-fusing of CHR with the boundary constraints of the nucleolus and nuclear envelope. The analysis of both the literature and our own data suggests a radial-concentric network as the main structural organization principle of CHR regulating transcriptional pulsing. The dynamic CHR network is likely created together with nucleolus-associated chromatin domains, while the alveoli of this network, including springy splicing speckles, are the pulsing transcription hubs. CHR contributes to this regulation due to the silencing position variegation effect, stickiness, and flexible rigidity determined by the positioning of nucleosomes. The whole system acts in concert with the elastic nuclear actomyosin network which also emerges by self-organization during the transcriptional pulsing process. We hypothesize that the the transcriptional pulsing, in turn, adjusts its frequency/amplitudes specified by topologically associating domains to the replication timing code that determines epigenetic differentiation memory.
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Affiliation(s)
- Jekaterina Erenpreisa
- Latvian Biomedicine Research and Study Centre, LV-1067 Riga, Latvia; (J.K.); (K.S.); (P.Z.)
| | - Jekabs Krigerts
- Latvian Biomedicine Research and Study Centre, LV-1067 Riga, Latvia; (J.K.); (K.S.); (P.Z.)
| | - Kristine Salmina
- Latvian Biomedicine Research and Study Centre, LV-1067 Riga, Latvia; (J.K.); (K.S.); (P.Z.)
| | - Bogdan I. Gerashchenko
- R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology, National Academy of Sciences of Ukraine, 03022 Kyiv, Ukraine;
| | - Talivaldis Freivalds
- Institute of Cardiology and Regenerative Medicine, University of Latvia, LV-1004 Riga, Latvia;
| | - Reet Kurg
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia;
| | - Ruth Winter
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany; (R.W.); (M.K.); (M.H.)
| | - Matthias Krufczik
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany; (R.W.); (M.K.); (M.H.)
| | - Pawel Zayakin
- Latvian Biomedicine Research and Study Centre, LV-1067 Riga, Latvia; (J.K.); (K.S.); (P.Z.)
| | - Michael Hausmann
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany; (R.W.); (M.K.); (M.H.)
| | - Alessandro Giuliani
- Istituto Superiore di Sanita Environment and Health Department, 00161 Roma, Italy
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Krigerts J, Salmina K, Freivalds T, Zayakin P, Rumnieks F, Inashkina I, Giuliani A, Hausmann M, Erenpreisa J. Differentiating cancer cells reveal early large-scale genome regulation by pericentric domains. Biophys J 2021; 120:711-724. [PMID: 33453273 PMCID: PMC7896032 DOI: 10.1016/j.bpj.2021.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 12/30/2020] [Accepted: 01/07/2021] [Indexed: 02/07/2023] Open
Abstract
Finding out how cells prepare for fate change during differentiation commitment was our task. To address whether the constitutive pericentromere-associated domains (PADs) may be involved, we used a model system with known transcriptome data, MCF-7 breast cancer cells treated with the ErbB3 ligand heregulin (HRG), which induces differentiation and is used in the therapy of cancer. PAD-repressive heterochromatin (H3K9me3), centromere-associated-protein-specific, and active euchromatin (H3K4me3) antibodies, real-time PCR, acridine orange DNA structural test (AOT), and microscopic image analysis were applied. We found a two-step DNA unfolding after 15–20 and 60 min of HRG treatment, respectively. This behavior was consistent with biphasic activation of the early response genes (c-fos - fosL1/myc) and the timing of two transcriptome avalanches reported in the literature. In control, the average number of PADs negatively correlated with their size by scale-free distribution, and centromere clustering in turn correlated with PAD size, both indicating that PADs may create and modulate a suprachromosomal network by fusing and splitting a constant proportion of the constitutive heterochromatin. By 15 min of HRG treatment, the bursting unraveling of PADs from the nucleolus boundary occurred, coinciding with the first step of H3K4me3 chromatin unfolding, confirmed by AOT. The second step after 60 min of HRG treatment was associated with transcription of long noncoding RNA from PADs and peaking of fosL1/c-myc response. We hypothesize that the bursting of PAD clusters under a critical silencing threshold pushes the first transcription avalanche, whereas the destruction of the PAD network enables genome rewiring needed for differentiation repatterning, mediated by early response bivalent genes.
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Affiliation(s)
- Jekabs Krigerts
- Latvian Biomedicine Research and Study Centre, Riga, Latvia; University of Latvia, Riga, Latvia
| | | | - Talivaldis Freivalds
- Institute of Cardiology and Regenerative Medicine, University of Latvia, Riga, Latvia
| | - Pawel Zayakin
- Latvian Biomedicine Research and Study Centre, Riga, Latvia
| | - Felikss Rumnieks
- Latvian Biomedicine Research and Study Centre, Riga, Latvia; University of Latvia, Riga, Latvia
| | - Inna Inashkina
- Latvian Biomedicine Research and Study Centre, Riga, Latvia
| | - Alessandro Giuliani
- Environment and Health Department, Italian National Institute of Health, Rome, Italy
| | - Michael Hausmann
- Kirchhoff Institute for Physics, Heidelberg University, Heidelberg, Germany.
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Gerashchenko BI, Salmina K, Krigerts J, Erenpreisa J, Babsky AM. INDUCED POLYPLOIDY AND SORTING OF DAMAGED DNA BY MICRONUCLEATION IN RADIORESISTANT RAT LIVER EPITHELIAL STEM-LIKE CELLS EXPOSED TO X-RAYS. Probl Radiac Med Radiobiol 2020; 24:220-234. [PMID: 31841469 DOI: 10.33145/2304-8336-2019-24-220-234] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Rat liver stem-like epithelial cells (WB-F344) that under certain conditions may differentiate into hepa- tocyte and biliary lineages were subjected to acute X-irradiation with the aim to examine cell cycle peculiarities dur- ing the course of survival. MATERIALS AND METHODS Suspensions of WB-F344 cells that grew as a monolayer and reached sub-confluence were irradiated with 1, 5, and 10 Gy of X-rays (2 Gy/min). As an intact control, sham-irradiated cells were used. After irra- diation, cells were plated into 25-cm2 tissue culture flasks to culture them for over several days without reaching contact inhibition. On days 1, 2, 3, and 5 post-irradiation, cells were harvested and examined for nuclear morpholo- gy and DNA ploidy by stoichiometric toluidine blue reaction and image cytometry. On days 7 and 9 post-irradiation, only heavily irradiated (10 Gy) cells were examined. Also, 10 Gy-irradiated cells were chosen for immunofluorescence staining to monitor persistence of DNA lesions (γ-H2AX), cell proliferation (Ki-67), and self-renewal factors charac- teristic for stem cells (OCT4 and NANOG). RESULTS Radioresistance of WB-F344 cells was evidenced by the findings that they do not undergo rapid and mas- sive cell death that in fact was weakly manifested as apoptotic even in heavily irradiated cells. Instead, there was cell cycle progression delay accompanied by polyploidization (via Ki-67-positive mitotic slippage or via impaired cytokinesis) and micronucleation in a dose-dependent manner, although micronucleation to some extent went ahead of polyploidization. Polyploid cells amenable for recovering from DNA damage can mitotically depolyploidize. Many micronuclei contained γ-H2AX clusters, suggesting isolation of severely damaged DNA fragments. Both factors, OCT4 and NANOG, were expressed in the intact control, but became enhanced after irradiation. CONCLUSIONS Although the fact of micronucleation is indicative of genotoxic effect, WB-F344 cells can probably escape cell death via sorting of damaged DNA by micronuclei. Induction of polyploidy in these cells can be adaptive to promote cell survival and tissue regeneration with possible involvement of self-renewal mechanism.
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Affiliation(s)
- B I Gerashchenko
- R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology, National Academy of Sciences of Ukraine, 45 Vasylkivska St., Kyiv, 03022, Ukraine
| | - K Salmina
- Latvian Biomedical Research and Study Centre, 1 Ratsupites St., Riga, LV-1067, Latvia
| | - J Krigerts
- Latvian Biomedical Research and Study Centre, 1 Ratsupites St., Riga, LV-1067, Latvia
| | - J Erenpreisa
- Latvian Biomedical Research and Study Centre, 1 Ratsupites St., Riga, LV-1067, Latvia
| | - A M Babsky
- Ivan Franko National University of Lviv, Faculty of Biology, 4 Mykhaila Hrushevskoho St., Lviv, 79005, Ukraine
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Erenpreisa J, Krigerts J, Salmina K, Selga T, Sorokins H, Freivalds T. Differential staining of peripheral nuclear chromatin with Acridine orange implies an A-form epichromatin conformation of the DNA. Nucleus 2019; 9:171-181. [PMID: 29363398 PMCID: PMC5973139 DOI: 10.1080/19491034.2018.1431081] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The chromatin observed by conventional electron microscopy under the nuclear envelope constitutes a single layer of dense 30–35 nm granules, while ∼30 nm fibrils laterally attached to them, form large patches of lamin-associated domains (LADs). This particular surface “epichromatin” can be discerned by specific (H2A+H2B+DNA) conformational antibody at the inner nuclear envelope and around mitotic chromosomes. In order to differentiate the DNA conformation of the peripheral chromatin we applied an Acridine orange (AO) DNA structural test involving RNAse treatment and the addition of AO after acid pre-treatment. MCF-7 cells treated in this way revealed yellow/red patches of LADs attached to a thin green nuclear rim and with mitotic chromosomes outlined in green, topologically corresponding to epichromatin epitope staining by immunofluorescence. Differentially from LADs, the epichromatin was unable to provide metachromatic staining by AO, unless thermally denatured at 94oC. DNA enrichment in GC stretches has been recently reported for immunoprecipitated ∼ 1Kb epichromatin domains. Together these data suggest that certain epichromatin segments assume the relatively hydrophobic DNA A-conformation at the nuclear envelope and surface of mitotic chromosomes, preventing AO side dimerisation. We hypothesize that epichromatin domains form nucleosome superbeads. Hydrophobic interactions stack these superbeads and align them at the nuclear envelope, while repulsing the hydrophilic LADs. The hydrophobicity of epichromatin explains its location at the surface of mitotic chromosomes and its function in mediating chromosome attachment to the restituting nuclear envelope during telophase.
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Affiliation(s)
| | - Jekabs Krigerts
- a Latvian Biomedical Research & Study Centre , Ratsupites 1, Riga , Latvia.,b Institute of Biomedical Engineering and Nanotechnologies, Riga Technical University , Kalku iela 1, Riga , Latvia
| | - Kristine Salmina
- a Latvian Biomedical Research & Study Centre , Ratsupites 1, Riga , Latvia
| | - Turs Selga
- c Faculty of Biology, University of Latvia , Raina bulvaris 19, Riga , Latvia
| | - Hermanis Sorokins
- b Institute of Biomedical Engineering and Nanotechnologies, Riga Technical University , Kalku iela 1, Riga , Latvia
| | - Talivaldis Freivalds
- d Institute of Kardiology and Regenerative Medicine, University of Latvia , Raina bulvaris 19, Riga , Latvia
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Salmina K, Huna A, Inashkina I, Belyayev A, Krigerts J, Pastova L, Vazquez-Martin A, Erenpreisa J. Nucleolar aggresomes mediate release of pericentric heterochromatin and nuclear destruction of genotoxically treated cancer cells. Nucleus 2017; 8:205-221. [PMID: 28068183 DOI: 10.1080/19491034.2017.1279775] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The role of the nucleolus and autophagy in maintenance of nuclear integrity is poorly understood. In addition, the mechanisms of nuclear destruction in cancer cells senesced after conventional chemotherapy are unclear. In an attempt to elucidate these issues, we studied teratocarcinoma PA1 cells treated with Etoposide (ETO), focusing on the nucleolus. Following treatment, most cells enter G2 arrest, display persistent DNA damage and activate p53, senescence, and macroautophagy markers. 2-5 µm sized nucleolar aggresomes (NoA) containing fibrillarin (FIB) and damaged rDNA, colocalized with ubiquitin, pAMPK, and LC3-II emerge, accompanied by heterochromatin fragments, when translocated perinuclearly. Microscopic counts following application of specific inhibitors revealed that formation of FIB-NoA is dependent on deficiency of the ubiquitin proteasome system coupled to functional autophagy. In contrast, the accompanying NoAs release of pericentric heterochromatin, which exceeds their frequency, is favored by debilitation of autophagic flux. Potential survivors release NoA in the cytoplasm during rare mitoses, while exit of pericentric fragments often depleted of H3K9Me3, with or without encompassing by NoA, occurs through the nucleolar protrusions and defects of the nuclear envelope. Foci of LC3-II are accumulated in the nucleoli undergoing cessation of rDNA transcription. As an origin of heterochromatin fragmentation, the unscheduled DNA synthesis and circular DNAs were found in the perinucleolar heterochromatin shell, along with activation and retrotransposition of ALU elements, colocalized with 45S rDNA in NoAs. The data indicate coordination of the basic nucleolar function with autophagy regulation in maintenance of the integrity of the nucleolus associated domains secured by inactivity of retrotransposons.
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Affiliation(s)
| | - Anda Huna
- a Latvian Biomedical Research & Study Centre , Riga , Latvia
| | - Inna Inashkina
- a Latvian Biomedical Research & Study Centre , Riga , Latvia
| | - Alexander Belyayev
- b Botanical Institute AS CR , Czech Academy of Science , Prague, Czech Republic
| | - Jekabs Krigerts
- a Latvian Biomedical Research & Study Centre , Riga , Latvia
| | - Ladislava Pastova
- b Botanical Institute AS CR , Czech Academy of Science , Prague, Czech Republic
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Huna A, Salmina K, Erenpreisa J, Vazquez-Martin A, Krigerts J, Inashkina I, Gerashchenko BI, Townsend PA, Cragg MS, Jackson TR. Role of stress-activated OCT4A in the cell fate decisions of embryonal carcinoma cells treated with etoposide. Cell Cycle 2015; 14:2969-84. [PMID: 26102294 PMCID: PMC4825594 DOI: 10.1080/15384101.2015.1056948] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Tumor cellular senescence induced by genotoxic treatments has recently been found to be paradoxically linked to the induction of “stemness.” This observation is critical as it directly impinges upon the response of tumors to current chemo-radio-therapy treatment regimens. Previously, we showed that following etoposide (ETO) treatment embryonal carcinoma PA-1 cells undergo a p53-dependent upregulation of OCT4A and p21Cip1 (governing self-renewal and regulating cell cycle inhibition and senescence, respectively). Here we report further detail on the relationship between these and other critical cell-fate regulators. PA-1 cells treated with ETO display highly heterogeneous increases in OCT4A and p21Cip1 indicative of dis-adaptation catastrophe. Silencing OCT4A suppresses p21Cip1, changes cell cycle regulation and subsequently suppresses terminal senescence; p21Cip1-silencing did not affect OCT4A expression or cellular phenotype. SOX2 and NANOG expression did not change following ETO treatment suggesting a dissociation of OCT4A from its pluripotency function. Instead, ETO-induced OCT4A was concomitant with activation of AMPK, a key component of metabolic stress and autophagy regulation. p16ink4a, the inducer of terminal senescence, underwent autophagic sequestration in the cytoplasm of ETO-treated cells, allowing alternative cell fates. Accordingly, failure of autophagy was accompanied by an accumulation of p16ink4a, nuclear disintegration, and loss of cell recovery. Together, these findings imply that OCT4A induction following DNA damage in PA-1 cells, performs a cell stress, rather than self-renewal, function by moderating the expression of p21Cip1, which alongside AMPK helps to then regulate autophagy. Moreover, this data indicates that exhaustion of autophagy, through persistent DNA damage, is the cause of terminal cellular senescence.
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Affiliation(s)
- Anda Huna
- a Latvian Biomedical Research and Study Center ; Riga, Latvia
| | | | | | | | - Jekabs Krigerts
- a Latvian Biomedical Research and Study Center ; Riga, Latvia
| | - Inna Inashkina
- a Latvian Biomedical Research and Study Center ; Riga, Latvia
| | - Bogdan I Gerashchenko
- a Latvian Biomedical Research and Study Center ; Riga, Latvia.,d R. E. Kavetsky Institute of Experimental Pathology; Oncology and Radiobiology; National Academy of Sciences of Ukraine ; Kyiv , Ukraine
| | - Paul A Townsend
- b Institute of Cancer Sciences; Manchester Cancer Research Center; University of Manchester; Manchester Academic Health Science Center ; Manchester , UK
| | - Mark S Cragg
- c Cancer Sciences Unit; University of Southampton; Faculty of Medicine; General Hospital ; Southampton , UK
| | - Thomas R Jackson
- b Institute of Cancer Sciences; Manchester Cancer Research Center; University of Manchester; Manchester Academic Health Science Center ; Manchester , UK
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