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Thakur BL, Ray A, Redon CE, Aladjem MI. Preventing excess replication origin activation to ensure genome stability. Trends Genet 2022; 38:169-181. [PMID: 34625299 PMCID: PMC8752500 DOI: 10.1016/j.tig.2021.09.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/14/2021] [Accepted: 09/16/2021] [Indexed: 02/03/2023]
Abstract
Cells activate distinctive regulatory pathways that prevent excessive initiation of DNA replication to achieve timely and accurate genome duplication. Excess DNA synthesis is constrained by protein-DNA interactions that inhibit initiation at dormant origins. In parallel, specific modifications of pre-replication complexes prohibit post-replicative origin relicensing. Replication stress ensues when the controls that prevent excess replication are missing in cancer cells, which often harbor extrachromosomal DNA that can be further amplified by recombination-mediated processes to generate chromosomal translocations. The genomic instability that accompanies excess replication origin activation can provide a promising target for therapeutic intervention. Here we review molecular pathways that modulate replication origin dormancy, prevent excess origin activation, and detect, encapsulate, and eliminate persistent excess DNA.
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Affiliation(s)
- Bhushan L Thakur
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Anagh Ray
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Christophe E Redon
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.
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2
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Origin of Genome Instability and Determinants of Mutational Landscape in Cancer Cells. Genes (Basel) 2020; 11:genes11091101. [PMID: 32967144 PMCID: PMC7563369 DOI: 10.3390/genes11091101] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 09/12/2020] [Accepted: 09/18/2020] [Indexed: 12/31/2022] Open
Abstract
Genome instability is a crucial and early event associated with an increased predisposition to tumor formation. In the absence of any exogenous agent, a single human cell is subjected to about 70,000 DNA lesions each day. It has now been shown that physiological cellular processes including DNA transactions during DNA replication and transcription contribute to DNA damage and induce DNA damage responses in the cell. These processes are also influenced by the three dimensional-chromatin architecture and epigenetic regulation which are altered during the malignant transformation of cells. In this review, we have discussed recent insights about how replication stress, oncogene activation, chromatin dynamics, and the illegitimate recombination of cell-free chromatin particles deregulate cellular processes in cancer cells and contribute to their evolution. The characterization of such endogenous sources of genome instability in cancer cells can be exploited for the development of new biomarkers and more effective therapies for cancer treatment.
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3
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Solorza J, Recabarren R, Alzate-Morales J. Molecular Insights into the Trapping Effect of Ca 2+ in Protein Kinase A: A Molecular Dynamics Study. J Chem Inf Model 2020; 60:898-914. [PMID: 31804819 DOI: 10.1021/acs.jcim.9b00857] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Protein kinase A has become a model system for the study of kinases, and therefore, a comprehensive understanding of the underlying molecular mechanisms in its catalytic cycle is of crucial importance. One of the aspects that has received recent attention is the role that metal cofactors play in the catalytic cycle. Although Mg2+ is the well-known physiological ion used by protein kinases, Ca2+ ions can also assist the phosphoryl transfer reaction but with lower catalytic activities. This inhibitory effect has been attributed to the ability of Ca2+ to trap the reaction products at the active site, and it has been proposed as a possible regulatory mechanism of the enzyme. Thus, in order to get a clearer understanding of these molecular events, computational simulations in the product state of PKA, in the presence of Mg2+ and Ca2+ ions, were performed through molecular dynamics (MD). Different protonation states of the active site were considered in order to model the different mechanistic pathways that have been proposed. Our results show that different protonation states of the phosphorylated serine residue at the peptide substrate (pSer21), as well as the protonation state of residue Asp166, can have a marked influence on the flexibility of regions surrounding the active site. This is the case of the glycine-rich loop, a structural motif that is directly involved in the release of the products from the PKA active site. MD simulations were capable to reproduce the crystallographic conformations but also showed other conformations not previously reported in the crystal structures that may be involved in enhancing the affinity of pSP20 to PKA in the presence of Ca2+. Hydrogen bonding interactions at the PKA-pSP20 interface were influenced whether by the protonation state of the active site or by the metal cofactor used by the enzyme. Altogether, our results provide molecular aspects into the inhibitory mechanism of Ca2+ in PKA and suggest which is the most probable protonation state of the phosphorylated product at the active site.
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Affiliation(s)
- Jocelyn Solorza
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile
| | - Rodrigo Recabarren
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile
| | - Jans Alzate-Morales
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile
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4
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CDK1 inhibition facilitates formation of syncytiotrophoblasts and expression of human Chorionic Gonadotropin. Placenta 2018; 66:57-64. [PMID: 29884303 DOI: 10.1016/j.placenta.2018.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 05/05/2018] [Accepted: 05/09/2018] [Indexed: 11/22/2022]
Abstract
AIMS The human placental syncytiotrophoblast (STB) cells play essential roles in embryo implantation and nutrient exchange between the mother and the fetus. STBs are polyploid which are formed by fusion of diploid cytotrophoblast (CTB) cells. Abnormality in STBs formation can result in pregnancy-related disorders. While a number of genes have been associated with CTB fusion the initial events that trigger cell fusion are not well understood. Primary objective of this study was to enhance our understanding about the molecular mechanism of placental cell fusion. METHODS FACS and microscopic analysis was used to optimize Forskolin-induced fusion of BeWo cells (surrogate of CTBs) and subsequently, changes in the expression of different cell cycle regulator genes were analyzed through Western blotting and qPCR. Immunohistochemistry was performed on the first trimester placental tissue sections to validate the results in the context of placental tissue. Effect of Cyclin Dependent Kinase 1 (CDK1) inhibitor, RO3306, on BeWo cell fusion was studied by microscopy and FACS, and by monitoring the expression of human Chorionic Gonadotropin (hCG) by Western blotting and qPCR. RESULTS The data showed that the placental cell fusion was associated with down regulation of CDK1 and its associated cyclin B, and significant decrease in DNA replication. Moreover, inhibition of CDK1 by an exogenous inhibitor induced placental cell fusion and expression of hCG. CONCLUSION Here, we report that the placental cell fusion can be induced by inhibiting CDK1. This study has a high therapeutic significance to manage pregnancy related abnormalities.
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5
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Vassilev A, Lee CY, Vassilev B, Zhu W, Ormanoglu P, Martin SE, DePamphilis ML. Identification of genes that are essential to restrict genome duplication to once per cell division. Oncotarget 2018; 7:34956-76. [PMID: 27144335 PMCID: PMC5085202 DOI: 10.18632/oncotarget.9008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 04/07/2016] [Indexed: 12/02/2022] Open
Abstract
Nuclear genome duplication is normally restricted to once per cell division, but aberrant events that allow excess DNA replication (EDR) promote genomic instability and aneuploidy, both of which are characteristics of cancer development. Here we provide the first comprehensive identification of genes that are essential to restrict genome duplication to once per cell division. An siRNA library of 21,584 human genes was screened for those that prevent EDR in cancer cells with undetectable chromosomal instability. Candidates were validated by testing multiple siRNAs and chemical inhibitors on both TP53+ and TP53- cells to reveal the relevance of this ubiquitous tumor suppressor to preventing EDR, and in the presence of an apoptosis inhibitor to reveal the full extent of EDR. The results revealed 42 genes that prevented either DNA re-replication or unscheduled endoreplication. All of them participate in one or more of eight cell cycle events. Seventeen of them have not been identified previously in this capacity. Remarkably, 14 of the 42 genes have been shown to prevent aneuploidy in mice. Moreover, suppressing a gene that prevents EDR increased the ability of the chemotherapeutic drug Paclitaxel to induce EDR, suggesting new opportunities for synthetic lethalities in the treatment of human cancers.
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Affiliation(s)
- Alex Vassilev
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2753, USA
| | - Chrissie Y Lee
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2753, USA.,Current address: NantBioscience, Culver City, CA 90232, USA
| | - Boris Vassilev
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2753, USA
| | - Wenge Zhu
- Department of Biochemistry and Molecular Biology, George Washington University, Washington DC 20037, USA
| | - Pinar Ormanoglu
- National Center of Advancing Translational Sciences, National Institutes of Health, Rockville, MD 20850, USA
| | - Scott E Martin
- National Center of Advancing Translational Sciences, National Institutes of Health, Rockville, MD 20850, USA.,Current Address: Genentech, Inc., South San Francisco, CA 94080, USA
| | - Melvin L DePamphilis
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2753, USA
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6
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Aladjem MI, Redon CE. Order from clutter: selective interactions at mammalian replication origins. Nat Rev Genet 2017; 18:101-116. [PMID: 27867195 PMCID: PMC6596300 DOI: 10.1038/nrg.2016.141] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mammalian chromosome duplication progresses in a precise order and is subject to constraints that are often relaxed in developmental disorders and malignancies. Molecular information about the regulation of DNA replication at the chromatin level is lacking because protein complexes that initiate replication seem to bind chromatin indiscriminately. High-throughput sequencing and mathematical modelling have yielded detailed genome-wide replication initiation maps. Combining these maps and models with functional genetic analyses suggests that distinct DNA-protein interactions at subgroups of replication initiation sites (replication origins) modulate the ubiquitous replication machinery and supports an emerging model that delineates how indiscriminate DNA-binding patterns translate into a consistent, organized replication programme.
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Affiliation(s)
- Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
| | - Christophe E Redon
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
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7
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Marks AB, Fu H, Aladjem MI. Regulation of Replication Origins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:43-59. [PMID: 29357052 DOI: 10.1007/978-981-10-6955-0_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In eukaryotes, genome duplication starts concomitantly at many replication initiation sites termed replication origins. The replication initiation program is spatially and temporally coordinated to ensure accurate, efficient DNA synthesis that duplicates the entire genome while maintaining other chromatin-dependent functions. Unlike in prokaryotes, not all potential replication origins in eukaryotes are needed for complete genome duplication during each cell cycle. Instead, eukaryotic cells vary the use of initiation sites so that only a fraction of potential replication origins initiate replication each cell cycle. Flexibility in origin choice allows each eukaryotic cell type to utilize different initiation sites, corresponding to unique nuclear DNA packaging patterns. These patterns coordinate replication with gene expression and chromatin condensation. Budding yeast replication origins share a consensus sequence that marks potential initiation sites. Metazoan origins, on the other hand, lack a consensus sequence. Rather, they are associated with a collection of structural features, chromatin packaging features, histone modifications, transcription, and DNA-DNA/DNA-protein interactions. These features confer cell type-specific replication and expression and play an essential role in maintaining genomic stability.
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Affiliation(s)
- Anna B Marks
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA
| | - Haiqing Fu
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA.
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8
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Making Sense of the Tangle: Insights into Chromatin Folding and Gene Regulation. Genes (Basel) 2016; 7:genes7100071. [PMID: 27669308 PMCID: PMC5083910 DOI: 10.3390/genes7100071] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 08/10/2016] [Accepted: 09/07/2016] [Indexed: 01/03/2023] Open
Abstract
Proximity ligation assays such as circularized chromosome conformation capture and high-throughput chromosome capture assays have shed light on the structural organization of the interphase genome. Functional topologically associating domains (TADs) that constitute the building blocks of genomic organization are disrupted and reconstructed during the cell cycle. Epigenetic memory, as well as the sequence of chromosomes, regulate TAD reconstitution. Sub-TAD domains that are invariant across cell types have been identified, and contacts between these domains, rather than looping, are speculated to drive chromatin folding. Replication domains are established simultaneously with TADs during the cell cycle and the two correlate well in terms of characteristic features, such as lamin association and histone modifications. CCCTC-binding factor (CTCF) and cohesin cooperate across different cell types to regulate genes and genome organization. CTCF elements that demarcate TAD boundaries are commonly disrupted in cancer and promote oncogene activation. Chromatin looping facilitates interactions between distant promoters and enhancers, and the resulting enhanceosome complex promotes gene expression. Deciphering the chromatin tangle requires comprehensive integrative analyses of DNA- and protein-dependent factors that regulate genomic organization.
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Zhang Y, Qian D, Li Z, Huang Y, Wu Q, Ru G, Chen M, Wang B. Oxidative stress-induced DNA damage of mouse zygotes triggers G2/M checkpoint and phosphorylates Cdc25 and Cdc2. Cell Stress Chaperones 2016; 21:687-96. [PMID: 27117522 PMCID: PMC4907999 DOI: 10.1007/s12192-016-0693-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 04/06/2016] [Accepted: 04/16/2016] [Indexed: 02/05/2023] Open
Abstract
In vitro fertilized (IVF) embryos show both cell cycle and developmental arrest. We previously showed oxidative damage activates the ATM → Chk1 → Cdc25B/Cdc25C cascade to mediate G2/M cell cycle arrest for repair of hydrogen peroxide (H2O2)-induced oxidative damage in sperm. However, the mechanisms underlying the developmental delay of zygotes are unknown. To develop a model of oxidative-damaged zygotes, we treated mouse zygotes with different concentrations of H2O2 (0, 0.01, 0.02, 0.03, 0.04, 0.05 mM), and evaluated in vitro zygote development, BrdU incorporation to detect the duration of S phase. We also examined reactive oxygen species level and used immunofluorescence to detect activation of γH2AX, Cdc2, and Cdc25. Oxidatively damaged zygotes showed a delay in G2/M phase and produced a higher level of ROS. At the same time, γH2AX was detected in oxidatively damaged zygotes as well as phospho-Cdc25B (Ser323), phospho-Cdc25C (Ser216), and phospho-Cdc2 (Tyr15). Our study indicates that oxidative stress-induced DNA damage of mouse zygotes triggers the cell cycle checkpoint, which results in G2/M cell cycle arrest, and that phospho-Cdc25B (Ser323), phospho-Cdc25C (Ser216), and phospho-Cdc2 (Tyr15) participate in activating the G2/M checkpoint.
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Affiliation(s)
- Yuting Zhang
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
| | - Diting Qian
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
| | - Zhiling Li
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China.
| | - Yue Huang
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
| | - Que Wu
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
| | - Gaizhen Ru
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
| | - Man Chen
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
| | - Bin Wang
- Reproductive Center, The First Affiliated Hospital of Shantou University Medical College, Shantou University, Shantou, Guangdong, People's Republic of China
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Wedelolactone mitigates UVB induced oxidative stress, inflammation and early tumor promotion events in murine skin: plausible role of NFkB pathway. Eur J Pharmacol 2016; 786:253-264. [PMID: 27164422 DOI: 10.1016/j.ejphar.2016.05.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 04/28/2016] [Accepted: 05/04/2016] [Indexed: 11/20/2022]
Abstract
UVB (Ultra-violet B) radiation is one of the major etiological factors in various dermal pathology viz. dermatitis, actinic folliculitis, solar urticaria, psoriasis and cancer among many others. UVB causes toxic manifestation in tissues by inciting inflammatory and tumor promoting events. We have designed this study to assess the anti-inflammatory and anti-tumor promotion effect of Wedelolactone (WDL) a specific IKK inhibitor. Results indicate significant restoration of anti-oxidative enzymes due to WDL treatments. We also found that WDL was effective in mitigating inflammatory markers consisting of MPO (myeloperoxidase), Mast cells trafficking, Langerhans cells suppression and COX 2 expression up regulation due to UVB exposure. We also deduce that WDL presented a promising intervention in attenuating early tumor promotion events caused by UVB exposure as indicated by the results of ODC (Ornithine Decarboxylase), Thymidine assay, Vimentin and VEGF (Vascular-endothelial growth factor) expression. This study was able to provide substantial cues for the therapeutic ability of Wedelolactone against inflammatory and tumor promoting events in murine skin depicting plausible role of NFkB pathway.
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11
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Marks AB, Smith OK, Aladjem MI. Replication origins: determinants or consequences of nuclear organization? Curr Opin Genet Dev 2016; 37:67-75. [PMID: 26845042 PMCID: PMC4914405 DOI: 10.1016/j.gde.2015.11.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 11/24/2015] [Accepted: 11/25/2015] [Indexed: 12/20/2022]
Abstract
Chromosome replication, gene expression and chromatin assembly all occur on the same template, necessitating a tight spatial and temporal coordination to maintain genomic stability. The distribution of replication initiation events is responsive to local and global changes in chromatin structure and is affected by transcriptional activity. Concomitantly, replication origin sequences, which determine the locations of replication initiation events, can affect chromatin structure and modulate transcriptional efficiency. The flexibility observed in the replication initiation landscape might help achieve complete and accurate genome duplication while coordinating the DNA replication program with transcription and other nuclear processes in a cell-type specific manner. This review discusses the relationships among replication origin distribution, local and global chromatin structures and concomitant nuclear metabolic processes.
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Affiliation(s)
- Anna B Marks
- Developmental Therapeutics Branch, NCI, NIH, Bethesda, MD, USA
| | - Owen K Smith
- Developmental Therapeutics Branch, NCI, NIH, Bethesda, MD, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, NCI, NIH, Bethesda, MD, USA.
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12
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Abstract
The mechanism that duplicates the nuclear genome during the trillions of cell divisions required to develop from zygote to adult is the same throughout the eukarya, but the mechanisms that determine where, when and how much nuclear genome duplication occur regulate development and differ among the eukarya. They allow organisms to change the rate of cell proliferation during development, to activate zygotic gene expression independently of DNA replication, and to restrict nuclear DNA replication to once per cell division. They allow specialized cells to exit their mitotic cell cycle and differentiate into polyploid cells, and in some cases, to amplify the number of copies of specific genes. It is genome duplication that drives evolution, by virtue of the errors that inevitably occur when the same process is repeated trillions of times. It is, unfortunately, the same errors that produce age-related genetic disorders such as cancer.
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Affiliation(s)
- Melvin L DePamphilis
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
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13
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14
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Behaegel J, Comet JP, Bernot G, Cornillon E, Delaunay F. A hybrid model of cell cycle in mammals. J Bioinform Comput Biol 2015; 14:1640001. [PMID: 26708052 DOI: 10.1142/s0219720016400011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Time plays an essential role in many biological systems, especially in cell cycle. Many models of biological systems rely on differential equations, but parameter identification is an obstacle to use differential frameworks. In this paper, we present a new hybrid modeling framework that extends René Thomas' discrete modeling. The core idea is to associate with each qualitative state "celerities" allowing us to compute the time spent in each state. This hybrid framework is illustrated by building a 5-variable model of the mammalian cell cycle. Its parameters are determined by applying formal methods on the underlying discrete model and by constraining parameters using timing observations on the cell cycle. This first hybrid model presents the most important known behaviors of the cell cycle, including quiescent phase and endoreplication.
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Affiliation(s)
- Jonathan Behaegel
- * Université Nice-Sophia Antipolis, I3S-UMR CNRS 7271, CS 40121, 06903 Sophia Antipolis Cedex, France
| | - Jean-Paul Comet
- * Université Nice-Sophia Antipolis, I3S-UMR CNRS 7271, CS 40121, 06903 Sophia Antipolis Cedex, France
| | - Gilles Bernot
- * Université Nice-Sophia Antipolis, I3S-UMR CNRS 7271, CS 40121, 06903 Sophia Antipolis Cedex, France
| | - Emilien Cornillon
- * Université Nice-Sophia Antipolis, I3S-UMR CNRS 7271, CS 40121, 06903 Sophia Antipolis Cedex, France
| | - Franck Delaunay
- † Université Nice Sophia Antipolis, CNRS UMR7277, INSERM U1091, Institut de Biologie Valrose, 06108 Nice, France
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15
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Gergics P, Brinkmeier ML, Camper SA. Lhx4 deficiency: increased cyclin-dependent kinase inhibitor expression and pituitary hypoplasia. Mol Endocrinol 2015; 29:597-612. [PMID: 25668206 PMCID: PMC4399274 DOI: 10.1210/me.2014-1380] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/06/2015] [Indexed: 12/30/2022] Open
Abstract
Defects in the Lhx4, Lhx3, and Pitx2 genes can cause combined pituitary hormone deficiency and pituitary hypoplasia in both humans and mice. Not much is known about the mechanism underlying hypoplasia in these mutants beyond generally increased cell death and poorly maintained proliferation. We identified both common and unique abnormalities in developmental regulation of key cell cycle regulator gene expression in each of these three mutants. All three mutants exhibit reduced expression of the proliferative marker Ki67 and the transitional marker p57. We discovered that expression of the cyclin-dependent kinase inhibitor 1a (Cdkn1a or p21) is expanded dorsally in the pituitary primordium of both Lhx3 and Lhx4 mutants. Uniquely, Lhx4 mutants exhibit reduced cyclin D1 expression and have auxiliary pouch-like structures. We show evidence for indirect and direct effects of LHX4 on p21 expression in αT3-1 pituitary cells. In summary, Lhx4 is necessary for efficient pituitary progenitor cell proliferation and restriction of p21 expression.
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Affiliation(s)
- Peter Gergics
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan 48109
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16
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Stephenson R, Hosler MR, Gavande NS, Ghosh AK, Weake VM. Characterization of a Drosophila ortholog of the Cdc7 kinase: a role for Cdc7 in endoreplication independent of Chiffon. J Biol Chem 2014; 290:1332-47. [PMID: 25451925 DOI: 10.1074/jbc.m114.597948] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cdc7 is a serine-threonine kinase that phosphorylates components of the pre-replication complex during DNA replication initiation. Cdc7 is highly conserved, and Cdc7 orthologs have been characterized in organisms ranging from yeast to humans. Cdc7 is activated specifically during late G1/S phase by binding to its regulatory subunit, Dbf4. Drosophila melanogaster contains a Dbf4 ortholog, Chiffon, which is essential for chorion amplification in Drosophila egg chambers. However, no Drosophila ortholog of Cdc7 has yet been characterized. Here, we report the functional and biochemical characterization of a Drosophila ortholog of Cdc7. Co-expression of Drosophila Cdc7 and Chiffon is able to complement a growth defect in yeast containing a temperature-sensitive Cdc7 mutant. Cdc7 and Chiffon physically interact and can be co-purified from insect cells. Cdc7 phosphorylates the known Cdc7 substrates Mcm2 and histone H3 in vitro, and Cdc7 kinase activity is stimulated by Chiffon and inhibited by the Cdc7-specific inhibitor XL413. Drosophila egg chamber follicle cells deficient for Cdc7 have a defect in two types of DNA replication, endoreplication and chorion gene amplification. However, follicle cells deficient for Chiffon have a defect in chorion gene amplification but still undergo endocycling. Our results show that Cdc7 interacts with Chiffon to form a functional Dbf4-dependent kinase complex and that Cdc7 is necessary for DNA replication in Drosophila egg chamber follicle cells. Additionally, we show that Chiffon is a member of an expanding subset of DNA replication initiation factors that are not strictly required for endoreplication in Drosophila.
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Affiliation(s)
| | | | | | - Arun K Ghosh
- Chemistry and Medicinal Chemistry, and Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
| | - Vikki M Weake
- From the Departments of Biochemistry and Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
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Komaki Y, Mariñas BJ, Plewa MJ. Toxicity of drinking water disinfection byproducts: cell cycle alterations induced by the monohaloacetonitriles. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:11662-9. [PMID: 25185076 DOI: 10.1021/es5032344] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Haloacetonitriles (HANs) are a chemical class of drinking water disinfection byproducts (DBPs) that form from reactions between disinfectants and nitrogen-containing precursors, the latter more prevalent in water sources impacted by algae bloom and municipal wastewater effluent discharge. HANs, previously demonstrated to be genotoxic, were investigated for their effects on the mammalian cell cycle. Treating Chinese hamster ovary (CHO) cells with monoHANs followed by the release from the chemical treatment resulted in the accumulation of abnormally high DNA content in cells over time (hyperploid). The potency for the cell cycle alteration followed the order: iodoacetonitrile (IAN) > bromoacetonitrile (BAN) ≫ chloroacetonitrile (CAN). Exposure to 6 μM IAN, 12 μM BAN and 900 μM CAN after 26 h post-treatment incubation resulted in DNA repair; however, subsequent cell cycle alteration effects were observed. Cell proliferation of HAN-treated cells was suppressed for as long as 43 to 52 h. Enlarged cell size was observed after 52 h post-treatment incubation without the induction of cytotoxicity. The HAN-mediated cell cycle alteration was mitosis- and proliferation-dependent, which suggests that HAN treatment induced mitosis override, and that HAN-treated cells proceeded into S phase and directly into the next cell cycle. Cells with multiples genomes would result in aneuploidy (state of abnormal chromosome number and DNA content) at the next mitosis since extra centrosomes could compromise the assembly of bipolar spindles. There is accumulating evidence of a transient tetraploid state proceeding to aneuploidy in cancer progression. Biological self-defense systems to ensure genomic stability and to eliminate tetraploid cells exist in eukaryotic cells. A key tumor suppressor gene, p53, is oftentimes mutated in various types of human cancer. It is possible that HAN disruption of the normal cell cycle and the generation of aberrant cells with an abnormal number of chromosomes may contribute to cancer induction and perhaps be involved in the induction of adverse pregnancy outcomes associated with long-term consumption of disinfected water. Here we present the first observation of the induction of hyperploidy by a class of DBPs.
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Affiliation(s)
- Yukako Komaki
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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Smith OK, Aladjem MI. Chromatin structure and replication origins: determinants of chromosome replication and nuclear organization. J Mol Biol 2014; 426:3330-41. [PMID: 24905010 DOI: 10.1016/j.jmb.2014.05.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 05/22/2014] [Accepted: 05/24/2014] [Indexed: 12/29/2022]
Abstract
The DNA replication program is, in part, determined by the epigenetic landscape that governs local chromosome architecture and directs chromosome duplication. Replication must coordinate with other biochemical processes occurring concomitantly on chromatin, such as transcription and remodeling, to insure accurate duplication of both genetic and epigenetic features and to preserve genomic stability. The importance of genome architecture and chromatin looping in coordinating cellular processes on chromatin is illustrated by two recent sets of discoveries. First, chromatin-associated proteins that are not part of the core replication machinery were shown to affect the timing of DNA replication. These chromatin-associated proteins could be working in concert, or perhaps in competition, with the transcriptional machinery and with chromatin modifiers to determine the spatial and temporal organization of replication initiation events. Second, epigenetic interactions are mediated by DNA sequences that determine chromosomal replication. In this review, we summarize recent findings and current models linking spatial and temporal regulation of the replication program with epigenetic signaling. We discuss these issues in the context of the genome's three-dimensional structure with an emphasis on events occurring during the initiation of DNA replication.
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Affiliation(s)
- Owen K Smith
- DNA Replication Group, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Mirit I Aladjem
- DNA Replication Group, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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Nagpal N, Kulshreshtha R. miR-191: an emerging player in disease biology. Front Genet 2014; 5:99. [PMID: 24795757 PMCID: PMC4005961 DOI: 10.3389/fgene.2014.00099] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 04/07/2014] [Indexed: 12/22/2022] Open
Abstract
Specific microRNAs have emerged as key players in disease biology by playing crucial role in disease development and progression. This review draws attention to one such microRNA, miR-191 that has been recently reported to be abnormally expressed in several cancers (>20) and various other diseases like diabetes-type 2, Crohn' s, pulmonary hypertension, and Alzheimer' s. It regulates important cellular processes such as cell proliferation, differentiation, apoptosis, and migration by targeting important transcription factors, chromatin remodelers, and cell cycle associated genes. Several studies have demonstrated it to be an excellent biomarker for cancer diagnosis and prognosis leading to two patents already in its kitty. In this first review we summarize the current knowledge of the regulation, functions and targets of miR-191 and discuss its potential as a promising disease biomarker and therapeutic target.
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Affiliation(s)
- Neha Nagpal
- RNA-II Lab, Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi New Delhi, India
| | - Ritu Kulshreshtha
- RNA-II Lab, Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi New Delhi, India
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Sausville E, Lorusso P, Carducci M, Carter J, Quinn MF, Malburg L, Azad N, Cosgrove D, Knight R, Barker P, Zabludoff S, Agbo F, Oakes P, Senderowicz A. Phase I dose-escalation study of AZD7762, a checkpoint kinase inhibitor, in combination with gemcitabine in US patients with advanced solid tumors. Cancer Chemother Pharmacol 2014; 73:539-49. [PMID: 24448638 DOI: 10.1007/s00280-014-2380-5] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 01/08/2014] [Indexed: 12/17/2022]
Abstract
PURPOSE AZD7762 is a Chk1 kinase inhibitor which increases sensitivity to DNA-damaging agents, including gemcitabine. We evaluated the safety of AZD7762 monotherapy and with gemcitabine in advanced solid tumor patients. EXPERIMENTAL DESIGN In this Phase I study, patients received intravenous AZD7762 on days 1 and 8 of a 14-day run-in cycle (cycle 0; AZD7762 monotherapy), followed by AZD7762 plus gemcitabine 750-1,000 mg/m(2) on days 1 and 8, every 21 days, in ascending AZD7762 doses (cycle 1; combination therapy). RESULTS Forty-two patients received AZD7762 6 mg (n = 9), 9 mg (n = 3), 14 mg (n = 6), 21 mg (n = 3), 30 mg (n = 7), 32 mg (n = 6), and 40 mg (n = 8), in combination with gemcitabine. Common adverse events (AEs) were fatigue [41 % (17/42) patients], neutropenia/leukopenia [36 % (15/42) patients], anemia/Hb decrease [29 % (12/42) patients] and nausea, pyrexia and alanine aminotransferase/aspartate aminotransferase increase [26 % (11/42) patients each]. Grade ≥3 AEs occurred in 19 and 52 % of patients in cycles 0 and 1, respectively. Cardiac dose-limiting toxicities occurred in two patients (both AZD7762 monotherapy): grade 3 troponin I increase (32 mg) and grade 3 myocardial ischemia with chest pain, electrocardiogram changes, decreased left ventricular ejection fraction, and increased troponin I (40 mg). AZD7762 exposure increased linearly. Gemcitabine did not affect AZD7762 pharmacokinetics. Two non-small-cell lung cancer patients achieved partial tumor responses (AZD7762 6 mg/gemcitabine 750 mg/m(2) and AZD7762 9 mg cohort). CONCLUSIONS The maximum-tolerated dose of AZD7762 in combination with gemcitabine 1,000 mg/m(2) was 30 mg. Although development of AZD7762 is not going forward owing to unpredictable cardiac toxicity, Chk1 remains an important therapeutic target.
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Affiliation(s)
- Edward Sausville
- Marlene and Stewart Greenebaum Cancer Center, University of Maryland, 22 S. Greene Street, Baltimore, MD, 21201, USA,
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The dual roles of geminin during trophoblast proliferation and differentiation. Dev Biol 2014; 387:49-63. [PMID: 24412371 DOI: 10.1016/j.ydbio.2013.12.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 12/11/2013] [Accepted: 12/22/2013] [Indexed: 11/21/2022]
Abstract
Geminin is a protein involved in both DNA replication and cell fate acquisition. Although it is essential for mammalian preimplantation development, its role remains unclear. In one study, ablation of the geminin gene (Gmnn) in mouse preimplantation embryos resulted in apoptosis, suggesting that geminin prevents DNA re-replication, whereas in another study it resulted in differentiation of blastomeres into trophoblast giant cells (TGCs), suggesting that geminin regulates trophoblast specification and differentiation. Other studies concluded that trophoblast differentiation into TGCs is regulated by fibroblast growth factor-4 (FGF4), and that geminin is required to maintain endocycles. Here we show that ablation of Gmnn in trophoblast stem cells (TSCs) proliferating in the presence of FGF4 closely mimics the events triggered by FGF4 deprivation: arrest of cell proliferation, formation of giant cells, excessive DNA replication in the absence of DNA damage and apoptosis, and changes in gene expression that include loss of Chk1 with up-regulation of p57 and p21. Moreover, FGF4 deprivation of TSCs reduces geminin to a basal level that is required for maintaining endocycles in TGCs. Thus, geminin acts both like a component of the FGF4 signal transduction pathway that governs trophoblast proliferation and differentiation, and geminin is required to maintain endocycles.
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Davis SW, Ellsworth BS, Peréz Millan MI, Gergics P, Schade V, Foyouzi N, Brinkmeier ML, Mortensen AH, Camper SA. Pituitary gland development and disease: from stem cell to hormone production. Curr Top Dev Biol 2013; 106:1-47. [PMID: 24290346 DOI: 10.1016/b978-0-12-416021-7.00001-8] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Many aspects of pituitary development have become better understood in the past two decades. The signaling pathways regulating pituitary growth and shape have emerged, and the balancing interactions between the pathways are now appreciated. Markers for multipotent progenitor cells are being identified, and signature transcription factors have been discovered for most hormone-producing cell types. We now realize that pulsatile hormone secretion involves a 3D integration of cellular networks. About a dozen genes are known to cause pituitary hypoplasia when mutated due to their essential roles in pituitary development. Similarly, a few genes are known that predispose to familial endocrine neoplasia, and several genes mutated in sporadic pituitary adenomas are documented. In the next decade, we anticipate gleaning a deeper appreciation of these processes at the molecular level, insight into the development of the hypophyseal portal blood system, and evolution of better therapeutics for congenital and acquired hormone deficiencies and for common craniopharyngiomas and pituitary adenomas.
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Affiliation(s)
- Shannon W Davis
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, USA
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