1
|
Chastain PD, Brylawski BP, Zhou YC, Rao S, Chu H, Ibrahim JG, Kaufmann WK, Cordeiro-Stone M. DNA damage checkpoint responses in the S phase of synchronized diploid human fibroblasts. Photochem Photobiol 2014; 91:109-16. [PMID: 25316620 PMCID: PMC4303954 DOI: 10.1111/php.12361] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 10/08/2014] [Indexed: 01/05/2023]
Abstract
We investigated the hypothesis that the strength of the activation of the intra-S DNA damage checkpoint varies within the S phase. Synchronized diploid human fibroblasts were exposed to either 0 or 2.5 J m−2 UVC in early, mid- and late-S phase. The endpoints measured were the following: (1) radio-resistant DNA synthesis (RDS), (2) induction of Chk1 phosphorylation, (3) initiation of new replicons and (4) length of replication tracks synthesized after irradiation. RDS analysis showed that global DNA synthesis was inhibited by approximately the same extent (30 ± 12%), regardless of when during S phase the fibroblasts were exposed to UVC. Western blot analysis revealed that the UVC-induced phosphorylation of checkpoint kinase 1 (Chk1) on serine 345 was high in early and mid S but 10-fold lower in late S. DNA fiber immunostaining studies indicated that the replication fork displacement rate decreased in irradiated cells at the three time points examined; however, replicon initiation was inhibited strongly in early and mid S, but this response was attenuated in late S. These results suggest that the intra-S checkpoint activated by UVC-induced DNA damage is not as robust toward the end of S phase in its inhibition of the latest firing origins in human fibroblasts.
Collapse
Affiliation(s)
- Paul D Chastain
- College of Osteopathic Medicine, William Carey University, Hattiesburg, MS
| | | | | | | | | | | | | | | |
Collapse
|
2
|
Ando M, Yoshikawa K, Iwase Y, Ishiura S. Usefulness of monitoring γ-H2AX and cell cycle arrest in HepG2 cells for estimating genotoxicity using a high-content analysis system. ACTA ACUST UNITED AC 2014; 19:1246-54. [PMID: 24980598 DOI: 10.1177/1087057114541147] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Formation of the phosphorylated protein γ-H2AX is a well-established marker of DNA strand breakage induced by DNA-damaging compounds. Many of these genotoxic compounds also inhibit cell division, leading to arrest at specific points in the cell cycle. Detection of γ-H2AX in combination with cell cycle arrest may therefore be useful for estimating the genotoxicity of experimental compounds. In this study, we examined γ-H2AX formation and cell cycle arrest using high-content screening (HCS) as a method for determining genotoxicity. HepG2 cells were treated with a panel of compounds and then stained with Hoechst 33342 and anti-γ-H2AX, anti-phospho-histone H3, and anti-tubulin antibodies. In total, 19 genotoxic and 7 nongenotoxic compounds were tested in this study. γ-H2AX production was observed within 1 h posttreatment for the majority of Ames-positive compounds, topoisomerase inhibitors, and DNA polymerase inhibitors. Cell cycle arrest in either the S or G2 phase was detected for all DNA-damaging compounds 24 h posttreatment, whereas tubulin-targeting compounds were shown to induce cell cycle arrest in the mitotic phase. Together, these results show that HCS is a simple, rapid, and effective tool for estimating the genotoxicity of compounds through detection of γ-H2AX production and cell cycle arrest.
Collapse
Affiliation(s)
- Masamitsu Ando
- Safety Research Laboratories, Mitsubishi Tanabe Pharma Corporation, Chiba, Japan Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Keisuke Yoshikawa
- Safety Research Laboratories, Mitsubishi Tanabe Pharma Corporation, Chiba, Japan
| | - Yumiko Iwase
- Safety Research Laboratories, Mitsubishi Tanabe Pharma Corporation, Chiba, Japan
| | - Shoichi Ishiura
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
3
|
Sheppard CL, Lee LCY, Hill EV, Henderson DJP, Anthony DF, Houslay DM, Yalla KC, Cairns LS, Dunlop AJ, Baillie GS, Huston E, Houslay MD. Mitotic activation of the DISC1-inducible cyclic AMP phosphodiesterase-4D9 (PDE4D9), through multi-site phosphorylation, influences cell cycle progression. Cell Signal 2014; 26:1958-74. [PMID: 24815749 DOI: 10.1016/j.cellsig.2014.04.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 04/28/2014] [Accepted: 04/29/2014] [Indexed: 10/25/2022]
Abstract
In Rat-1 cells, the dramatic decrease in the levels of both intracellular cyclic 3'5' adenosine monophosphate (cyclic AMP; cAMP) and in the activity of cAMP-activated protein kinase A (PKA) observed in mitosis was paralleled by a profound increase in cAMP hydrolyzing phosphodiesterase-4 (PDE4) activity. The decrease in PKA activity, which occurs during mitosis, was attributable to PDE4 activation as the PDE4 selective inhibitor, rolipram, but not the phosphodiesterase-3 (PDE3) inhibitor, cilostamide, specifically ablated this cell cycle-dependent effect. PDE4 inhibition caused Rat-1 cells to move from S phase into G2/M more rapidly, to transit through G2/M more quickly and to remain in G1 for a longer period. Inhibition of PDE3 elicited no observable effects on cell cycle dynamics. Selective immunopurification of each of the four PDE4 sub-families identified PDE4D as being selectively activated in mitosis. Subsequent analysis uncovered PDE4D9, an isoform whose expression can be regulated by Disrupted-In-Schizophrenia 1 (DISC1)/activating transcription factor 4 (ATF4) complex, as the sole PDE4 species activated during mitosis in Rat-1 cells. PDE4D9 becomes activated in mitosis through dual phosphorylation at Ser585 and Ser245, involving the combined action of ERK and an unidentified 'switch' kinase that has previously been shown to be activated by H2O2. Additionally, in mitosis, PDE4D9 also becomes phosphorylated at Ser67 and Ser81, through the action of MK2 (MAPKAPK2) and AMP kinase (AMPK), respectively. The multisite phosphorylation of PDE4D9 by all four of these protein kinases leads to decreased mobility (band-shift) of PDE4D9 on SDS-PAGE. PDE4D9 is predominantly concentrated in the perinuclear region of Rat-1 cells but with a fraction distributed asymmetrically at the cell margins. Our investigations demonstrate that the diminished levels of cAMP and PKA activity that characterise mitosis are due to enhanced cAMP degradation by PDE4D9. PDE4D9, was found to locate primarily not only in the perinuclear region of Rat-1 cells but also at the cell margins. We propose that the sequestration of PDE4D9 in a specific complex together with AMPK, ERK, MK2 and the H2O2-activatable 'switch' kinase allows for its selective multi-site phosphorylation, activation and regulation in mitosis.
Collapse
Affiliation(s)
- Catherine L Sheppard
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Louisa C Y Lee
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Elaine V Hill
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - David J P Henderson
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Diana F Anthony
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Daniel M Houslay
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Krishna C Yalla
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Lynne S Cairns
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Allan J Dunlop
- Institute of Neuroscience and Psychology, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - George S Baillie
- Institute of Cardiovascular and Medical Sciences, Wolfson Link and Davidson Buildings, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK
| | - Elaine Huston
- Institute of Pharmaceutical Science, King's College London, 5th Floor, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK
| | - Miles D Houslay
- Institute of Pharmaceutical Science, King's College London, 5th Floor, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
| |
Collapse
|
4
|
Kaufman DG, Cohen SM, Chastain PD. Temporal and functional analysis of DNA replicated in early S phase. ACTA ACUST UNITED AC 2010; 51:257-71. [PMID: 21093474 DOI: 10.1016/j.advenzreg.2010.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 11/10/2010] [Indexed: 12/12/2022]
Abstract
In summary, recently developed technologies have begun to draw back the curtain of mystery that obscures some of the basic mechanisms of DNA replication at multiple levels. Studies using extended DNA and chromatin fiber techniques have proven valuable for identifying the location of origins of replication at specific genomic sites and determining their temporal order of replication, for identifying and quantifying sites of DNA damage and localizing chromatin proteins in relation to sites of DNA replication. The future potential of these methods include further discoveries in functional genomics and contributions to the elucidation of the histone code. Such studies could prove very valuable in studies of the mechanisms of cancer development, aging, and other processes of disordered genomic functioning.
Collapse
Affiliation(s)
- David G Kaufman
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | | | | |
Collapse
|
5
|
Palumbo E, Matricardi L, Tosoni E, Bensimon A, Russo A. Replication dynamics at common fragile site FRA6E. Chromosoma 2010; 119:575-87. [PMID: 20585795 DOI: 10.1007/s00412-010-0279-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 05/21/2010] [Accepted: 05/25/2010] [Indexed: 11/30/2022]
Abstract
The replication dynamics at common fragile site FRA6E has been evaluated by molecular combing and interphase fluorescent in situ hybridisation (FISH) in primary human lymphocytes cultured under normal or aphidicolin-induced stress conditions. FRA6E is one of the most frequently expressed common fragile sites of the human genome. It harbours several genes, PARK2 being regarded as the most relevant one. According to the results obtained from interphase FISH analysis, FRA6E can be considered a mid-late-replicating sequence characterised by heterogeneous replication timing. Molecular combing did not reveal specific replication parameters at the fragile site: fork rates were highly comparable to those detected at an early replicating locus (LMNB2) used as control and in very good agreement with the whole-genome data obtained in parallel. The same indication applied to the density of initiation zones, the inter-origin distances from adjacent ongoing forks, the frequencies of unidirectional forks, fork arrest events and asynchronous forks. Interestingly, PARK2 appeared embedded in an early/late replication transition zone, corresponding to intron 8 (162 kb) and to the fragility core of FRA6E. In cells exposed to aphidicolin, few forks progressing at a rather slow rate were observed, the majority of them being unidirectional, but again a specific response of the fragile site was not observed. In summary, at FRA6E the replication process is not impaired per se, but chromosome breakages occur preferentially at an early/late replication transition zone. Aphidicolin might increase the occurrence of breakage events at FRA6E by prolonging the time interval separating the replication of early and late replication domains. These results may be of general significance to address the problem of fragile site instability.
Collapse
Affiliation(s)
- Elisa Palumbo
- Department of Biology, University of Padova, Via U. Bassi 58/b, 35131, Padova, Italy
| | | | | | | | | |
Collapse
|
6
|
Frum RA, Chastain PD, Qu P, Cohen SM, Kaufman DG. DNA replication in early S phase pauses near newly activated origins. Cell Cycle 2008; 7:1440-8. [PMID: 18418075 DOI: 10.4161/cc.7.10.5879] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
During the S phase of the cell cycle, the entire genome is replicated. There is a high level of orderliness to this process through the temporally and topologically coordinated activation of many replication origins situated along chromosomes. We investigated the program of replication from origins initiating in early S phase by labeling synchronized normal human fibroblasts (NHF1) with nucleotide analogs for various pulse times and measuring labeled tracks in combed DNA fibers. Our analysis showed that replication forks progress 9-35 kilobases from newly initiated origins, followed by a pause in synthesis before replication resumes. Pausing was not observed near origins that initiated in the middle of S phase. No evidence for pausing near origins was found at the beginning of the S phase in glioblastoma T98G cells. Treatment with the S phase checkpoint inhibitor caffeine abrogated pausing in NHF1 cells in early S phase. This suggests that pausing may comprise a novel aspect of the intra-S phase checkpoint pathway or a related new early S checkpoint. Further, it is possible that the loss of this regulatory process in cancer cells such as T98G could be a contributing factor in the genetic instability that typifies cancers.
Collapse
Affiliation(s)
- Rebecca A Frum
- Department of Pathology and Laboratory Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7525, USA
| | | | | | | | | |
Collapse
|
7
|
Kaufman DG, Cordeiro-Stone M, Brylawski BP, Cohen SM, Chastain PD. Early S phase DNA replication: a search for targets of carcinogenesis. ACTA ACUST UNITED AC 2006; 47:127-38. [PMID: 17337290 PMCID: PMC2063577 DOI: 10.1016/j.advenzreg.2006.12.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- David G Kaufman
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599-7525, USA.
| | | | | | | | | |
Collapse
|
8
|
Cohen SM, Furey TS, Doggett NA, Kaufman DG. Genome-wide sequence and functional analysis of early replicating DNA in normal human fibroblasts. BMC Genomics 2006; 7:301. [PMID: 17134498 PMCID: PMC1702361 DOI: 10.1186/1471-2164-7-301] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Accepted: 11/29/2006] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The replication of mammalian genomic DNA during the S phase is a highly coordinated process that occurs in a programmed manner. Recent studies have begun to elucidate the pattern of replication timing on a genomic scale. Using a combination of experimental and computational techniques, we identified a genome-wide set of the earliest replicating sequences. This was accomplished by first creating a cosmid library containing DNA enriched in sequences that replicate early in the S phase of normal human fibroblasts. Clone ends were then sequenced and aligned to the human genome. RESULTS By clustering adjacent or overlapping early replicating clones, we identified 1759 "islands" averaging 100 kb in length, allowing us to perform the most detailed analysis to date of DNA characteristics and genes contained within early replicating DNA. Islands are enriched in open chromatin, transcription related elements, and Alu repetitive elements, with an underrepresentation of LINE elements. In addition, we found a paucity of LTR retroposons, DNA transposon sequences, and an enrichment in all classes of tandem repeats, except for dinucleotides. CONCLUSION An analysis of genes associated with islands revealed that nearly half of all genes in the WNT family, and a number of genes in the base excision repair pathway, including four of ten DNA glycosylases, were associated with island sequences. Also, we found an overrepresentation of members of apoptosis-associated genes in very early replicating sequences from both fibroblast and lymphoblastoid cells. These data suggest that there is a temporal pattern of replication for some functionally related genes.
Collapse
Affiliation(s)
- Stephanie M Cohen
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Terrence S Furey
- Institute for Genome Sciences and Policy, Duke University, Durham, NC, 27708, USA
| | - Norman A Doggett
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - David G Kaufman
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| |
Collapse
|
9
|
Wieder KJ, King KR, Thompson DM, Zia C, Yarmush ML, Jayaraman A. Optimization of Reporter Cells for Expression Profiling in a Microfluidic Device. Biomed Microdevices 2005; 7:213-22. [PMID: 16133809 DOI: 10.1007/s10544-005-3028-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The emergence of green fluorescence protein (GFP) technologies has enabled non-invasive monitoring of cell function and gene expression. GFP-based expression studies are typically performed in traditional single-dish or multi-well formats to monitor a small number of genes or conditions that do not lend well to scaling, high-throughput analysis, or single-cell measurements. We have recently developed a microfluidic device, the Living Cell Array (LCA), for monitoring GFP-based gene expression in a high-throughput manner. Here, we report the optimization of GFP reporter cell characteristics in this microfluidic device for gene expression profiling. A reporter cell line for the transcription factor NF-kappa B was generated and used as the model cell line. Reporter cells were seeded in the LCA and NF-kappa B activated by addition of the cytokine TNF-alpha . Our studies show that the fluorescence kinetics from the reporter cell line in response to both single and repeated TNF-alpha stimulation in the LCA is similar to that observed in standard tissue culture. In addition, our data also indicate that multiple expression waves can be reliably monitored from a small population of reporter cells. Using reporter cell line subcloning and cell cycle synchronization, we demonstrate that the kinetics and magnitude of induced fluorescence in the reporter cell lines can be further improved to maximize the fluorescence readout from reporter cell lines, thereby improving their applicability to live cell expression profiling. Our studies establish some of the important criteria to be considered when using reporter cell lines for dynamic expression profiling in microfluidic devices.
Collapse
Affiliation(s)
- Kenneth J Wieder
- Center for Engineering in Medicine/Department of Surgery, Massachusetts General Hospital, Shriners Hospitals for Children, Harvard Medical School, Boston, MA 02114, USA
| | | | | | | | | | | |
Collapse
|
10
|
Cordeiro-Stone M, Frank A, Bryant M, Oguejiofor I, Hatch SB, McDaniel LD, Kaufmann WK. DNA damage responses protect xeroderma pigmentosum variant from UVC-induced clastogenesis. Carcinogenesis 2002; 23:959-65. [PMID: 12082017 DOI: 10.1093/carcin/23.6.959] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Lack of DNA polymerase eta and the attendant defect in bypass replication of pyrimidine dimers induced in DNA by ultraviolet light (UV) underlie the enhanced mutagenesis and carcinogenesis observed in xeroderma pigmentosum variant (XP-V). We investigated whether diploid XP-V fibroblasts growing in culture are also more susceptible to UV-induced clastogenesis than normal human fibroblasts (NHF). This study utilized diploid fibroblasts immortalized by the ectopic expression of human telomerase. The cell lines displayed checkpoint responses to DNA damage comparable with those measured in the parental strains. Shortly after exposure to low doses of UVC (< or =4 J/m2), XP-V cells accumulated daughter strand gaps in excess of normal controls (>25-fold). Daughter strand gaps generated in UV-irradiated S phase cells are potential precursors of chromatid-type chromosomal aberrations. Nonetheless, chromatid-type chromosomal aberrations were only 1.5 to 2 times more abundant in XP-V than in NHF exposed to the same UVC dose. XP-V cells, however, displayed S phase delays at lower doses of UVC and for longer periods of time than NHF. These results support the hypothesis that aberrant DNA structures activate S phase checkpoint responses that increase the time available for postreplication repair. Alternatively, cells that cannot be properly repaired remain permanently arrested and never reach mitosis. These responses protect human cells from chromosomal aberrations, especially when other pathways, such as accurate lesion bypass, are lost.
Collapse
Affiliation(s)
- Marila Cordeiro-Stone
- Department of Pathology and Laboratory Medicine, University of NC at Chapel Hill, Chapel Hill, NC 27599-7525, USA.
| | | | | | | | | | | | | |
Collapse
|
11
|
Michaelis M, Vogel JU, Cinatl J, Langer K, Kreuter J, Schwabe D, Driever PH, Cinatl J. Cytotoxicity of aphidicolin and its derivatives against neuroblastoma cells in vitro: synergism with doxorubicin and vincristine. Anticancer Drugs 2000; 11:479-85. [PMID: 11001389 DOI: 10.1097/00001813-200007000-00009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Disseminated neuroblastoma diseases are still indicated by a poor outcome despite treatment regimens including radiation therapy and high-dose chemotherapy with stem cell rescue. Therefore, new substances and treatment regimens are of interest. Aphidicolin (APH), a tetracyclic diterpene antibiotic produced by Cephalosporium aphidicola, has a specific toxicity for neuroblastoma cells. Furthermore, it was shown to enhance the effects of X-ray radiation and chemotherapy on malignant cells. To find new substances, 20 APH derivatives were tested for their anti-neuroblastoma efficacy in vitro in UKF-NB-2 cells. Five derivatives had antitumoral activity in neuroblastoma cells. A relationship between the structure and the antitumoral efficacy showed that the hydroxyl groups at C-3 and C-18 are essential for the antitumoral effects. Furthermore, antitumoral effects of APH in combination with doxorubicin and vincristine, both part of commonly used treatment regimens for disseminated neuroblastoma diseases, were tested in the neuroblastoma cell line UKF-NB-2. APH was found to act synergistically with vincristine and synergistically to additive with doxorubicin depending on the molecular ratio of the substances in combination. This may offer the chance to use APH and its derivatives as additional tools in the treatment of neuroblastomas.
Collapse
Affiliation(s)
- M Michaelis
- Institut für Medizinische Virologie, Klinikum der Johann Wolfgang Goethe Universität, Frankfurt am Main, Germany
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Brylawski BP, Cohen SM, Longmire JL, Doggett NA, Cordeiro-Stone M, Kaufman DG. Construction of a cosmid library of DNA replicated early in the S phase of normal human fibroblasts. J Cell Biochem 2000; 78:509-17. [PMID: 10861848 DOI: 10.1002/1097-4644(20000901)78:3<509::aid-jcb15>3.0.co;2-d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We constructed a subgenomic cosmid library of DNA replicated early in the S phase of normal human diploid fibroblasts. Cells were synchronized by release from confluence arrest and incubation in the presence of aphidicolin. Bromodeoxyuridine (BrdUrd) was added to aphidicolin-containing medium to label DNA replicated as cells entered S phase. Nuclear DNA was partially digested with Sau 3AI, and hybrid density DNA was separated in CsCl gradients. The purified early-replicating DNA was cloned into sCos1 cosmid vector. Clones were transferred individually into the wells of 96 microtiter plates (9,216 potential clones). Vigorous bacterial growth was detected in 8,742 of those wells. High-density colony hybridization filters (1, 536 clones/filter) were prepared from a set of replicas of the original plates. Bacteria remaining in the wells of replica plates were combined, mixed with freezing medium, and stored at -80 degrees C. These pooled stocks were analyzed by polymerase chain reaction to determine the presence of specific sequences in the library. Hybridization of high-density filters was used to identify the clones of interest, which were retrieved from the frozen cultures in the 96-well plates. In testing the library for the presence of 14 known early-replicating genes, we found sequences at or near 5 of them: APRT, beta-actin, beta-tubulin, c-myc, and HPRT. This library is a valuable resource for the isolation and analysis of certain DNA sequences replicated at the beginning of S phase, including potential origins of bidirectional replication.
Collapse
Affiliation(s)
- B P Brylawski
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill 27599, USA
| | | | | | | | | | | |
Collapse
|
13
|
Cohen SM, Cobb ER, Cordeiro-Stone M, Kaufman DG. Identification of chromosomal bands replicating early in the S phase of normal human fibroblasts. Exp Cell Res 1998; 245:321-9. [PMID: 9851873 DOI: 10.1006/excr.1998.4258] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Normal human fibroblasts (NHF1) were released from confluence arrest (G0) and replated in medium containing bromodeoxyuridine (BrdU) and aphidicolin. Despite severe reduction in the rate of DNA synthesis by aphidicolin, cells reentering the cell cycle incorporated BrdU at regions of the human genome that replicated very early in S phase. After removal of aphidicolin and BrdU from the tissue culture medium, cells were collected in mitosis. Q-banding with 4', 6-diamidino-2-phenylindole/actinomycin D was used to identify metaphase chromosomes. A monoclonal anti-BrdU antibody and a fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse antibody were used to identify the BrdU-labeled sites. The criterion for scoring DNA replication sites was the detection of FITC fluorescence at homologous regions of both sister chromatids. Early replicating regions mapped within R-bands, but not all R-bands incorporated BrdU. Chromosomal bands 1p36.1, 8q24.1, 12q13, 15q15, 15q22, and 22q13 were labeled in 53% or more of the copies of these chromosomes in the data set, suggesting that these sites replicated very early in S phase. Chromosomal band 15q22 was the most frequently labeled site (64%), which indicates that it contains some of the earliest replicating sequences in normal human fibroblasts.
Collapse
Affiliation(s)
- S M Cohen
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-7525, USA
| | | | | | | |
Collapse
|
14
|
Ma H, Samarabandu J, Devdhar RS, Acharya R, Cheng PC, Meng C, Berezney R. Spatial and temporal dynamics of DNA replication sites in mammalian cells. J Biophys Biochem Cytol 1998; 143:1415-25. [PMID: 9852140 PMCID: PMC2132991 DOI: 10.1083/jcb.143.6.1415] [Citation(s) in RCA: 235] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Fluorescence microscopic analysis of newly replicated DNA has revealed discrete granular sites of replication (RS). The average size and number of replication sites from early to mid S-phase suggest that each RS contains numerous replicons clustered together. We are using fluorescence laser scanning confocal microscopy in conjunction with multidimensional image analysis to gain more precise information about RS and their spatial-temporal dynamics. Using a newly improved imaging segmentation program, we report an average of approximately 1,100 RS after a 5-min pulse labeling of 3T3 mouse fibroblast cells in early S-phase. Pulse-chase-pulse double labeling experiments reveal that RS take approximately 45 min to complete replication. Appropriate calculations suggest that each RS contains an average of 1 mbp of DNA or approximately 6 average-sized replicons. Double pulse-double chase experiments demonstrate that the DNA sequences replicated at individual RS are precisely maintained temporally and spatially as the cell progresses through the cell cycle and into subsequent generations. By labeling replicated DNA at the G1/S borders for two consecutive cell generations, we show that the DNA synthesized at early S-phase is replicated at the same time and sites in the next round of replication.
Collapse
Affiliation(s)
- H Ma
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, New York 14260, USA
| | | | | | | | | | | | | |
Collapse
|
15
|
Martelli AM, Capitani S, Neri LM. Prereplicative increase of nuclear matrix-bound DNA polymerase-alpha and primase activities in HeLa S3 cells following dilution of long-term cultures. J Cell Biochem 1998; 71:11-20. [PMID: 9736450 DOI: 10.1002/(sici)1097-4644(19981001)71:1<11::aid-jcb2>3.0.co;2-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We investigated the association of DNA polymerase and DNA primase activity with the nuclear matrix in HeLa S3 cells diluted with fresh medium after having been cultured without any medium change for 7 days. Flow cytometric analysis demonstrated that just before dilution about 85% of the cells were in the G1 phase of the cycle, whereas 8% were in the S phase. After dilution with fresh medium, 18-22 h were required for the cell population to attain a stable distribution with respect to the cell cycle. At that time, about 38% of the cells were in the S phase. DNA polymerase and DNA primase activity associated with the nuclear matrix prepared from cells just before dilution represented about 10% of nuclear activity. As judged by [3H]-thymidine incorporation and flow cytometric analysis, an increase in the number of S-phase cells was evident at least 6 h after dilution. However, as early as 2 h after dilution into fresh medium, a striking prereplicative increase of the two activities was seen in the nuclear matrix fraction but not in cytosol or isolated nuclei. Both DNA polymerase and primase activities bound to the matrix were about 60% of nuclear activity. Overall, the nuclear matrix was the cell fraction where the highest induction (about 10-fold) of both enzymatic activities was seen at 30 h after dilution, whereas in cytosol and isolated nuclei the increase was about two- and fourfold, respectively. Typical immunofluorescent patterns given by an antibody to 5-bromodeoxyuridine were seen after dilution. These findings, which are at variance with our own previous results obtained with cell cultures synchronized by either a double thymidine block or aphidicolin exposure, strengthen the contention that DNA replication is associated with an underlying nuclear structure and demonstrate the artifacts that may be generated by procedures commonly used to synchronize cell cultures.
Collapse
Affiliation(s)
- A M Martelli
- Dipartimento di Morfologia Umana Normale, Università di Trieste, Italy.
| | | | | |
Collapse
|
16
|
Tanaka T, Murakami K, Kanda A, Patra D, Yamamoto S, Satoh N, Kim SW, Ishida T, In Y, Iwata C. Total synthesis of (±)-stemodinone. Tetrahedron Lett 1997. [DOI: 10.1016/s0040-4039(97)00173-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
17
|
Erba E, Sen S. Synchronization of cancer cell lines with methotrexate in vitro. ACTA ACUST UNITED AC 1996. [DOI: 10.1007/bf00122166] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
18
|
Igawa M, Tanabe T, Chodak GW, Rukstalis DB. N-(4-hydroxyphenyl) retinamide induces cell cycle specific growth inhibition in PC3 cells. Prostate 1994; 24:299-305. [PMID: 8208624 DOI: 10.1002/pros.2990240605] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The synthetic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR) has been demonstrated to inhibit the development of primary and metastatic neoplasms in several animal models. In order to investigate the effect of 4-HPR on human prostate adenocarcinoma, we designed a series of in vitro experiments with the PC3 cell line to evaluate effects on proliferation, cell cycle kinetics, and c-myc mRNA expression. 4-HPR demonstrated cytotoxicity only at the supraphysiologic concentration of 10.0 microM. However, asynchronously growing cells exposed to 1 microM 4-HPR demonstrated a 51% reduction in proliferation rate, associated with an accumulation of cells in the G0/G1 phase of the cell cycle. PC3 cells synchronized with serum deprivation or aphidicolin exhibited significant decreases in DNA synthesis when treated with 1 microM 4-HPR. Additionally, these cells were found to accumulate in G0/G1 and S phase. Northern blots indicated a significant decrease in c-myc mRNA expression in asynchronously growing cells with continuous administration of 1 microM 4-HPR for 6 days. These data suggest that 4-HPR can inhibit growth of PC3 cells as a consequence of a block in cell cycle transition from G1 to S phase at a concentration of 1 microM, and that this inhibition is associated with a suppression of c-myc gene expression.
Collapse
Affiliation(s)
- M Igawa
- Department of Surgery, University of Chicago, Illinois
| | | | | | | |
Collapse
|
19
|
Sorscher DH, Barrett JC, Cordeiro-Stone M. Timing of replication of differentially transcribed genes in Syrian hamster embryo fibroblasts. Mol Carcinog 1993; 8:28-33. [PMID: 8352888 DOI: 10.1002/mc.2940080108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Syrian hamster embryo cell lines have been used as models of neoplastic progression in vitro. Changes in phenotype and biological properties have been observed in these cell lines in association with modulation of gene transcription. We explored this natural evolution of cells in culture to investigate the reported relationship between transcriptional activity and replication in early S phase. In this study we used two nontumorigenic cell lines that had either retained (supB+) or lost (supB-) the ability to suppress tumorigenicity of malignantly transformed hamster fibroblasts (BP6T). In association with the loss of suppressor gene function, supB- cells have downregulated the expression of the H19 and tropomyosin-I (TM-I) genes, which are actively transcribed in supB+ cells. Synchronous populations of supB+ and supB- cells were pulse-labeled with [3H]thymidine and bromodeoxyuridine at 1-h intervals during S phase; the replicating DNA was isolated by centrifugation in cesium chloride gradients and hybridized to 32P-labeled gene probes. No correlation was found between the timing of gene replication and the status of expression of these two genes. TM-I replicated during the first hour and H19 replicated between the second and third hours of the S phase in the expressing and nonexpressing cell lines. Immunoglobulin gene sequences, known to be late-replicating in fibroblasts, replicated at the end of the S phase. These results suggest that downregulation of transcription is not always accompanied by a concomitant change in time of gene replication from early to late S phase.
Collapse
Affiliation(s)
- D H Sorscher
- Department of Pathology, University of North Carolina Medical School, Chapel Hill
| | | | | |
Collapse
|
20
|
Characterization of the S-phase-specific transcription regulatory elements in a DNA replication-independent testis-specific H2B (TH2B) histone gene. Mol Cell Biol 1990. [PMID: 2300056 DOI: 10.1128/mcb.10.2.585] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The testis-specific H2B histone (TH2B) gene is expressed in pachytene spermatocytes of meiotic prophase I during rat spermatogenesis. The TH2B RNA and histones are not synthesized in any other tissues, and the synthesis is independent of DNA replication. However, the cloned TH2B gene has two DNA sequence elements which stimulate transcription of the cloned gene in an S-phase-dependent manner when introduced into somatic cells. The factors interacting with the two elements, CCAAT at -127 base pairs and octamer ATTTGCAT at -93 base pairs, interact with each other to bring about a maximum stimulation of S-phase-dependent transcription. The level of CCAAT and octamer-binding proteins is unchanged during the cell cycle, and the S-phase-dependent transcription of TH2B and endogenous mouse H2B genes does not require synthesis of new proteins during the S phase. Cell cycle-specific posttranslational modification of regulatory proteins may be responsible for the S-phase-dependent transcription of H2B histone genes. The biological significance of the presence of S-phase-specific transcription regulatory elements in the DNA replication-independent and tissue-specific TH2B gene is not known.
Collapse
|
21
|
Hwang IW, Lim K, Chae CB. Characterization of the S-phase-specific transcription regulatory elements in a DNA replication-independent testis-specific H2B (TH2B) histone gene. Mol Cell Biol 1990; 10:585-92. [PMID: 2300056 PMCID: PMC360845 DOI: 10.1128/mcb.10.2.585-592.1990] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The testis-specific H2B histone (TH2B) gene is expressed in pachytene spermatocytes of meiotic prophase I during rat spermatogenesis. The TH2B RNA and histones are not synthesized in any other tissues, and the synthesis is independent of DNA replication. However, the cloned TH2B gene has two DNA sequence elements which stimulate transcription of the cloned gene in an S-phase-dependent manner when introduced into somatic cells. The factors interacting with the two elements, CCAAT at -127 base pairs and octamer ATTTGCAT at -93 base pairs, interact with each other to bring about a maximum stimulation of S-phase-dependent transcription. The level of CCAAT and octamer-binding proteins is unchanged during the cell cycle, and the S-phase-dependent transcription of TH2B and endogenous mouse H2B genes does not require synthesis of new proteins during the S phase. Cell cycle-specific posttranslational modification of regulatory proteins may be responsible for the S-phase-dependent transcription of H2B histone genes. The biological significance of the presence of S-phase-specific transcription regulatory elements in the DNA replication-independent and tissue-specific TH2B gene is not known.
Collapse
Affiliation(s)
- I W Hwang
- Department of Biochemistry, University of North Carolina, Chapel Hill 27599-7260
| | | | | |
Collapse
|
22
|
Sen S, Erba E, D'Incalci M. Synchronisation of cancer cell lines of human origin using methotrexate. CYTOMETRY 1990; 11:595-602. [PMID: 2379450 DOI: 10.1002/cyto.990110506] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
U937 human histiocytic lymphoma cell line and SW626 ovarian carcinoma line of human origin were synchronised using very low, nontoxic concentrations (0.04-0.08 microM for 16-24 h) of methotrexate (MTX) under standard culture conditions. Satisfactory synchrony was achieved to study S phase events. Various kinetic behaviours and biological properties of the synchronised cells are considered for characterisation of the system. MTX-synchronisation was compared with that induced by aphidicolin (APC) alone and by serum deprivation and APC. In some cancer cell lines MTX appears to be the best choice for obtaining highly synchronised cell populations without cytotoxicity or physiological perturbations.
Collapse
Affiliation(s)
- S Sen
- Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy
| | | | | |
Collapse
|
23
|
S-phase-specific transcription regulatory elements are present in a replication-independent testis-specific H2B histone gene. Mol Cell Biol 1989. [PMID: 2725487 DOI: 10.1128/mcb.9.3.1005] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The testis-specific H2B histone (TH2B) gene is expressed in pachytene spermatocytes during meiotic prophase I in the absence of any significant DNA synthesis. Unlike somatic histones, synthesis of testis-specific histones is not affected by inhibitors of DNA synthesis. A genomic rat TH2B gene was cloned by using a DNA fragment derived from TH2B cDNA as a probe. Expression of the cloned TH2B was investigated by gene transfer experiments. From these studies, we found that the 5' upstream region of the cloned TH2B gene contained S-phase-specific transcription elements which regulated expression of a reporter gene in an S-phase-specific manner. The S-phase-regulatory element was found to be located in two regions containing CCAAT elements between -153 and -110 base pairs (bp) and an octamer element (ATTTGCAT) between -109 and -84 bp. The two regions were required for a maximal stimulation of transcription of the cloned TH2B gene in S phase. On the other hand, only the octamer element was reported be important for the S-phase-specific transcription of human H2B gene. Since the synthesis of the TH2B histone is independent of DNA synthesis and specific for pachytene spermatocytes in vivo, the presence of the S-phase-specific transcription regulatory elements in the TH2B gene is surprising.
Collapse
|
24
|
Hwang I, Chae CB. S-phase-specific transcription regulatory elements are present in a replication-independent testis-specific H2B histone gene. Mol Cell Biol 1989; 9:1005-13. [PMID: 2725487 PMCID: PMC362690 DOI: 10.1128/mcb.9.3.1005-1013.1989] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The testis-specific H2B histone (TH2B) gene is expressed in pachytene spermatocytes during meiotic prophase I in the absence of any significant DNA synthesis. Unlike somatic histones, synthesis of testis-specific histones is not affected by inhibitors of DNA synthesis. A genomic rat TH2B gene was cloned by using a DNA fragment derived from TH2B cDNA as a probe. Expression of the cloned TH2B was investigated by gene transfer experiments. From these studies, we found that the 5' upstream region of the cloned TH2B gene contained S-phase-specific transcription elements which regulated expression of a reporter gene in an S-phase-specific manner. The S-phase-regulatory element was found to be located in two regions containing CCAAT elements between -153 and -110 base pairs (bp) and an octamer element (ATTTGCAT) between -109 and -84 bp. The two regions were required for a maximal stimulation of transcription of the cloned TH2B gene in S phase. On the other hand, only the octamer element was reported be important for the S-phase-specific transcription of human H2B gene. Since the synthesis of the TH2B histone is independent of DNA synthesis and specific for pachytene spermatocytes in vivo, the presence of the S-phase-specific transcription regulatory elements in the TH2B gene is surprising.
Collapse
Affiliation(s)
- I Hwang
- Department of Biochemistry, University of North Carolina, Chapel Hill 27599-7260
| | | |
Collapse
|
25
|
Lönn U, Lönn S, Nylen U, Winblad G. Altered formation of DNA replication intermediates in cells growing in different culture conditions. J Cell Physiol 1989; 138:45-9. [PMID: 2910886 DOI: 10.1002/jcp.1041380108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In human melanoma cells one can detect two discrete DNA replication intermediates, 10-kb DNA intermediates and Okakzaki fragments. Both intermediates are seen when cells are rapidly growing in medium supplemented with fetal calf serum. When the medium is supplemented with newborn calf serum, one can detect Okakzaki fragments but not 10-kb DNA intermediates. In contrast we do not detect changes in the replicon sizes in the two media.
Collapse
Affiliation(s)
- U Lönn
- Radiumhemmet, Karolinska Hospital, Stockholm, Sweden
| | | | | | | |
Collapse
|
26
|
Nuclear DNA synthesis in vitro is mediated via stable replication forks assembled in a temporally specific fashion in vivo. Mol Cell Biol 1988. [PMID: 3386630 DOI: 10.1128/mcb.8.5.1923] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A cell-free nuclear replication system that is S-phase specific, that requires the activity of DNA polymerase alpha, and that is stimulated three- to eightfold by cytoplasmic factors from S-phase cells was used to examine the temporal specificity of chromosomal DNA synthesis in vitro. Temporal specificity of DNA synthesis in isolated nuclei was assessed directly by examining the replication of restriction fragments derived from the amplified 200-kilobase dihydrofolate reductase domain of methotrexate-resistant CHOC 400 cells as a function of the cell cycle. In nuclei prepared from cells collected at the G1/S boundary of the cell cycle, synthesis of amplified sequences commenced within the immediate dihydrofolate reductase origin region and elongation continued for 60 to 80 min. The order of synthesis of amplified restriction fragments in nuclei from early S-phase cells in vitro appeared to be indistinguishable from that in vivo. Nuclei prepared from CHOC 400 cells poised at later times in the S phase synthesized characteristic subsets of other amplified fragments. The specificity of fragment labeling patterns was stable to short-term storage at 4 degrees C. The occurrence of stimulatory factors in cytosol extracts was cell cycle dependent in that minimal stimulation was observed with early G1-phase extracts, whereas maximal stimulation was observed with cytosol extracts from S-phase cells. Chromosomal synthesis was not observed in nuclei from G1 cells, nor did cytosol extracts from S-phase cells induce chromosomal replication in G1 nuclei. In contrast to chromosomal DNA synthesis, mitochondrial DNA replication in vitro was not stimulated by cytoplasmic factors and occurred at equivalent rates throughout the G1 and S phases. These studies show that chromosomal DNA replication in isolated nuclei is mediated by stable replication forks that are assembled in a temporally specific fashion in vivo and indicate that the synthetic mechanisms observed in vitro accurately reflect those operative in vivo.
Collapse
|
27
|
Heintz NH, Stillman BW. Nuclear DNA synthesis in vitro is mediated via stable replication forks assembled in a temporally specific fashion in vivo. Mol Cell Biol 1988; 8:1923-31. [PMID: 3386630 PMCID: PMC363370 DOI: 10.1128/mcb.8.5.1923-1931.1988] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
A cell-free nuclear replication system that is S-phase specific, that requires the activity of DNA polymerase alpha, and that is stimulated three- to eightfold by cytoplasmic factors from S-phase cells was used to examine the temporal specificity of chromosomal DNA synthesis in vitro. Temporal specificity of DNA synthesis in isolated nuclei was assessed directly by examining the replication of restriction fragments derived from the amplified 200-kilobase dihydrofolate reductase domain of methotrexate-resistant CHOC 400 cells as a function of the cell cycle. In nuclei prepared from cells collected at the G1/S boundary of the cell cycle, synthesis of amplified sequences commenced within the immediate dihydrofolate reductase origin region and elongation continued for 60 to 80 min. The order of synthesis of amplified restriction fragments in nuclei from early S-phase cells in vitro appeared to be indistinguishable from that in vivo. Nuclei prepared from CHOC 400 cells poised at later times in the S phase synthesized characteristic subsets of other amplified fragments. The specificity of fragment labeling patterns was stable to short-term storage at 4 degrees C. The occurrence of stimulatory factors in cytosol extracts was cell cycle dependent in that minimal stimulation was observed with early G1-phase extracts, whereas maximal stimulation was observed with cytosol extracts from S-phase cells. Chromosomal synthesis was not observed in nuclei from G1 cells, nor did cytosol extracts from S-phase cells induce chromosomal replication in G1 nuclei. In contrast to chromosomal DNA synthesis, mitochondrial DNA replication in vitro was not stimulated by cytoplasmic factors and occurred at equivalent rates throughout the G1 and S phases. These studies show that chromosomal DNA replication in isolated nuclei is mediated by stable replication forks that are assembled in a temporally specific fashion in vivo and indicate that the synthetic mechanisms observed in vitro accurately reflect those operative in vivo.
Collapse
Affiliation(s)
- N H Heintz
- Department of Pathology, University of Vermont College of Medicine, Burlington 05405
| | | |
Collapse
|
28
|
Paules RS, Cordeiro-Stone M, Mass MJ, Poirier MC, Yuspa SH, Kaufman DG. Benzo[alpha]pyrene diol epoxide I binds to DNA at replication forks. Proc Natl Acad Sci U S A 1988; 85:2176-80. [PMID: 3127827 PMCID: PMC279952 DOI: 10.1073/pnas.85.7.2176] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The distribution of lesions in DNA caused by (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [alpha]pyrene (B[alpha]P diol epoxide-I) was studied in synchronized C3H/10T1/2 cells treated in S phase. Sites of carcinogen modification of DNA were identified by polyclonal rabbit antibodies elicited against DNA modified with B[alpha]P diol epoxide-I in vitro. This antigenic DNA contained trans-(7R)-N2-[10-(7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10-tetrahydrobenzo[alpha]pyrene)-yl]- deoxyguanosine; other adducts were not detected by liquid chromatography. In this study, DNA replication forks with antibodies bound to B[alpha]P diol epoxide-I adducts were detected by electron microscopy. The frequency of replication forks containing carcinogen adducts associated with the fork junction was found to be 8-fold higher than expected for an average distribution. The proportion of replication forks that were apparently blocked at the site of the DNA damage increased when replication was allowed to occur after carcinogen exposure. These results support the conclusions that the fork junction is particularly vulnerable to adduction by B[alpha]P diol epoxide-I and that B[alpha]P diol epoxide-I adducts block the displacement of replication forks during DNA synthesis in intact cells.
Collapse
Affiliation(s)
- R S Paules
- Department of Pathology, University of North Carolina, Chapel Hill 27599
| | | | | | | | | | | |
Collapse
|
29
|
Abstract
Ehrlich ascites cells, in which replication units at the beginning of the S phase started and grew synchronously, were obtained by the following protocol: (1) selection of G1 cells by zonal centrifugation, (2) hypoxia for 12 h, (3) reaeration, (4) addition of cycloheximide (30 microM) within the first minute after reoxygenation. Studies on the effectiveness of the different steps revealed: (i) G1 cells reoxygenated after 12 h of hypoxia traverse two succeeding cell cycles highly synchronously. This was shown by monitoring the thymidine incorporation rate, the thymidine pulse-labeling index, and the mitotic index. (ii) Cycloheximide, like hypoxia, suppresses replicon initiation in Ehrlich ascites cells without interfering with DNA chain growth and DNA maturation. The reversibility of the suppression is less complete than in the case of hypoxia. This was shown by DNA fiber autoradiography and by analyzing the length distribution of pulse- or pulse/pulse-chase-labeled daughter DNA in alkaline sucrose gradients. The alkaline sedimentation patterns of daughter-strand DNA, pulse labeled immediately after the cycloheximide addition at the end of the elaborated protocol and 1 and 2 h later, indicated synchronous initiation and growth of a homogeneous population of DNA molecules to replicon-sized lengths.
Collapse
Affiliation(s)
- V Gekeler
- Physiologisch-Chemisches Institut der Universität Tübingen, Federal Republic of Germany
| | | |
Collapse
|
30
|
Radford IR, Broadhurst S. Aphidicolin synchronization of mouse L cells perturbs the relationship between cell killing and DNA double-strand breakage after X-irradiation. INTERNATIONAL JOURNAL OF RADIATION BIOLOGY AND RELATED STUDIES IN PHYSICS, CHEMISTRY, AND MEDICINE 1988; 53:205-15. [PMID: 3126159 DOI: 10.1080/09553008814550571] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mouse L cells were synchronized in early S-phase by two 12 h incubations in medium containing aphidicolin (2 micrograms/ml), separated by 8 h in drug-free medium. The relationship between X-ray-induced cell killing and DNA double-strand breakage was then examined for cells that had entered S-phase, G2-phase, mitosis, and G1-phase following release from aphidicolin and was compared to the response of asynchronous cultures. Aphidicolin-synchronized cells showed cycle phase-dependent changes in their dose-responses for both killing and DNA dsb. However, on the basis of the level of DNA dsb per unit length of DNA required to produce a lethal lesion, aphidicolin-synchronized cells were more sensitive to X-rays than were asynchronous cultures. This sensitivity peaked 2 h after release from aphidicolin treatment and then progressively declined towards the asynchronous culture value. It is argued that these results are due to deregulation of the temporal order of DNA replication following aphidicolin treatment, and can be incorporated into the critical DNA target size model (Radford, Hodgson, and Matthews, in preparation) by postulating that the targets for radiation action in mammalian cells are DNA-associated with potentially transcriptionally active proto-oncogenes or constitutive fragile sites.
Collapse
Affiliation(s)
- I R Radford
- Peter MacCallum Research Laboratories, Peter MacCallum Cancer Institute, Melbourne, Victoria, Australia
| | | |
Collapse
|
31
|
Doggett NA, Cordeiro-Stone M, Chae CB, Kaufman DG. Timing of proto-oncogene replication: a possible determinant of early S phase sensitivity of C3H 10T1/2 cells to transformation by chemical carcinogens. Mol Carcinog 1988; 1:41-9. [PMID: 3255390 DOI: 10.1002/mc.2940010110] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The temporal order of replication of several genes was studied in 10T1/2 cells synchronized by release from confluence-induced arrest of proliferation followed by treatment with 2 micrograms/mL aphidicolin for 24 h. DNA subjected to bromodeoxyuridine substitution for 1- or 2-h intervals spanning the S phase was separated from the remaining DNA in cesium chloride gradients, filtered onto nitrocellulose in a slot-blot apparatus, and hybridized with various 32P-labeled probes. Ha-ras was among the first genes replicated at the onset of the S phase. The myc proto-oncogene replicated later but within the first hour of the S phase. The replication of Ki-ras, raf, and mos was detected between hour 1 and 2 of the S phase. The dihydrofolate reductase gene replicated early (0-2 h) and the myb proto-oncogene replicated in mid-S phase (2-4 h). An immunoglobulin VH sequence and the beta-globin gene replicated late in 10T1/2 cells, 4-6 h after removal of aphidicolin. Replicating DNA is preferentially adducted by chemical carcinogens, and replication of damaged proto-oncogenes before they are repaired may activate their transforming potential. Therefore, the observed replication of proto-oncogenes during the early S phase may underlie the enhanced sensitivity of 10T1/2 cells to chemically induced transformation at this point in the cell cycle.
Collapse
Affiliation(s)
- N A Doggett
- Department of Pathology, Lineberger Cancer Research Center, Chapel Hill, North Carolina 27599
| | | | | | | |
Collapse
|
32
|
Cell cycle variations of dinucleoside polyphosphates in synchronized cultures of mammalian cells. Mol Cell Biol 1987. [PMID: 3475567 DOI: 10.1128/mcb.7.7.2444] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Zajdela hepatoma culture cells (ZHC) and mouse embryo fibroblasts (Swiss 3T3) were synchronized in G1 or S phase by serum deprivation and aphidicolin treatment, respectively, to study the variations in adenylyl nucleotide (Ap4X) pool size during the progress of the cell cycle. Only minor variations, which never exceeded a factor of 2, were observed when the Ap4X concentrations were expressed on a cellular basis. The variations were found to be strictly parallel to the ATP variations. Upon release from an aphidicolin block, the minor variations of Ap4X followed DNA synthesis and preceded cytokinesis. When the nucleotide content was compared with the amount of proteins, the faint specific cell cycle changes were almost completely damped when the cells were synchronized by serum deprivation, but remained practically unchanged in the case of aphidicolin synchronization. These results suggest that the observed variations could reflect the accumulation of some nucleotides before cell division. It is not clear yet whether the variation in Ap4X concentration is significant by itself or is simply a phenomenon resulting from changes in the ATP pool.
Collapse
|
33
|
Orfanoudakis G, Baltzinger M, Meyer D, Befort N, Ebel JP, Befort JJ, Remy P. Cell cycle variations of dinucleoside polyphosphates in synchronized cultures of mammalian cells. Mol Cell Biol 1987; 7:2444-50. [PMID: 3475567 PMCID: PMC365376 DOI: 10.1128/mcb.7.7.2444-2450.1987] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Zajdela hepatoma culture cells (ZHC) and mouse embryo fibroblasts (Swiss 3T3) were synchronized in G1 or S phase by serum deprivation and aphidicolin treatment, respectively, to study the variations in adenylyl nucleotide (Ap4X) pool size during the progress of the cell cycle. Only minor variations, which never exceeded a factor of 2, were observed when the Ap4X concentrations were expressed on a cellular basis. The variations were found to be strictly parallel to the ATP variations. Upon release from an aphidicolin block, the minor variations of Ap4X followed DNA synthesis and preceded cytokinesis. When the nucleotide content was compared with the amount of proteins, the faint specific cell cycle changes were almost completely damped when the cells were synchronized by serum deprivation, but remained practically unchanged in the case of aphidicolin synchronization. These results suggest that the observed variations could reflect the accumulation of some nucleotides before cell division. It is not clear yet whether the variation in Ap4X concentration is significant by itself or is simply a phenomenon resulting from changes in the ATP pool.
Collapse
|
34
|
Lönn U, Lönn S. Conversion of post-elongation stage DNA to mature DNA occurs even if movement of the replication fork has stopped. Chromosoma 1987; 95:171-4. [PMID: 3111800 DOI: 10.1007/bf00330347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
During DNA synthesis there is a distinct stage immediately after the joining of large DNA replication intermediates (post-elongation stage). The conversion of this DNA to mature DNA was analysed in cells treated with aphidicolin to stop the movement of the replication fork. In such cells mature DNA is formed. In contrast, UV-A, which induces a wide spectrum of DNA lesions, inhibits the conversion to mature DNA. The data indicate that the maturation of the post-elongation stage can be uncoupled from the movement of the replication fork.
Collapse
|