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Tan J, Bai J, Yan Z. An Aligned Patterned Biomimetic Elastic Membrane Has a Potential as Vascular Tissue Engineering Material. Front Bioeng Biotechnol 2020; 8:704. [PMID: 32695769 PMCID: PMC7338373 DOI: 10.3389/fbioe.2020.00704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 06/04/2020] [Indexed: 11/24/2022] Open
Abstract
Cardiovascular disease is the leading cause of death worldwide, with an annual mortality incidence predicted to rise to 23.3 million worldwide by 2030. Synthetic vascular grafts as an alternative to autologous vessels have shown satisfactory long-term results for replacement of large- and medium-diameter arteries, but have poor patency rates when applied to small-diameter vessels. Nanoparticles with low toxicity, contrasting agent properties, tailorable characteristics, targeted/stimuli- response delivery potential, and precise control over behavior (via external stimuli such as magnetic fields) have made possible their use for improving engineered tissues. Poly (styrene-block-butadiene-block-styrene) (SBS) is a kind of widely used thermoplastic elastomer with good mechanical properties and biocompatibility. Here, we synthesized anthracene-grafted SBS (SBS-An) by the method for the fabrication of a biomimetic elastic membrane with a switchable Janus structure, and formed the patterns on the surface of SBS-An under ultraviolet (UV) light irradiation. By irradiating the SBS-An film at different times (0, 10, 20, 30, 60, and 120 s), we obtained six well-ordered surface-patterned biomimetic elastic film with SBS-An at different heights in the thickness direction and the same distances of intervals (named sample-0, 10, 20, 30, 60, and 120 s). The structural effects of the SBS-An films on the adhesion and proliferation of human umbilical vein endothelial cells (HUVECs) were studied, and the possible mechanism was explored. When the HUVECs were cultured on the SBS-An films at different heights in the thickness direction, the sample-30 s with approximately 4 μm height significantly promoted adhesion of the HUVECs at the early stage and proliferation during the culture period compared with the samples of the lower (0, 10, and 20 s) and higher (60 and 120 s) heights. Consistent with this, the sample 30 s showed a higher stimulatory effect on the proliferation- and angiogenesis-related genes. These results suggest that SBS-An with appropriate height could efficiently control bioactivities of the biomimetic elastic membrane and might have great potential in vascular tissue engineering application.
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Affiliation(s)
- Juanjuan Tan
- School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composite Materials and Shanghai Key Lab of Electrical Insulation and Thermal Ageing, Shanghai Jiao Tong University, Shanghai, China
- Joint Research Center for Precision Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital South Campus, Shanghai, China
| | - Jing Bai
- School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composite Materials and Shanghai Key Lab of Electrical Insulation and Thermal Ageing, Shanghai Jiao Tong University, Shanghai, China
| | - Zhiqiang Yan
- Central Laboratory, Southern Medical University affiliated Fengxian Hospital, Shanghai, China
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Lan Y, Lou J, Hu J, Yu Z, Lyu W, Zhang B. Downregulation of SNRPG induces cell cycle arrest and sensitizes human glioblastoma cells to temozolomide by targeting Myc through a p53-dependent signaling pathway. Cancer Biol Med 2020; 17:112-131. [PMID: 32296580 PMCID: PMC7142844 DOI: 10.20892/j.issn.2095-3941.2019.0164] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 08/29/2019] [Indexed: 12/17/2022] Open
Abstract
Objective: Temozolomide (TMZ) is commonly used for glioblastoma multiforme (GBM) chemotherapy. However, drug resistance limits its therapeutic effect in GBM treatment. RNA-binding proteins (RBPs) have vital roles in posttranscriptional events. While disturbance of RBP-RNA network activity is potentially associated with cancer development, the precise mechanisms are not fully known. The SNRPG gene, encoding small nuclear ribonucleoprotein polypeptide G, was recently found to be related to cancer incidence, but its exact function has yet to be elucidated. Methods:SNRPG knockdown was achieved via short hairpin RNAs. Gene expression profiling and Western blot analyses were used to identify potential glioma cell growth signaling pathways affected by SNRPG. Xenograft tumors were examined to determine the carcinogenic effects of SNRPG on glioma tissues. Results: The SNRPG-mediated inhibitory effect on glioma cells might be due to the targeted prevention of Myc and p53. In addition, the effects of SNRPG loss on p53 levels and cell cycle progression were found to be Myc-dependent. Furthermore, SNRPG was increased in TMZ-resistant GBM cells, and downregulation of SNRPG potentially sensitized resistant cells to TMZ, suggesting that SNRPG deficiency decreases the chemoresistance of GBM cells to TMZ via the p53 signaling pathway. Our data confirmed that SNRPG suppression sensitizes GBM cells to TMZ by targeting Myc via the p53 signaling cascade. Conclusions: These results indicated that SNRPG is a probable molecular target of GBM and suggested that suppressing SNRPG in resistant GBM cells might be a substantially beneficial method for overcoming essential drug resistance.
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Affiliation(s)
- Yulong Lan
- Department of Neurosurgery, Shenzhen People’s Hospital, Second Clinical Medical College of Jinan University, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen 518020, China
- Department of Neurosurgery, The Second Affiliated Hospital of Dalian Medical University, Dalian 116023, China
| | - Jiacheng Lou
- Department of Neurosurgery, The Second Affiliated Hospital of Dalian Medical University, Dalian 116023, China
| | - Jiliang Hu
- Department of Neurosurgery, Shenzhen People’s Hospital, Second Clinical Medical College of Jinan University, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen 518020, China
| | - Zhikuan Yu
- Department of Neurosurgery, Shenzhen People’s Hospital, Second Clinical Medical College of Jinan University, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen 518020, China
| | - Wen Lyu
- Department of Neurosurgery, Shenzhen People’s Hospital, Second Clinical Medical College of Jinan University, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen 518020, China
| | - Bo Zhang
- Department of Neurosurgery, Shenzhen People’s Hospital, Second Clinical Medical College of Jinan University, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen 518020, China
- Department of Neurosurgery, The Second Affiliated Hospital of Dalian Medical University, Dalian 116023, China
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Physalin B induces cell cycle arrest and triggers apoptosis in breast cancer cells through modulating p53-dependent apoptotic pathway. Biomed Pharmacother 2018; 101:334-341. [DOI: 10.1016/j.biopha.2018.02.094] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 02/05/2018] [Accepted: 02/20/2018] [Indexed: 12/17/2022] Open
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Kelly T. Historical Perspective of Eukaryotic DNA Replication. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:1-41. [PMID: 29357051 DOI: 10.1007/978-981-10-6955-0_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The replication of the genome of a eukaryotic cell is a complex process requiring the ordered assembly of multiprotein replisomes at many chromosomal sites. The process is strictly controlled during the cell cycle to ensure the complete and faithful transmission of genetic information to progeny cells. Our current understanding of the mechanisms of eukaryotic DNA replication has evolved over a period of more than 30 years through the efforts of many investigators. The aim of this perspective is to provide a brief history of the major advances during this period.
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Affiliation(s)
- Thomas Kelly
- Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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Feng SX, Guan Q, Chen T, Du C. In vitro activities of 3-hydroxy-1,5,6-trimethoxy-2-methyl-9,10-anthraquinone against non-small cell lung carcinoma. Arch Pharm Res 2012; 35:1251-8. [DOI: 10.1007/s12272-012-0716-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 02/01/2012] [Accepted: 02/02/2012] [Indexed: 11/24/2022]
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Chen XZ, Cao ZY, Chen TS, Zhang YQ, Liu ZZ, Su YT, Liao LM, Du J. Water extract of Hedyotis Diffusa Willd suppresses proliferation of human HepG2 cells and potentiates the anticancer efficacy of low-dose 5-fluorouracil by inhibiting the CDK2-E2F1 pathway. Oncol Rep 2012; 28:742-8. [PMID: 22641337 DOI: 10.3892/or.2012.1834] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 05/04/2012] [Indexed: 11/06/2022] Open
Abstract
Hedyotis Diffusa Willd (HDW), a Chinese herbal medicine, has been widely used as an adjuvant therapy against various cancers, including hepatocellular carcinoma (HCC). However, the underlying anticancer mechanisms are yet to be elucidated. In the present study, the anticancer effects of HDW were evaluated and the efficacy and safety of HDW combined with low-dose 5-fluorouracil (5-FU) were investigated. HepG2 cells were cultured in vitro and nude mouse xenografts were established in vivo. The proliferation of HepG2 cells was measured using the MTT method and flow cytometry. The mRNA and protein expression levels of cyclin-dependent kinase 2 (CDK2), cyclin E and E2F1 were examined using relative quantitative real-time PCR and western blot analysis, respectively. The results showed that water extract of HDW remarkably inhibited HepG2 cell proliferation in a dose-dependent manner via arrest of HepG2 cells at the G0/G1 phase and induction of S phase delay. This suppression was accompanied by a great decrease of E2F1 and CDK2 mRNA expression. In addition, HDW remarkably potentiated the anticancer effect of low-dose 5-FU in the absence of overt toxicity by downregulating the mRNA and protein levels of CDK2, cyclin E and E2F1. Our findings support the use of HDW as adjuvant therapy of chemotherapy and suggest that HDW may potentiate the efficiency of low-dose 5-FU in treating HCC.
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Affiliation(s)
- Xu-Zheng Chen
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, and Hospital of Fujian Agriculture and Forestry University, Fuzhou 350108, PR China
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Zhang YY, Li X, Qian SW, Guo L, Huang HY, He Q, Liu Y, Ma CG, Tang QQ. Transcriptional activation of histone H4 by C/EBPβ during the mitotic clonal expansion of 3T3-L1 adipocyte differentiation. Mol Biol Cell 2011; 22:2165-74. [PMID: 21562223 PMCID: PMC3128520 DOI: 10.1091/mbc.e10-11-0912] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Histone H4 is activated by C/EBPβ in mitotic clonal expansion during adipogenesis. C/EBP-binding sites are identified in histone H4 promoters, and H4 expression is suppressed when C/EBPβ is knocked down or its DNA-binding activity is inhibited by A-C/EBP. These results help in our understanding of how C/EBPβ plays important roles in the proliferation of other cells. CCAAT enhancer binding protein β (C/EBPβ) is required for both mitotic clonal expansion (MCE) and terminal differentiation during the 3T3-L1 adipocyte differentiation program. Whereas the mechanism of C/EBPβ during terminal differentiation is well understood, the mechanism of C/EBPβ in MCE is not. We provide evidence that histone H4, the most conserved cell cycle–related histone, the change of which is strictly correlated with DNA content change during the cell cycle, is transcriptionally activated by C/EBPβ during MCE. Expression of histone H4 is increased at 16 h after induction when 3T3-L1 preadipocytes synchronously reenter S phase, which is correlated with the sequential phosphorylation and activation of C/EBPβ, and expression was partially suppressed when A-C/EBP (dominant negative for C/EBP protein) was overexpressed. One C/EBP-binding site was identified in one of the histone H4 gene promoters (hist4h4), confirmed by both electrophoretic mobility shift assay and chromatin immunoprecipitation assay. C/EBP-binding sites were also found in 9 of 11 other histone H4 promoters, which can also be transactivated by C/EBPβ. Knockdown of C/EBPβ by stealth small interfering RNA partially decreased H4 gene expression and arrested cells in G1 phase as indicated by bromodeoxyuridine incorporation and fluorescence-activated cell sorting analysis of DNA content. This study provides new insights into why C/EBPβ is required for MCE during 3T3-L1 adipocyte differentiation and why C/EBPβ plays important roles in the proliferation of other cell types.
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Affiliation(s)
- You-You Zhang
- The Key Laboratory of Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai 200032, China
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Marcote MJ, Pagano M, Draetta G. cdc2 protein kinase: structure-function relationships. CIBA FOUNDATION SYMPOSIUM 2007; 170:30-41; discussion 41-9. [PMID: 1483349 DOI: 10.1002/9780470514320.ch4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Activation of the cdc2 kinase in the cell cycle occurs upon binding to a regulatory subunit called cyclin. Cyclin A associates with both Cdc2 and its homologue Cdk2. The two complexes appear in S phase but cyclin A/Cdk2 is activated earlier than cyclin A/Cdc2. Several regions in Cdc2 are involved in binding cyclins A and B. Phosphorylation of cyclin/Cdk complexes ensures that the kinase activity peaks at a specific time in the cell cycle. Phosphorylation of Thr161 in Cdc2 is required for strong cyclin binding and kinase activity in vitro; its dephosphorylation is necessary for cells to exit mitosis. We have identified a novel 'Activating factor' that stimulates binding between cyclin and Cdc2 by inducing phosphorylation of Cdc2 on Thr161. We propose that Thr161 is targeted by an additional cell cycle regulatory pathway.
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Affiliation(s)
- M J Marcote
- Differentiation Programme, European Molecular Biology Laboratory, Heidelberg, Germany
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Stillman B, Bell SP, Dutta A, Marahrens Y. DNA replication and the cell cycle. CIBA FOUNDATION SYMPOSIUM 2007; 170:147-56; discussion 156-60. [PMID: 1336449 DOI: 10.1002/9780470514320.ch10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The replication of DNA in the eukaryotic cell cycle is one of the most highly regulated events in cell growth and division. Biochemical studies on the replication of the genome of the small DNA virus simian virus 40 (SV40) have resulted in the identification of a number of DNA replication proteins from human cells. One of these, Replication Protein A (RPA), was phosphorylated in a cell cycle-dependent manner, beginning at the onset of DNA replication. RPA was phosphorylated in vitro by the cell cycle-regulated cdc2 protein kinase. This kinase also stimulated the unwinding of the SV40 origin of DNA replication during initiation of DNA replication in vitro, suggesting a mechanism by which cdc2 kinase may regulate DNA replication. Functional homologues of the DNA replication factors have been identified in extracts from the yeast Saccharomyces cerevisiae, enabling a genetic characterization of the role of these proteins in the replication of cellular DNA. A cellular origin binding protein had not been characterized. To identify proteins that function like T antigen at cellular origins of DNA replication, we examined the structure of a yeast origin of DNA replication in detail. This origin consists of four separate functional elements, one of which is essential. A multiprotein complex that binds to the essential element has been identified and purified. This protein complex binds to all known cellular origins from S. cerevisiae and may function as an origin recognition complex.
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Affiliation(s)
- B Stillman
- Cold Spring Harbor Laboratory, New York 11724
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Tanaka S, Tak YS, Araki H. The role of CDK in the initiation step of DNA replication in eukaryotes. Cell Div 2007; 2:16. [PMID: 17547773 PMCID: PMC1899495 DOI: 10.1186/1747-1028-2-16] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Accepted: 06/05/2007] [Indexed: 11/21/2022] Open
Abstract
Cyclin-dependent kinases (CDKs) regulate the progression of the cell cycle in eukaryotes. One of the major roles of CDK is to promote chromosomal DNA replication. However, how CDKs promote DNA replication has been a long-standing question, because all the essential CDK substrates in DNA replication have not been identified yet. Recently Sld2 and Sld3 were identified as essential substrates of CDKs in the initiation step of DNA replication in budding yeast. Moreover, bypass of their phosphorylations is sufficient to promote DNA replication. Phosphorylation of Sld2 and Sld3 by CDKs enhances the formation of complex(es) with a BRCT (BRCA1 C-Terminal)-containing replication protein, Dpb11. We further propose that multiple phosphorylation by CDKs controls this process in budding yeast. Even though Sld3 orthologues in multicellular eukaryotes have not been identified, similar complex formation and, therefore, a similar mechanism of initiation control might be employed in eukaryotes.
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Affiliation(s)
- Seiji Tanaka
- Division of Microbial Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Shizuoka, Japan
- Department of Genetics, SOKENDAI, Mishima, Shizuoka, Japan
- CREST, Kawaguchi, Saitama, Japan
| | - Yon-Soo Tak
- Department of Biological Sciences, KAIST, Daejeon, Korea
| | - Hiroyuki Araki
- Division of Microbial Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Shizuoka, Japan
- Department of Genetics, SOKENDAI, Mishima, Shizuoka, Japan
- CREST, Kawaguchi, Saitama, Japan
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11
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Affiliation(s)
- C Norbury
- ICRF Cell Cycle Group, Microbiology Unit, Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK
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Ozawa H, Ashizawa S, Naito M, Yanagihara M, Ohnishi N, Maeda T, Matsuda Y, Jo Y, Higashi H, Kakita A, Hatakeyama M. Paired-like homeodomain protein ESXR1 possesses a cleavable C-terminal region that inhibits cyclin degradation. Oncogene 2004; 23:6590-602. [PMID: 15235584 DOI: 10.1038/sj.onc.1207884] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The eukaryotic cell cycle is regulated by sequential activation and inactivation of cyclin-cyclin-dependent kinase (Cdk) complexes. In this work, we screened human cDNAs that can rescue yeast Saccharomyces cerevisiae from lethality caused by ectopic expression of human cyclin E and isolated a cDNA encoding ESXR1, a paired-like homeodomain-containing protein with a unique C-terminal proline-rich repeat region. In adult tissues, ESXR1 is primarily expressed in the testis. We demonstrate that ESXR1 prevents degradation of ubiquitinated cyclins in human cells. Accordingly, elevation of ESXR1 level results in accumulation of cyclin A and cyclin B1 and thereby provokes M-phase arrest. In human cells, the 65-kDa full-length ESXR1 protein is capable of proteolytically processing into N-terminal 45-kDa and C-terminal 20-kDa fragments. The C-terminal fragment, containing a proline-rich repeat region, is localized to the cytoplasm and displays the ability to inhibit cyclin degradation. In contrast, the N-terminal fragment, containing a paired-like homeodomain, is localized exclusively in the nucleus, suggesting that it plays a role in transcription. Our results indicate that proteolytic processing of ESXR1 plays a role in concerted regulation of the cell cycle and transcription in human cells.
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Affiliation(s)
- Heita Ozawa
- Division of Molecular Oncology, Institute for Genetic Medicine and Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0815, Japan
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Willmarth NE, Albertson DG, Ethier SP. Chromosomal instability and lack of cyclin E regulation in hCdc4 mutant human breast cancer cells. Breast Cancer Res 2004; 6:R531-9. [PMID: 15318934 PMCID: PMC549168 DOI: 10.1186/bcr900] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 05/14/2004] [Accepted: 05/26/2004] [Indexed: 11/10/2022] Open
Abstract
Introduction Cyclin E, a G1 cyclin essential for G1–S phase transition, is known to have a profound effect on tumorigenesis. Elevated levels of cyclin E have been associated with breast cancer, and chromosomal instability observed in breast cancer is suggested to be associated with constitutive expression of cyclin E. It was previously demonstrated that SUM149PT human breast cancer cells show very high levels of cyclin E expression by western analysis and that they express a nonfunctional cyclin E ubiquitin ligase due to a mutation in the F-box protein hCdc4. Methods We examined cyclin E expression in both MCF10A and SUM149PT cells using western blot analysis and flow cytometry. Immunofluorescence was utilized for the localization of cyclin E in both normal and breast cancer cells. In addition, array comparative genomic hybridization analysis was performed to compare chromosome copy number alterations with levels of cyclin E expression among a panel of breast cancer cell lines. Results SUM149PT cells overexpress cyclin E on a cell per cell basis for the duration of the cell cycle. High cyclin E levels are maintained throughout the S phase, and SUM149PT cells exhibit an S phase delay or arrest probably due to cyclin E overexpression. In addition, comparative genomic hybridization indicated that SUM149PT cells exhibit many chromosome copy number alterations, which may reflect prior or ongoing genomic instability. However, no direct correlation was observed between cyclin E levels and genomic copy number alteration in a panel of human breast cancer cell lines. Conclusions Cyclin E is overexpressed at high levels throughout the cell cycle in SUM149PT cells, which is in stark contrast to cyclin E degradation observed in the mid to late S phase of normal cells. SUM149PT cells are unable to regulate cyclin E and also exhibit many copy number alterations. However, there was a lack of direct correlation between cyclin E overexpression and chromosomal instability across a panel of other breast cancer cell lines examined.
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Affiliation(s)
- Nicole E Willmarth
- Department of Cellular and Molecular Biology, The University of Michigan, Ann Arbor, Michigan, USA
- Department of Radiation Oncology, Division of Radiation and Cancer Biology, The University of Michigan Health System, and the University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan, USA
| | - Donna G Albertson
- Cancer Research Institute, University of California San Francisco, San Francisco, California, USA
| | - Stephen P Ethier
- Department of Radiation Oncology, Division of Radiation and Cancer Biology, The University of Michigan Health System, and the University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan, USA
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Abstract
BACKGROUND Cyclin-dependent kinases (Cdks) and their cyclin regulatory subunits control cell growth and division. Cdk2/cyclin E complexes are thought to be required because they phosphorylate the retinoblastoma protein and drive cells through the G1/S transition into the S phase of the cell cycle. In addition, Cdk2 associates with cyclin A, which itself is essential for cell proliferation during early embryonic development. RESULTS In order to study the functions of Cdk2 in vivo, we generated Cdk2 knockout mice. Surprisingly, these mice are viable, and therefore Cdk2 is not an essential gene in the mouse. However, Cdk2 is required for germ cell development; both male and female Cdk2(-/-) mice are sterile. Immunoprecipitates of cyclin E1 complexes from Cdk2(-/-) spleen extracts displayed no activity toward histone H1. Cyclin A2 complexes were active in primary mouse embryonic fibroblasts (MEFs), embryo extracts and in spleen extracts from young animals. In contrast, there was little cyclin A2 kinase activity in immortalized MEFs and spleen extracts from adult animals. Cdk2(-/-) MEFs proliferate but enter delayed into S phase. Ectopic expression of Cdk2 in Cdk2(-/-) MEFs rescued the delayed entry into S phase. CONCLUSIONS Although Cdk2 is not an essential gene in the mouse, it is required for germ cell development and meiosis. Loss of Cdk2 affects the timing of S phase, suggesting that Cdk2 is involved in regulating progression through the mitotic cell cycle.
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Affiliation(s)
- Cyril Berthet
- Regulation of Cell Growth Laboratory, National Cancer Institute, Building 560, 1050 Boyles St., Frederick, MD 21702-1201, USA
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Mazumder S, DuPree E, Almasan A. A Dual Role of Cyclin E in Cell Proliferation and Apotosis May Provide a Target for Cancer Therapy. Curr Cancer Drug Targets 2004; 4:65-75. [PMID: 14965268 PMCID: PMC1307511 DOI: 10.2174/1568009043481669] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cyclin E is essential for progression through the G1-phase of the cell cycle and initiation of DNA replication by interacting with and activating its catalytic partner, the cyclin dependent kinase 2 (Cdk2). Rb, as well as Cdc6, NPAT, and nucleophosmin, critical components of cell proliferation and DNA replication, respectively, are targets of Cyclin E/Cdk2 phosphorylation. There are a number of putative binding sites for E2F in the cyclin E promoter region, suggesting an E2F-dependent regulation. Skp2 and Fbw7 are novel proteins, responsible for ubiquitin-dependent proteolysis of Cyclin E. The tight regulation of cyclin E expression, both at the transcriptional level and by ubiquitin-mediated proteolysis, indicates that it has a major role in the control of the G1- and S-phase transitions. Cyclin E is also transcriptionally regulated during radiation-induced apoptosis of hematopoietic cells. In addition to its biological roles, deregulated cyclin E expression has an established role in tumorigenesis. Cell cycle regulatory molecules, such as cyclin E, are frequently deregulated in different types of cancers, where overexpressed native or low molecular weight forms of Cyclin E have a significant role in oncogenesis. During apoptosis of hematopoietic cells, caspase-dependent proteolysis of Cyclin E generates a p18-Cyclin E variant. Understanding the role of Cyclin E in apoptosis may provide a novel target, which may be effective in cancer therapy. This review summarizes what is known about the biological role of cyclin E, its deregulation in cancer, and the opportunities it may provide as a target in clinical therapy.
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Affiliation(s)
- S. Mazumder
- Department of Cancer Biology, Lerner Research Institute
| | - E.L. DuPree
- Department of Chemistry, Cleveland State University, Cleveland, OH 44115, USA
| | - A. Almasan
- Department of Cancer Biology, Lerner Research Institute
- Department of Radiation Oncology, The Cleveland Clinic Foundation, Cleveland, OH 44195, and
- Department of Chemistry, Cleveland State University, Cleveland, OH 44115, USA
- *Address correspondence to this author at the Departments of Cancer Biology and Radiation Oncology, Lerner Research Institute, NB40, Cleveland Clinic Foundation, Cleveland, OH 44195, USA; Tel.: 216-444-9970; Fax: 216-445-6269; E-mail:
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Abstract
Human mammary epithelial cells emerge spontaneously from senescence, exhibiting eroding telomeric sequences, and ultimately enter crisis to generate the type of chromosomal abnormalities seen in early stages of breast cancer. In a mouse mammary tumor model, the spontaneous escape of senescence can be observed as an increase in DNA synthesis that is reflected by alterations in the cell cycle profile and increases in the expression levels and activities of cell cycle molecular components. This review provides an overview of gene alterations in the cell cycle components in mouse mammary hyperplasia.
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Affiliation(s)
- Thenaa K Said
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
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Park Y, Ng C, Datta S. Induction of string rescues the neuroblast proliferation defect in trol mutant animals. Genesis 2003; 36:187-95. [PMID: 12929089 DOI: 10.1002/gene.10216] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In trol mutants, neuroblasts fail to exit G1 for S phase. Increasing string expression in trol mutants rescues the number of S phase neuroblasts without an increase in M phase neuroblasts. Decreasing string expression further decreased the number of S phase neuroblasts. Coexpression of cyclin E and string did not produce additional S phase cells. Unlike cyclin E, cdk2, and cdk2AF, elevated expression of neither cyclin A, cyclin D, nor cdk1AF was able to promote S phase progression in arrested neuroblasts, indicating that String-induced activity of a Cyclin A or Cyclin D complex is unlikely to drive trol neuroblasts into S phase. Biochemical analyses revealed a rapid increase of Cyclin E-Cdk2 kinase activity to wild-type levels upon increased string expression. These results suggest that Drosophila Cdc25 may directly or indirectly increase the kinase activity of Cyclin E-Cdk2 complexes in vivo, thus driving arrested neuroblasts into cell division.
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Affiliation(s)
- Youngji Park
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
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Padmanabhan R, Tanimoto A, Sasaguri Y. Transactivation of human cdc2 promoter by adenovirus E1A. Curr Top Microbiol Immunol 2003; 272:365-97. [PMID: 12747556 DOI: 10.1007/978-3-662-05597-7_12] [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: 01/14/2023]
Abstract
Expression of the adenovirus oncoprotein E1A 12S induces the heterotrimeric transcription factor, NF-Y. NF-Y binds to the two CCAAT motifs upstream of the transcriptional start site of the human cdc2 promoter and is required for activation of the promoter by E1A 12S in cycling cells. The observations that a number of eukaryotic cell cycle regulatory genes also contain the CCAAT motifs and NF-Y binds to them support the notion that E1A 12S could play an important role in deregulated expression of these genes through activation of NF-Y gene in cycling cells.
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Affiliation(s)
- R Padmanabhan
- Department of Microbiology and Immunology, Georgetown University Medical Center, 3900 Reservoir Road, Washington DC, WA 20057, USA.
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19
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Cheng IH, Roberts LA, Tye BK. Mcm3 is polyubiquitinated during mitosis before establishment of the pre-replication complex. J Biol Chem 2002; 277:41706-14. [PMID: 12200430 DOI: 10.1074/jbc.m205793200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
To ensure fidelity in genome duplication, eukaryotes restrict DNA synthesis to once every cell division by a cascade of regulated steps. Central to this cascade is the periodic assembly of the hexameric MCM2-7 complex at replication origins. However, in Saccharomyces cerevisiae, only a fraction of each MCM protein is able to assemble into hexamers and associate with replication origins during M phase, suggesting that MCM complex assembly and recruitment may be regulated post-translationally. Here we show that a small fraction of Mcm3p is polyubiquitinated at the onset of MCM complex assembly. Reducing the rate of ubiquitination by uba1-165, a suppressor of mcm3-10, restored the interaction of Mcm3-10p with subunits of the MCM complex and its recruitment to the replication origin. Possible roles for ubiquitinated Mcm3p in the assembly of the MCM complex at replication origins are discussed.
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Affiliation(s)
- Irene H Cheng
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703, USA
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20
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Lenz HJ, Anderson WF, Hall FL, Gordon EM. Clinical protocol. Tumor site specific phase I evaluation of safety and efficacy of hepatic arterial infusion of a matrix-targeted retroviral vector bearing a dominant negative cyclin G1 construct as intervention for colorectal carcinoma metastatic to liver. Hum Gene Ther 2002; 13:1515-37. [PMID: 12215272 DOI: 10.1089/10430340260185148] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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21
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Calzada A, Bueno A. Genes involved in the initiation of DNA replication in yeast. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 212:133-207. [PMID: 11804036 DOI: 10.1016/s0074-7696(01)12005-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Replication and segregation of the information contained in genomic DNA are strictly regulated processes that eukaryotic cells alternate to divide successfully. Experimental work on yeast has suggested that this alternation is achieved through oscillations in the activity of a serine/threonine kinase complex, CDK, which ensures the timely activation of DNA synthesis. At the same time, this CDK-mediated activation sets up the basis of the mechanism that ensures ploidy maintenance in eukaryotes. DNA synthesis is initiated at discrete sites of the genome called origins of replication on which a prereplicative complex (pre-RC) of different protein subunits is formed during the G1 phase of the cell division cycle. Only after pre-RCs are formed is the genome competent to be replicated. Several lines of evidence suggest that CDK activity prevents the assembly of pre-RCs ensuring single rounds of genome replication during each cell division cycle. This review offers a descriptive discussion of the main molecular events that a unicellular eukaryote such as the budding yeast Saccharomyces cerevisiae undergoes to initiate DNA replication.
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Affiliation(s)
- Arturo Calzada
- Instituto de Microbiología--Bioquímica/Centro de Investigación del Cancer, Departamento de Microbiología y Genética, Edificio Departamental, CSIC/Universidad de Salamanca, Spain
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22
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Nakashima T, Masuda A, Sekiguchi T, Nishimoto T, Uemura T. Preliminary findings of chromosomal alterations and expression of cell cycle genes in head an neck tumors. Eur Arch Otorhinolaryngol 2002; 251 Suppl 1:S87-90. [PMID: 11894785 DOI: 10.1007/bf02565228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The genesis and progression of malignant tumors may be related to certain somatic mutations and the accumulation of multiple chromosomal alterations. Using four freshly resected malignant tumors, we investigated the relationship between chromosomal alteration and expression of cell cycle regulatory genes. Specimens of thyroid hyperplasia and normal thyroid tissue were also investigated. As cell cycle regulating genes, we chose the cdc2 gene that encodes the p34cdc2 protein kinase, a major kinase of the cell cycle, and the RCC1 gene that is essential for coupling between S and M phases. Three of the malignant tumors contained cells with chromosomal alterations, including one polyploid and two aneuploid. The DNA content of cells in thyroid hyperplasia was the same as in the normal gland. The amount of p34cdc2 protein was very low in cells of both normal thyroid and hyperplastic tissue, and grew very slowly as compared with malignant tumors. There was no significant relationship between the amount of RCC1 and ploidy pattern.
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Affiliation(s)
- T Nakashima
- Department of Otorhinolaryngology, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka, 812, Japan
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23
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Strube RW, Chen SY. Characterization of anti-cyclin E single-chain Fv antibodies and intrabodies in breast cancer cells: enhanced intracellular stability of novel sFv-F(c) intrabodies. J Immunol Methods 2002; 263:149-67. [PMID: 12009211 DOI: 10.1016/s0022-1759(02)00035-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Cyclin E is a critical cell cycle protein in the regulated progression of normal cells to replicate their DNA. Ectopic overexpression of cyclin E results in accelerated G(1) progression, chromosome instability, and a reduced requirement for growth factors. Dysregulated cyclin E expression is found in nearly all breast cancers examined. Toward the goal of developing a system to block cyclin E function in normal and breast cancer cells, we have developed anti-cyclin E single-chain antibodies (sFvs) for use as intrabodies. We have cloned the variable region genes from two hybridoma cell lines that produce anti-human cyclin E antibodies, linked them into sFvs, and showed their ability to bind cyclin E when expressed as sFv-F(c) fusion proteins. Engineering of the sFvs as sFv-F(c) intrabodies resulted in a dramatic increase in the sFv half-life as analyzed by pulse-chase and immunofluorescence, and these fusion intrabodies can be expressed in the cytosol or retargeted to the nucleus of breast cancer cell lines. Stable expression of a nuclear-targeted anti-cyclin E intrabody appears to inhibit the growth of the breast cancer cell line SKBR3. This work sets the stage for the development of intrabody-based inducible or tissue-specific cyclin E knockouts and for identifying cyclin E and its vital cell cycle functions as a potential gene therapy target in breast and other cancers.
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Affiliation(s)
- Randall W Strube
- Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC 27109, USA
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24
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Badea T, Niculescu F, Soane L, Fosbrink M, Sorana H, Rus V, Shin ML, Rus H. RGC-32 increases p34CDC2 kinase activity and entry of aortic smooth muscle cells into S-phase. J Biol Chem 2002; 277:502-8. [PMID: 11687586 DOI: 10.1074/jbc.m109354200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proliferation of aortic smooth muscle cells contributes to atherogenesis and neointima formation. Sublytic activation of complement, particularly C5b-9, induces cell cycle progression in aortic smooth muscle cells. RGC-32 is a novel protein that may promote cell cycle progression in response to complement activation. We cloned human RGC-32 cDNA from a human fetal brain cDNA library. The human RGC-32 cDNA encodes a 117-amino acid protein with 92% similarity to the rat and mouse protein. Human RGC-32 maps to chromosome 13 and is expressed in most tissues. Sublytic complement activation enhanced RGC-32 mRNA expression in human aortic smooth muscle cells and induced nuclear translocation of the protein. RGC-32 was physically associated with cyclin-dependent kinase p34CDC2 and increased the kinase activity in vivo and in vitro. In addition, RGC-32 was phosphorylated by p34CDC2-cyclin B1 in vitro. Mutation of RGC-32 protein at Thr-91 prevented the p34CDC2-mediated phosphorylation and resulted in loss of p34CDC2 kinase enhancing activity. Overexpression of RGC-32 induced quiescent aortic smooth muscle cells to enter S-phase. These data indicate that cell cycle activation by C5b-9 may involve p34CDC2 activity through RGC-32. RGC-32 appears to be a cell cycle regulatory factor that mediates cell proliferation, both as an activator and substrate of p34CDC2.
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Affiliation(s)
- Tudor Badea
- University of Maryland School of Medicine, the Department of Pathology, Baltimore, Maryland 21201, USA
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25
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Bashir T, Rommelaere J, Cziepluch C. In vivo accumulation of cyclin A and cellular replication factors in autonomous parvovirus minute virus of mice-associated replication bodies. J Virol 2001; 75:4394-8. [PMID: 11287588 PMCID: PMC114184 DOI: 10.1128/jvi.75.9.4394-4398.2001] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Autonomous parvovirus minute virus of mice (MVM) DNA replication is strictly dependent on cellular factors expressed during the S phase of the cell cycle. Here we report that MVM DNA replication proceeds in specific nuclear structures termed autonomous parvovirus-associated replication bodies, where components of the basic cellular replication machinery accumulate. The presence of DNA polymerases alpha and delta in these bodies suggests that MVM utilizes partially preformed cellular replication complexes for its replication. The recruitment of cyclin A points to a role for this cell cycle factor in MVM DNA replication beyond its involvement in activating the conversion of virion single-stranded DNA to the duplex replicative form.
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Affiliation(s)
- T Bashir
- Applied Tumor Virology Unit F0100 and Institut National de la Santé et de la Recherche Médicale U 375, Deutsches Krebsforschungszentrum, D-69120 Heidelberg, Germany
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26
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Groth A, Weber JD, Willumsen BM, Sherr CJ, Roussel MF. Oncogenic Ras Induces p19ARF and Growth Arrest in Mouse Embryo Fibroblasts Lacking p21Cip1 and p27Kip1 without Activating Cyclin D-dependent Kinases. J Biol Chem 2000. [DOI: 10.1016/s0021-9258(19)61532-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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27
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Tatsuno I, Hirai A, Saito Y. Cell-anchorage, cell cytoskeleton, and Rho-GTPase family in regulation of cell cycle progression. PROGRESS IN CELL CYCLE RESEARCH 2000; 4:19-25. [PMID: 10740811 DOI: 10.1007/978-1-4615-4253-7_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
It has been well known that cell-anchorage and the cell cytoskeleton are deeply involved in the regulation of cell proliferation and cell cycle. However, the precise molecular mechanism involved in cell-anchorage and the cell cytoskeleton have remained be to elucidated. The recent great volume of information regarding cell cycle regulators such as cyclin, cyclin-dependent kinases (CDKs) and CDK inhibitors (CKI) has facilitated the understanding of the cell cycle in mammalian cells. In this review, we will focus on these cell cycle regulators to discuss the regulation of cell proliferation controlled by cell-anchorage and the cytoskeleton, and especially the roles of Rho family GTPases.
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Affiliation(s)
- I Tatsuno
- Second Department of Internal Medicine, Chiba University School of Medicine, Japan
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28
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Hirohata S, Nakanishi K, Yanagida T. Inhibition of cyclin A gene expression in human B cells by an immunosuppressant mizoribine. Clin Exp Immunol 2000; 120:448-53. [PMID: 10844522 PMCID: PMC1905568 DOI: 10.1046/j.1365-2249.2000.01242.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mizoribine has been shown to have beneficial effects in the treatment of rheumatoid arthritis and lupus nephritis, in which abnormal B cell functions are involved. Previous studies demonstrated that mizoribine directly suppresses the function of human B cells. The current study explored in detail the mechanism of the suppression of human B cell responses by mizoribine at the molecular level. Highly purified peripheral blood B cells obtained from normal healthy individuals were stimulated with Staphylococcus aureus Cowan I (SAC) plus IL-2 in the presence or absence of mizoribine or methotrexate for 48 h to 72 h. The expression of cyclin A mRNA was determined by semiquantitative reverse transcriptase-polymerase chain reaction followed by Southern hybridization. Although at pharmacologically attainable concentrations both mizoribine and methotrexate suppressed the production of IgM of SAC-activated B cells, mizoribine, but not methotrexate, decreased the expression of cyclin A protein as well as mRNA in B cells stimulated with SAC + IL-2. Of note, mizoribine facilitated the degradation of cyclin A mRNA in the presence of actinomycin D, indicating that mizoribine shortens the stability of cyclin A mRNA. The results indicate that mizoribine suppresses the expression of cyclin A mRNA in human B cells by down-regulating its stability, and thus down-regulates their responses.
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Affiliation(s)
- S Hirohata
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan.
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29
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Yoshida N, Yamashita M. Non-dependence of cyclin E/Cdk2 kinase activity on the initiation of oocyte maturation in goldfish. Dev Growth Differ 2000; 42:285-94. [PMID: 10910135 DOI: 10.1046/j.1440-169x.2000.00506.x] [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: 11/20/2022]
Abstract
Cdk2 kinase activity increases during oocyte maturation but neither cyclin A nor B is associated with Cdk2 in mature oocytes in goldfish. As a potential Cdk2 partner in meiosis, a cyclin E homolog was isolated from a goldfish oocyte cDNA library. A monoclonal antibody was raised against bacterially produced full-length goldfish cyclin E. Both cyclin E and Cdk2 were already present in immature oocytes and their protein levels did not change remarkably during oocyte maturation. Cyclin E formed a complex mainly with Cdk2 just at the time of germinal vesicle breakdown (GVBD) in association with the increase in Cdk2 kinase activity, although a fraction of cyclin E bound to Cdk(s) other than Cdk2 and Cdc2. Ectopic activation of cyclin E/Cdk2 by the injection of cyclin E messenger RNA (mRNA) into immature oocytes did not induce maturation-promoting factor (MPF) activation and GVBD. Furthermore, inhibition of cyclin E/Cdk2 kinase activity by the injection of p21SDI1 into the oocytes treated with 17alpha,20beta-dihydroxy-4-pregnen-3-one had no effect on MPF activation and GVBD. These results indicate that cyclin E/Cdk2 kinase activity is insufficient and unnecessary for initiating goldfish oocyte maturation.
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Affiliation(s)
- N Yoshida
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan
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30
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Bashir T, Horlein R, Rommelaere J, Willwand K. Cyclin A activates the DNA polymerase delta -dependent elongation machinery in vitro: A parvovirus DNA replication model. Proc Natl Acad Sci U S A 2000; 97:5522-7. [PMID: 10792046 PMCID: PMC25861 DOI: 10.1073/pnas.090485297] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Replication of the single-stranded linear DNA genome of parvovirus minute virus of mice (MVM) starts with complementary strand synthesis from the 3'-terminal snap-back telomere, which serves as a primer for the formation of double-stranded replicative form (RF) DNA. This DNA elongation reaction, designated conversion, is exclusively dependent on cellular factors. In cell extracts, we found that complementary strand synthesis was inhibited by the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) and rescued by the addition of proliferating cell nuclear antigen, arguing for the involvement of DNA polymerase (Pol) delta in the conversion reaction. In vivo time course analyses using synchronized MVM-infected A9 cells allowed initial detection of MVM RF DNA at the G(1)/S phase transition, coinciding with the onset of cyclin A expression and cyclin A-associated kinase activity. Under in vitro conditions, formation of RF DNA was efficiently supported by A9 S cell extracts, but only marginally by G(1) cell extracts. Addition of recombinant cyclin A stimulated DNA conversion in G(1) cell extracts, and correlated with a concomitant increase in cyclin A-associated kinase activity. Conversely, a specific antibody neutralizing cyclin A-dependent kinase activity, abolished the capacity of S cell extracts for DNA conversion. We found no evidence for the involvement of cyclin E in the regulation of the conversion reaction. We conclude that cyclin A is necessary for activation of complementary strand synthesis, which we propose as a model reaction to study the cell cycle regulation of the Pol delta-dependent elongation machinery.
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Affiliation(s)
- T Bashir
- Deutsches Krebsforschungszentrum, Department of Applied Tumor Virology, Abt. F0100 and Formation Institut National de la Santé et de la Recherche Médicale (INSERM) U375, Heidelberg, Germany
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31
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Lilly MA, de Cuevas M, Spradling AC. Cyclin A associates with the fusome during germline cyst formation in the Drosophila ovary. Dev Biol 2000; 218:53-63. [PMID: 10644410 DOI: 10.1006/dbio.1999.9570] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulated changes in the cell cycle underlie many aspects of growth and differentiation. Prior to meiosis, germ cell cycles in many organisms become accelerated, synchronized, and modified to lack cytokinesis. These changes cause cysts of interconnected germ cells to form that typically contain 2(n) cells. In Drosophila, developing germ cells during this period contain a distinctive organelle, the fusome, that is required for normal cyst formation. We find that the cell cycle regulator Cyclin A transiently associates with the fusome during the cystocyte cell cycles, suggesting that fusome-associated Cyclin A drives the interconnected cells within each cyst synchronously into mitosis. In the presence of a normal fusome, overexpression of Cyclin A forces cysts through an extra round of cell division to produce cysts with 32 germline cells. Female sterile mutations in UbcD1, encoding an E2 ubiquitin-conjugating enzyme, have a similar effect. Our observations suggest that programmed changes in the expression and cytoplasmic localization of key cell cycle regulatory proteins control germline cyst production.
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Affiliation(s)
- M A Lilly
- Department of Embryology, Howard Hughes Medical Institute, Carnegie Institution of Washington, 115 West University Parkway, Baltimore, Maryland, 21210, USA
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32
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Ohtoshi A, Maeda T, Higashi H, Ashizawa S, Yamada M, Hatakeyama M. beta3-endonexin as a novel inhibitor of cyclin A-associated kinase. Biochem Biophys Res Commun 2000; 267:947-52. [PMID: 10673397 DOI: 10.1006/bbrc.1999.2007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cyclin A is indispensable for S phase cell cycle progression and is suggested to be a crucial target of cell adhesion signals. In this study, we demonstrate that beta3-endonexin, a molecule known to associate with the integrin beta3 cytoplasmic domain, specifically binds cyclin A. Deletion of the amino-terminal 52-amino-acid residues including the cyclin-binding RxL motif abolishes the ability of beta3-endonexin to interact with cyclin A. In an in vitro kinase assay, beta3-endonexin inhibits pRB kinase activity associated with cyclin A-Cdk2 while leaving its histone H1 kinase activity unaffected. Coexpression of beta3-endonexin in yeast cells overcomes growth suppression caused by an activation of cyclin A-associated kinase. Our results indicate that beta3-endonexin is a novel cyclin A-binding molecule that regulates cyclin A-associated pRB kinase activity.
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Affiliation(s)
- A Ohtoshi
- Department of Viral Oncology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, 170-8455, Japan
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33
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Kampmeier J, Behrens A, Wang Y, Yee A, Anderson WF, Hall FL, Gordon EM, McDonnell PJ. Inhibition of rabbit keratocyte and human fetal lens epithelial cell proliferation by retrovirus-mediated transfer of antisense cyclin G1 and antisense MAT1 constructs. Hum Gene Ther 2000; 11:1-8. [PMID: 10646634 DOI: 10.1089/10430340050016102] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The aim of this study is to evaluate the potential of gene transfer of cell cycle control genes as treatment of corneal haze or secondary cataract formation. The guiding hypothesis is that strategic modulation of the cyclin G1 or MAT1 gene by retrovirus-mediated gene transfer will inhibit proliferation of rabbit keratocytes (RabK) and fetal human lens epithelial (FHLEpi) cells in vitro. RabK and FHLEpi cell cultures were transduced in triplicate with retroviral vectors bearing either a nuclear-targeted beta-galactosidase, an antisense cyclin G1 (aG1), an antisense MAT1 (aMAT1) construct, or the neo(r) gene. The presence of beta-galactosidase activity in the transduced cultures was detected by immunohistochemical X-Gal staining, while cyclin G1 and MAT1 protein expression levels were evaluated by Western analysis. Proliferation of RabKs and FHLEpi cells was analyzed by counting the number of cells in the aG1 and aMAT1 vector-transduced cultures over 5 days. The mean transduction efficiency was 34.4% (SD 1.41) for RabKs and 19.7% (SD 1.83) for FHLEpi cells. Downregulation of cyclin G1 and MAT1 protein expression was noted 24 hr after transduction of RabK cultures with the respective vectors. Cytostatic effects of the aG1 and aMAT1 vectors in both RabKs and FHLEpi cells were most pronounced on the fifth day (RabKs, p < 0.0007; FHEpi cells, p < 0.001). An increased incidence of apoptosis was identified in both aG1 and MAT1-transduced FHLEpi cells. Taken together, these data suggest the potential utility of developing aG1 and aMAT1 retroviral vectors in gene therapy protocols for corneal haze and secondary cataract formation.
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Affiliation(s)
- J Kampmeier
- Doheny Eye Institute and Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles 90033, USA
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34
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Grifman M, Chen NN, Gao GP, Cathomen T, Wilson JM, Weitzman MD. Overexpression of cyclin A inhibits augmentation of recombinant adeno-associated virus transduction by the adenovirus E4orf6 protein. J Virol 1999; 73:10010-9. [PMID: 10559315 PMCID: PMC113052 DOI: 10.1128/jvi.73.12.10010-10019.1999] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 34-kDa product of adenovirus E4 region open reading frame 6 (E4orf6) dramatically enhances transduction by recombinant adeno-associated virus vectors (rAAV). This is achieved by promoting the conversion of incoming single-stranded viral genomes into transcriptionally competent duplex molecules. The molecular mechanism for enhancing second-strand synthesis is not fully understood. In this study, we analyzed the cellular consequences of E4orf6 expression and the requirements for efficient rAAV transduction mediated by E4orf6. Expression of E4orf6 in 293 cells led to an inhibition of cell cycle progression and an accumulation of cells in S phase. This was preceded by specific degradation of cyclin A and p53, while the levels of other proteins involved in cell cycle control remained unchanged. In addition, the kinase activity of cdc2 was inhibited. We further showed that p53 expression is not necessary or inhibitory for augmentation of rAAV transduction by E4orf6. However, overexpression of cyclin A inhibited E4orf6-mediated enhancement of rAAV transduction. A cyclin A mutant incapable of recruiting protein substrates for cdk2 was unable to inhibit E4orf6-mediated augmentation. In addition, we created an E4orf6 mutant that is selectively defective in rAAV augmentation of transduction. Based on these findings, we suggest that cyclin A degradation represents a viral mechanism to disrupt cell cycle progression, resulting in enhanced viral transduction. Understanding the cellular pathways used during transduction will increase the utility of rAAV vectors in a wide range of gene therapy applications.
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Affiliation(s)
- M Grifman
- Laboratory of Genetics, The Salk Institute for Biological Studies, San Diego, California 92186, USA
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35
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Abstract
We have used microinjection and time-lapse video microscopy to study the role of cyclin A in mitosis. We have injected purified, active cyclin A/cyclin-dependent kinase 2 (CDK2) into synchronized cells at specific points in the cell cycle and assayed its effect on cell division. We find that cyclin A/CDK2 will drive G2 phase cells into mitosis within 30 min of microinjection, up to 4 h before control cells enter mitosis. Often this premature mitosis is abnormal; the chromosomes do not completely condense and daughter cells fuse. Remarkably, microinjecting cyclin A/CDK2 into S phase cells has no effect on progress through the following G2 phase or mitosis. In complementary experiments we have microinjected the amino terminus of p21(Cip1/Waf1/Sdi1) (p21N) into cells to inhibit cyclin A/CDK2 activity. We find that p21N will prevent S phase or G2 phase cells from entering mitosis, and will cause early prophase cells to return to interphase. These results suggest that cyclin A/CDK2 is a rate-limiting component required for entry into mitosis, and for progress through mitosis until late prophase. They also suggest that cyclin A/CDK2 may be the target of the recently described prophase checkpoint.
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Affiliation(s)
- Nobuaki Furuno
- Wellcome/Cancer Research Campaign Institute and Department of Zoology, University of Cambridge, Cambridge CB2 1QR, United Kingdom
| | - Nicole den Elzen
- Wellcome/Cancer Research Campaign Institute and Department of Zoology, University of Cambridge, Cambridge CB2 1QR, United Kingdom
| | - Jonathon Pines
- Wellcome/Cancer Research Campaign Institute and Department of Zoology, University of Cambridge, Cambridge CB2 1QR, United Kingdom
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36
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Singer JD, Gurian-West M, Clurman B, Roberts JM. Cullin-3 targets cyclin E for ubiquitination and controls S phase in mammalian cells. Genes Dev 1999; 13:2375-87. [PMID: 10500095 PMCID: PMC317026 DOI: 10.1101/gad.13.18.2375] [Citation(s) in RCA: 321] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/1999] [Accepted: 07/30/1999] [Indexed: 11/24/2022]
Abstract
Cyclin E is an unstable protein that is degraded in a ubiquitin- and proteasome- dependent pathway. Two factors stimulate cyclin E ubiquitination in vivo: when it is free of its CDK partner, and when it is phosphorylated on threonine 380. We pursued the first of these pathways by using a two-hybrid screen to identify proteins that could bind only to free cyclin E. This resulted in the isolation of human Cul-3, a member of the cullin family of E3 ubiquitin-protein ligases. We found that Cul-3 was bound to cyclin E but not to cyclin E-Cdk2 complexes in mammalian cells, and that overexpression of Cul-3 increased ubiquitination of cyclin E but not other cyclins. Conversely, deletion of the Cul-3 gene in mice caused increased accumulation of cyclin E protein, and had cell-type-specific effects on S-phase regulation. In the extraembryonic ectoderm, in which cells undergo a standard mitotic cycle, there was a greatly increased number of cells in S phase. In the trophectoderm, in which cells go through endocycles, there was a block to entry into S phase. The SCF pathway, which targets cyclins for ubiquitination on the basis of their phosphorylation state, and the Cul-3 pathway, which selects cyclin E for ubiquitination on the basis of its assembly into CDK complexes, may be complementary ways to control cyclin abundance.
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Affiliation(s)
- J D Singer
- Division of Basic Sciences, Howard Hughes Medical Institute, Seattle, Washington 98109 USA
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37
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Findeisen M, El-Denary M, Kapitza T, Graf R, Strausfeld U. Cyclin A-dependent kinase activity affects chromatin binding of ORC, Cdc6, and MCM in egg extracts of Xenopus laevis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 264:415-26. [PMID: 10491086 DOI: 10.1046/j.1432-1327.1999.00613.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The initiation of DNA replication in eukaryotes requires the loading of the origin recognition complex (ORC), Cdc6, and minichromosome maintenance (MCM) proteins onto chromatin to form the preinitiation complex. In Xenopus egg extract, the proteins Orc1, Orc2, Cdc6, and Mcm4 are underphosphorylated in interphase and hyperphosphorylated in metaphase extract. We find that chromatin binding of ORC, Cdc6, and MCM proteins does not require cyclin-dependent kinase activities. High cyclin A-dependent kinase activity inhibits the binding and promotes the release of Xenopus ORC, Cdc6, and MCM from sperm chromatin, but has no effect on chromatin binding of control proteins. Cyclin A together with ORC, Cdc6 and MCM proteins is bound to sperm chromatin in DNA replicating pseudonuclei. In contrast, high cyclin E/cdk2 was not detected on chromatin, but was found soluble in the nucleoplasm. High cyclin E kinase activity allows the binding of Xenopus ORC and Cdc6, but not MCM, to sperm chromatin, even though the kinase does not phosphorylate MCM directly. We conclude that chromatin-bound cyclin A kinase controls DNA replication by protein phosphorylation and chromatin release of Cdc6 and MCM, whereas soluble cyclin E kinase prevents rereplication during the cell cycle by the inhibition of premature MCM chromatin association.
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Affiliation(s)
- M Findeisen
- Division of Biology, University of Konstanz, Germany
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38
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Kao CY, Tanimoto A, Arima N, Sasaguri Y, Padmanabhan R. Transactivation of the human cdc2 promoter by adenovirus E1A. E1A induces the expression and assembly of a heteromeric complex consisting of the CCAAT box binding factor, CBF/NF-Y, and a 110-kDa DNA-binding protein. J Biol Chem 1999; 274:23043-51. [PMID: 10438472 DOI: 10.1074/jbc.274.33.23043] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Cyclin-dependent kinases (CDKs) play an important role in the eukaryotic cell cycle progression. Cdc2 (CDK1) is expressed in late G(1)/S phase and required for G(2) to M phase transition in higher eukaryotes. The oncoproteins, SV40 large T antigen and adenovirus E1A, induce a 110-kDa protein which specifically recognizes the two inverted CCAAT motifs of the cdc2 promoter in cycling cells and plays an essential role in transactivation of the human cdc2 promoter. Since these CCAAT motifs also conform to the consensus binding sites for the ubiquitous heterotrimeric transcription factor, CBF/NF-Y, the role of CBF/NF-Y in the transactivation of the cdc2 promoter was examined in this study. Our results indicate that CBF/NF-Y and the 110-kDa protein interact with the CCAAT box motif to form a heteromeric complex. However, mutagenesis of the pentanucleotide CCAAT motif or in the presence of urea greater than 2.5 M, no heteromeric complex was formed. In contrast, the 110-kDa protein could still bind the mutant CCAAT motif or with the wild type motif in the presence of 2.5 M urea. Furthermore, E1A.12S induced the gene expression of all three subunits of CBF/NF-Y. Coexpression of E1A and a dominant negative mutant NF-YA subunit significantly reduced the E1A-mediated transactivation of the cdc2 promoter in a dose-dependent manner. These results support the conclusion that E1A protein mediates optimal transactivation of the human cdc2 promoter by inducing the expression and assembly of a heteromeric complex consisting of the 110-kDa protein and the CBF/NF-Y which interacts with the two CCAAT motifs of the cdc2 promoter.
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Affiliation(s)
- C Y Kao
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas 66160-7421, USA
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39
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Chin LS, Murray SF, Doherty PF, Singh SK. K252a induces cell cycle arrest and apoptosis by inhibiting Cdc2 and Cdc25c. Cancer Invest 1999; 17:391-5. [PMID: 10434949 DOI: 10.3109/07357909909021430] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The indole carbazole K252a has been shown in previous studies to inhibit the platelet-derived growth factor signal transduction pathway in gliomas. Because K252a has nonspecific effects on protein kinase function, we studied its effect on cyclin-dependent kinases (CDK) and cell cycle blockade in glioma cells. K252a blocked T98G cells at the G1/S and G2/M checkpoints. Consistent with cell cycle arrest, K252a was shown to hypophosphorylate Rb, upregulate p21, and decrease Cdc2 and Cdc25c activity. Finally, cell cycle arrest in T98G cells resulted in apoptosis as determined by cell morphology and DNA laddering. K252a is a useful tool for studying the effects of CDK inhibition and cell cycle blockade in tumor cells.
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Affiliation(s)
- L S Chin
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA.
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40
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Leone G, DeGregori J, Jakoi L, Cook JG, Nevins JR. Collaborative role of E2F transcriptional activity and G1 cyclindependent kinase activity in the induction of S phase. Proc Natl Acad Sci U S A 1999; 96:6626-31. [PMID: 10359762 PMCID: PMC21965 DOI: 10.1073/pnas.96.12.6626] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A considerable body of evidence points to a role for both cyclin E/cyclin-dependent kinase (cdk)2 activity and E2F transcription activity in the induction of S phase. We show that overexpression of cyclin E/cdk2 in quiescent cells induces S phase, that this coincides with an induction of E2F activity, and that coexpression of E2F enhances the cyclin E/cdk2-mediated induction of S phase. Likewise, E2F overexpression can induce S phase and does so in the apparent absence of cyclin E/cdk2 activity. In addition, although the inhibition of cyclin E/cdk2 activity blocks the induction of S phase after growth stimulation of normal mouse embryo fibroblasts, inhibition of cyclin E/cdk2 does not block S phase induction in Rb-/- cells where E2F activity is deregulated. These results point to the important roles for E2F and cyclin E/cdk2 in the induction of S phase. Moreover, the nature of the E2F targets and the suspected targets for cyclin E/cdk2 suggests a potential molecular mechanism for the collaborative action of cyclin E/cdk2 and E2F in the induction of S phase.
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Affiliation(s)
- G Leone
- Department of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
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41
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Abstract
Cyclins are regulatory subunits for cyclin dependent kinases in the coordination of the cell cycle. Cyclins can also serve non-cell cycle functions, such as the transactivation of estrogen receptor by cyclin D. Evidence for the participation of the G1 cyclins D and E in breast cancer is summarized, including transgenic and knockout mice, transfections, and expression patterns in cohort studies. Overexpression of cyclin D has been reported in ductal carcinoma in situ (DCIS), and similar overexpression of cyclin E is suggested. Strategies to reduce cyclin expression are discussed as potential prevention efforts.
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Affiliation(s)
- P S Steeg
- Women's Cancers Section, Laboratory of Pathology, Division of Clinical Sciences, National Cancer Institute, Bethesda, MD 20892, USA
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42
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Duncker BP, Pasero P, Braguglia D, Heun P, Weinreich M, Gasser SM. Cyclin B-cdk1 kinase stimulates ORC- and Cdc6-independent steps of semiconservative plasmid replication in yeast nuclear extracts. Mol Cell Biol 1999; 19:1226-41. [PMID: 9891057 PMCID: PMC116052 DOI: 10.1128/mcb.19.2.1226] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/1998] [Accepted: 10/26/1998] [Indexed: 11/20/2022] Open
Abstract
Nuclear extracts from Saccharomyces cerevisiae cells synchronized in S phase support the semiconservative replication of supercoiled plasmids in vitro. We examined the dependence of this reaction on the prereplicative complex that assembles at yeast origins and on S-phase kinases that trigger initiation in vivo. We found that replication in nuclear extracts initiates independently of the origin recognition complex (ORC), Cdc6p, and an autonomously replicating sequence (ARS) consensus. Nonetheless, quantitative density gradient analysis showed that S- and M-phase nuclear extracts consistently promote semiconservative DNA replication more efficiently than G1-phase extracts. The observed semiconservative replication is compromised in S-phase nuclear extracts deficient for the Cdk1 kinase (Cdc28p) but not in extracts deficient for the Cdc7p kinase. In a cdc4-1 G1-phase extract, which accumulates high levels of the specific Clb-Cdk1 inhibitor p40(SIC1), very low levels of semiconservative DNA replication were detected. Recombinant Clb5-Cdc28 restores replication in a cdc28-4 S-phase extract yet fails to do so in the cdc4-1 G1-phase extract. In contrast, the addition of recombinant Xenopus CycB-Cdc2, which is not sensitive to inhibition by p40(SIC1), restores efficient replication to both extracts. Our results suggest that in addition to its well-characterized role in regulating the origin-specific prereplication complex, the Clb-Cdk1 complex modulates the efficiency of the replication machinery itself.
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Affiliation(s)
- B P Duncker
- Swiss Institute for Experimental Cancer Research, CH-1066 Epalinges, Switzerland
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43
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Abstract
Biological scientists are eagerly confronting the challenge of understanding the regulatory mechanisms that control the cell division cycle in eukaryotes. New information will have major implications for the treatment of growth-related diseases and cancer in animals. In plants, cell division has a key role in root and shoot growth as well as in the development of vegetative storage organs and reproductive tissues such as flowers and seeds. Many of the strategies for crop improvement, especially those aimed at increasing yield, involve the manipulation of cell division. This review describes, in some detail, the current status of our understanding of the regulation of cell division in eukaryotes and especially in plants. It also features an outline of some preliminary attempts to exploit transgenesis for manipulation of plant cell division.
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Affiliation(s)
- M R Fowler
- Norman Borlaug Institute for Plant Science Research, De Montfort University, Scraptoft, Leicester, England
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44
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Schulman BA, Lindstrom DL, Harlow E. Substrate recruitment to cyclin-dependent kinase 2 by a multipurpose docking site on cyclin A. Proc Natl Acad Sci U S A 1998; 95:10453-8. [PMID: 9724724 PMCID: PMC27915 DOI: 10.1073/pnas.95.18.10453] [Citation(s) in RCA: 284] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/25/1998] [Indexed: 11/18/2022] Open
Abstract
An important question in the cell cycle field is how cyclin-dependent kinases (cdks) target their substrates. We have studied the role of a conserved hydrophobic patch on the surface of cyclin A in substrate recognition by cyclin A-cdk2. This hydrophobic patch is approximately 35A away from the active site of cdk2 and contains the MRAIL sequence conserved among a number of mammalian cyclins. In the x-ray structure of cyclin A-cdk2-p27, this hydrophobic patch contacts the RNLFG sequence in p27 that is common to a number of substrates and inhibitors of mammalian cdks. We find that mutation of this hydrophobic patch on cyclin A eliminates binding to proteins containing RXL motifs without affecting binding to cdk2. This docking site is critical for cyclin A-cdk2 phosphorylation of substrates containing RXL motifs, but not for phosphorylation of histone H1. Impaired substrate binding by the cyclin is the cause of the defect in RXL substrate phosphorylation, because phosphorylation can be rescued by restoring a cyclin A-substrate interaction in a heterologous manner. In addition, the conserved hydrophobic patch is important for cyclin A function in cells, contributing to cyclin A's ability to drive cells out of the G1 phase of the cell cycle. Thus, we define a mechanism by which cyclins can recruit substrates to cdks, and our results support the notion that a high local concentration of substrate provided by a protein-protein interaction distant from the active site is critical for phosphorylation by cdks.
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Affiliation(s)
- B A Schulman
- Massachusetts General Hospital Cancer Center, Building 149, 13th Street, Charlestown, MA 02129, USA
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45
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Dutta A. Regulation of S phase. Results Probl Cell Differ 1998; 22:35-55. [PMID: 9670318 DOI: 10.1007/978-3-540-69686-5_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- A Dutta
- Dept. of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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46
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Marheineke K, Krude T. Nucleosome assembly activity and intracellular localization of human CAF-1 changes during the cell division cycle. J Biol Chem 1998; 273:15279-86. [PMID: 9614144 DOI: 10.1074/jbc.273.24.15279] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We characterized changes of nucleosome assembly activity, intracellular localization, and reversible phosphorylation of the human chromatin assembly factor CAF-1 during the somatic cell division cycle. HeLa cells were synchronized in the G1, S, G2, and M phases of the cell cycle. All three subunits of human CAF-1 (p150, p60, and p48) are present during the entire cell cycle. In interphase, p150 and p60 are bound to the nucleus, but they predominantly dissociate from chromatin during mitosis. During S phase, p150 and p60 are concentrated at sites of intranuclear DNA replication. Only a fraction of total p48 is associated with p150 and p60, and the majority is present in other high molecular weight complexes. The other nucleosome assembly protein, NAP-1, is predominantly cytosolic throughout the cell cycle. Human CAF-1 efficiently mediates nucleosome assembly during complementary DNA strand synthesis in G1, S, and G2 phase cytosolic extracts. Active CAF-1 can be isolated as a 6.5 S complex from G1, S, and G2 phase nuclei. In contrast, CAF-1 isolated from mitotic cytosol does not support nucleosome assembly during DNA synthesis. In mitosis, the p60 subunit of inactive CAF-1 is hyperphosphorylated, whereas active CAF-1 in interphase contains hypophosphorylated and/or phosphorylated forms of p60.
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Affiliation(s)
- K Marheineke
- Wellcome/Cancer Research Campaign Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom and the Department of Zoology, University of Cambridge, United Kingdom
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47
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Garner-Hamrick PA, Fisher C. Antisense phosphorothioate oligonucleotides specifically down-regulate cdc25B causing S-phase delay and persistent antiproliferative effects. Int J Cancer 1998; 76:720-8. [PMID: 9610732 DOI: 10.1002/(sici)1097-0215(19980529)76:5<720::aid-ijc18>3.0.co;2-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cell cycle progression in mammalian cells is regulated by a family of cyclin-dependent kinases (cdks) that are activated by a family of 3 cdc25 phosphatases: cdc25A, cdc25B and cdc25C. We examined the expression of mRNA and protein of all 3 cdc25s during the HeLa cell cycle, and found that cdc25B protein has a unique and limited pattern of expression relative to other cdc25 homologs. Antisense oligonucleotides reduced cdc25B mRNA levels and dysregulated protein expression, while inhibiting S-phase progression in synchronized HeLa cells. Scrambled control oligonucleotides had no effect. Antisense oligonucleotides transfected in early G2-phase had no effect on cell cycle progression. A direct correlation between down-regulation of cdc25B and inhibition of thymidine incorporation was found using several oligonucleotides. Our results suggest a role for cdc25B in S-phase and demonstrate that inhibition of cdc25B has persistent antiproliferative effects.
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Affiliation(s)
- P A Garner-Hamrick
- Cell and Molecular Biology, Pharmacia and Upjohn, Inc., Kalamazoo, MI 49001, USA
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48
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Sauer K, Lehner CF. The role of cyclin E in the regulation of entry into S phase. PROGRESS IN CELL CYCLE RESEARCH 1998; 1:125-39. [PMID: 9552358 DOI: 10.1007/978-1-4615-1809-9_10] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cyclin E is a crucial regulator of entry into S phase in higher eukaryotes and acts in association with the protein kinase cdk2. Cyclin E expression is transcriptionally controlled in mammalian cells resulting in a maximum just before entry into S phase. Premature expression of cyclin E advances entry into S phase, while lack of cyclin E prevents entry into S phase. Cyclin E/cdk2 activity is regulated at multiple levels (by transcription, phosphorylation and inhibitor proteins) and appears to be involved in triggering initiation of DNA replication and in regulating genes important for proliferation and progression through S phase.
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Affiliation(s)
- K Sauer
- Friedrich-Miescher-Laboratorium der Max-Planck-Gesellschaft, Tübingen, Germany
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49
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Abstract
The cell cycle is driven by the sequential activation of a family of cyclin-dependent kinases (cdk), which phosphorylate and activate proteins that execute events critical to cell cycle progression. In mammalian cells cdk2-cyclin A has a role in S phase. Many replication proteins are potential substrates for this cdk kinase, suggesting that initiation, elongation and checkpoint control of replication could all be regulated by cdk2. The association of PCNA, a replication protein, with cdk-cyclins during G-1 to S phase transition and with cdk-cyclin inhibitors, adds an interesting complexity to regulation of DNA replication.
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Affiliation(s)
- R Fotedar
- Institut de Biologie Structurale J.-P. Ebel, Grenoble, France
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50
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Desdouets C, Sobczak-Thépot J, Murphy M, Bréchot C. Cyclin A: function and expression during cell proliferation. PROGRESS IN CELL CYCLE RESEARCH 1998; 1:115-23. [PMID: 9552357 DOI: 10.1007/978-1-4615-1809-9_9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cyclin A is a key regulatory protein which, in mammalian cells, is involved in both S phase and the G2/M transition of the cell cycle through its association with distinct cdks. Several lines of evidence have also implicated cyclin A in carcinogenesis. Our review concentrates on the role of cyclin A in S phase, in the S/G2 transition and in human carcinogenesis; it will also discuss the transcriptional regulation of cyclin A gene.
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