1051
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CHIP-Mediated Degradation and DNA Damage-Dependent Stabilization Regulate Base Excision Repair Proteins. Mol Cell 2008; 29:477-87. [DOI: 10.1016/j.molcel.2007.12.027] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 08/24/2007] [Accepted: 12/03/2007] [Indexed: 11/24/2022]
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1052
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Welcker M, Clurman BE. FBW7 ubiquitin ligase: a tumour suppressor at the crossroads of cell division, growth and differentiation. Nat Rev Cancer 2008; 8:83-93. [PMID: 18094723 DOI: 10.1038/nrc2290] [Citation(s) in RCA: 841] [Impact Index Per Article: 52.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
FBW7 (F-box and WD repeat domain-containing 7) is the substrate recognition component of an evolutionary conserved SCF (complex of SKP1, CUL1 and F-box protein)-type ubiquitin ligase. SCF(FBW7) degrades several proto-oncogenes that function in cellular growth and division pathways, including MYC, cyclin E, Notch and JUN. FBW7 is also a tumour suppressor, the regulatory network of which is perturbed in many human malignancies. Numerous cancer-associated mutations in FBW7 and its substrates have been identified, and loss of FBW7 function causes chromosomal instability and tumorigenesis. This Review focuses on structural and functional aspects of FBW7 and its role in the development of cancer.
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Affiliation(s)
- Markus Welcker
- Division of Human Biology, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, Washington 98109, USA.
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1053
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Rodier G, Coulombe P, Tanguay PL, Boutonnet C, Meloche S. Phosphorylation of Skp2 regulated by CDK2 and Cdc14B protects it from degradation by APC(Cdh1) in G1 phase. EMBO J 2008; 27:679-91. [PMID: 18239684 DOI: 10.1038/emboj.2008.6] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Accepted: 01/08/2008] [Indexed: 12/26/2022] Open
Abstract
The p27(Kip1) ubiquitin ligase receptor Skp2 is often overexpressed in human tumours and displays oncogenic properties. The activity of SCF(Skp2) is regulated by the APC(Cdh1), which targets Skp2 for degradation. Here we show that Skp2 phosphorylation on Ser64/Ser72 positively regulates its function in vivo. Phosphorylation of Ser64, and to a lesser extent Ser72, stabilizes Skp2 by interfering with its association with Cdh1, without affecting intrinsic ligase activity. Cyclin-dependent kinase (CDK)2-mediated phosphorylation of Skp2 on Ser64 allows its expression in mid-G1 phase, even in the presence of active APC(Cdh1). Reciprocally, dephosphorylation of Skp2 by the mitotic phosphatase Cdc14B at the M --> G1 transition promotes its degradation by APC(Cdh1). Importantly, lowering the levels of Cdc14B accelerates cell cycle progression from mitosis to S phase in an Skp2-dependent manner, demonstrating epistatic relationship of Cdc14B and Skp2 in the regulation of G1 length. Thus, our results reveal that reversible phosphorylation plays a key role in the timing of Skp2 expression in the cell cycle.
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Affiliation(s)
- Geneviève Rodier
- Institut de Recherche en Immunologie et Cancérologie, Université de Montréal, Montreal, Quebec, Canada
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1054
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Schmidt RL, Park CH, Ahmed AU, Gundelach JH, Reed NR, Cheng S, Knudsen BE, Tang AH. Inhibition of RAS-mediated transformation and tumorigenesis by targeting the downstream E3 ubiquitin ligase seven in absentia homologue. Cancer Res 2008; 67:11798-810. [PMID: 18089810 DOI: 10.1158/0008-5472.can-06-4471] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Constitutively active RAS small GTPases promote the genesis of human cancers. An important goal in cancer biology is to identify means of countervailing activated RAS signaling to reverse malignant transformation. Oncogenic K-RAS mutations are found in virtually all pancreatic adenocarcinomas, making the RAS pathway an ideal target for therapeutic intervention. How to best contravene hyperactivated RAS signaling has remained elusive in human pancreatic cancers. Guided by the Drosophila studies, we reasoned that a downstream mediator of RAS signals might be a suitable anti-RAS target. The E3 ubiquitin ligase seven in absentia (SINA) is an essential downstream component of the Drosophila RAS signal transduction pathway. Thus, we determined the roles of the conserved human homologues of SINA, SIAHs, in mammalian RAS signaling and RAS-mediated tumorigenesis. We report that similar to its Drosophila counterpart, human SIAH is also required for oncogenic RAS signaling in pancreatic cancer. Inhibiting SIAH-dependent proteolysis blocked RAS-mediated focus formation in fibroblasts and abolished the tumor growth of human pancreatic cancer cells in soft agar as well as in athymic nude mice. Given the high level of conservation of RAS and SIAH function, our study provides useful insights into altered proteolysis in the RAS pathway in tumor initiation, progression, and oncogenesis. By targeting SIAH, we have found a novel means to contravene oncogenic RAS signaling and block RAS-mediated transformation/tumorigenesis. Thus, SIAH may offer a novel therapeutic target to halt tumor growth and ameliorate RAS-mediated pancreatic cancer.
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Affiliation(s)
- Rebecca L Schmidt
- Department of Biochemistry and Molecular Biology, Mayo Clinic Cancer Center, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
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1055
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Liu W, Li W, Fujita T, Yang Q, Wan Y. Proteolysis of CDH1 enhances susceptibility to UV radiation-induced apoptosis. Carcinogenesis 2008; 29:263-72. [PMID: 18174259 DOI: 10.1093/carcin/bgm251] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
As a critical ubiquitin ligase, the anaphase-promoting complex/cyclosome (APC/C) governs cell cycle progression, signaling modulation and the pathogenesis of some human diseases. Recent studies implicate APC in maintaining genomic integrity, but the mechanism by which it plays such a role remains largely unknown. We report here that acute UV radiation triggers proteolysis of CDH1, an activator of APC, which is involved in regulation of apoptosis induced by UV radiation. Depletion of CDH1 by RNA interference enhances the cellular susceptibility to apoptosis in response to UV radiation, whereas overexpression of non-degradable CDH1 delays UV radiation-induced apoptosis. In addition, UV-induced degradation of CDH1 results in the accumulation of cyclin B1 and therefore to increased CDK1 activity, which is believed to enhance UV-induced apoptosis. The present results unveil a novel role for the APC in UV-induced cell death and demonstrate a new regulatory mechanism for APC/CDH1 through proteolysis.
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Affiliation(s)
- Weijun Liu
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine and University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213-1863, USA
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1056
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Salon C, Brambilla E, Brambilla C, Lantuejoul S, Gazzeri S, Eymin B. Altered pattern of Cul-1 protein expression and neddylation in human lung tumours: relationships with CAND1 and cyclin E protein levels. J Pathol 2007; 213:303-10. [PMID: 17823919 DOI: 10.1002/path.2223] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The Cul-1 protein is the scaffold element of SCF complexes that are involved in the proteasomal degradation of numerous proteins regulating cell cycle progression. Owing to this central role in cell growth control, aberrant expression of the components of SCF is thought to play a role during tumourigenesis. Nothing is known about Cul-1 expression in human tumours. In this study, we have analysed its status in a series of 128 human lung carcinomas, comprising 50 non-small cell lung cancers (NSCLCs; 29 squamous cell carcinomas and 21 adenocarcinomas) and 78 neuroendocrine (NE) lung tumours (24 typical and atypical carcinoids, 19 large cell NE carcinomas and 35 small cell lung carcinomas), using immunohistochemistry. We report for the first time an altered pattern of Cul-1 expression in human tumours; indeed, we show that Cul-1 expression is up-regulated in 40% (51/128) of all lung tumours as compared to normal lung tissues, including 34% (17/50), 75% (18/24) and 30% (16/54) of NSCLCs, carcinoids and high grade neuroendocrine lung carcinomas, respectively. Furthermore, we demonstrate that high levels of Cul-1 protein are associated with a low KI67 proliferative index (p = 0.005) and with a decrease in the cyclin E oncoprotein (p = 0.0003), one of the major targets of SCF complexes. These data suggest that up-regulation of Cul-1 could protect cells from hyperproliferative signals through cyclin E down-regulation. Cul-1 is modified by neddylation, a post-translational modification that grafts ubiquitin-like Nedd8/Rub1 residues and controls Cul-1 activity. We also provide evidence that neddylated forms of Cul-1 are specifically expressed in high-grade NE lung tumours and are associated with down-regulation of the Cul-1 inhibitor CAND1 (p = 0.03) and a high level of cyclin E (p = 0.0002). These data support the notion that alterations in the Cul-1 neddylation/deneddylation pathway could contribute to the development of these highly aggressive lung tumours.
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Affiliation(s)
- C Salon
- Equipe Bases Moléculaires de la Progression des Cancers du Poumon, Centre de Recherche INSERM U823, Institut Albert Bonniot, 38706 La Tronche Cedex, France
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1057
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Arama E, Bader M, Rieckhof GE, Steller H. A ubiquitin ligase complex regulates caspase activation during sperm differentiation in Drosophila. PLoS Biol 2007; 5:e251. [PMID: 17880263 PMCID: PMC1976628 DOI: 10.1371/journal.pbio.0050251] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 07/25/2007] [Indexed: 11/19/2022] Open
Abstract
In both insects and mammals, spermatids eliminate their bulk cytoplasm as they undergo terminal differentiation. In Drosophila, this process of dramatic cellular remodeling requires apoptotic proteins, including caspases. To gain further insight into the regulation of caspases, we screened a large collection of sterile male flies for mutants that block effector caspase activation at the onset of spermatid individualization. Here, we describe the identification and characterization of a testis-specific, Cullin-3-dependent ubiquitin ligase complex that is required for caspase activation in spermatids. Mutations in either a testis-specific isoform of Cullin-3 (Cul3(Testis)), the small RING protein Roc1b, or a Drosophila orthologue of the mammalian BTB-Kelch protein Klhl10 all reduce or eliminate effector caspase activation in spermatids. Importantly, all three genes encode proteins that can physically interact to form a ubiquitin ligase complex. Roc1b binds to the catalytic core of Cullin-3, and Klhl10 binds specifically to a unique testis-specific N-terminal Cullin-3 (TeNC) domain of Cul3(Testis) that is required for activation of effector caspase in spermatids. Finally, the BIR domain region of the giant inhibitor of apoptosis-like protein dBruce is sufficient to bind to Klhl10, which is consistent with the idea that dBruce is a substrate for the Cullin-3-based E3-ligase complex. These findings reveal a novel role of Cullin-based ubiquitin ligases in caspase regulation.
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Affiliation(s)
- Eli Arama
- Strang Laboratory of Cancer Research, The Rockefeller University, New York, New York, United States of America
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
| | - Maya Bader
- Strang Laboratory of Cancer Research, The Rockefeller University, New York, New York, United States of America
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
| | - Gabrielle E Rieckhof
- Strang Laboratory of Cancer Research, The Rockefeller University, New York, New York, United States of America
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
| | - Hermann Steller
- Strang Laboratory of Cancer Research, The Rockefeller University, New York, New York, United States of America
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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1058
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Gu Q, Bowden GT, Normolle D, Sun Y. SAG/ROC2 E3 ligase regulates skin carcinogenesis by stage-dependent targeting of c-Jun/AP1 and IkappaB-alpha/NF-kappaB. ACTA ACUST UNITED AC 2007; 178:1009-23. [PMID: 17846172 PMCID: PMC2064624 DOI: 10.1083/jcb.200612067] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Sensitive to apoptosis gene (SAG)/regulator of cullins-2-Skp1-cullin-F-box protein (SCF) E3 ubiquitin ligase regulates cellular functions through ubiquitination and degradation of protein substrates. We report that, when expressed in mouse epidermis driven by the K14 promoter, SAG inhibited TPA-induced c-Jun levels and activator protein-1 (AP-1) activity in both in vitro primary culture, in vivo transgenic mice, and an AP-1- luciferase reporter mouse model. After AP-1 inactivation, epidermal proliferation induced by 7,12-dimethylbenz(a)-anthracene/12-O-tetradecanoylphorbol-13-acetate at the early stage of carcinogenesis was substantially inhibited. Later stage tumor formation was also substantially inhibited with prolonged latency and reduced frequency of tumor formation. Interestingly, SAG expression increased tumor size, not because of accelerated proliferation, but caused by reduced apoptosis resulting, at least in part, from nuclear factor kappaB (NF-kappaB) activation. Thus, SAG, in a manner depending on the availability of F-box proteins, demonstrated early-stage suppression of tumor formation by promoting c-Jun degradation, thereby inhibiting AP-1, and later-stage enhancement of tumor growth, by promoting inhibitor of kappaBalpha degradation to activate NF-kappaB and inhibit apoptosis.
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Affiliation(s)
- Qingyang Gu
- Department of Radiation Oncology, University of Michigan Comprehensive Cancer Center, Ann Arbor, MI 48109, USA
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1059
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Liu H, Cheng EHY, Hsieh JJD. Bimodal degradation of MLL by SCFSkp2 and APCCdc20 assures cell cycle execution: a critical regulatory circuit lost in leukemogenic MLL fusions. Genes Dev 2007; 21:2385-98. [PMID: 17908926 PMCID: PMC1993870 DOI: 10.1101/gad.1574507] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human chromosome 11q23 translocations disrupting MLL result in poor prognostic leukemias. It fuses the common MLL N-terminal approximately 1400 amino acids in-frame with >60 different partners without shared characteristics. In addition to the well-characterized activity of MLL in maintaining Hox gene expression, our recent studies established an MLL-E2F axis in orchestrating core cell cycle gene expression including Cyclins. Here, we demonstrate a biphasic expression of MLL conferred by defined windows of degradation mediated by specialized cell cycle E3 ligases. Specifically, SCF(Skp2) and APC(Cdc20) mark MLL for degradation at S phase and late M phase, respectively. Abolished peak expression of MLL incurs corresponding defects in G1/S transition and M-phase progression. Conversely, overexpression of MLL blocks S-phase progression. Remarkably, MLL degradation initiates at its N-terminal approximately 1400 amino acids, and tested prevalent MLL fusions are resistant to degradation. Thus, impaired degradation of MLL fusions likely constitutes the universal mechanism underlying all MLL leukemias. Our data conclude an essential post-translational regulation of MLL by the cell cycle ubiquitin/proteasome system (UPS) assures the temporal necessity of MLL in coordinating cell cycle progression.
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Affiliation(s)
- Han Liu
- Molecular Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Emily H.-Y. Cheng
- Molecular Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - James J.-D. Hsieh
- Molecular Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Corresponding author.E-MAIL ; FAX (314) 362-1589
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1060
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Luke-Glaser S, Pintard L, Tyers M, Peter M. The AAA-ATPase FIGL-1 controls mitotic progression, and its levels are regulated by the CUL-3MEL-26 E3 ligase in the C. elegans germ line. J Cell Sci 2007; 120:3179-87. [PMID: 17878235 DOI: 10.1242/jcs.015883] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Members of the AAA-ATPase (ATPases associated with diverse cellular activities) family use the energy from ATP hydrolysis to disrupt protein complexes involved in many cellular processes. Here, we report that FIGL-1 (Fidgetin-like 1), the single Caenorhabditis elegans homolog of mammalian fidgetin and fidgetin-like 1 AAA-ATPases, controls progression through mitosis in the germ line and the early embryo. Loss of figl-1 function leads to the accumulation of mitotic nuclei in the proliferative zone of the germ line, resulting in sterility owing to depletion of germ cells. Like the AAA-ATPase MEI-1 (also known as katanin), FIGL-1 interacts with microtubules and with MEL-26, a specificity factor of CUL-3-based E3 ligases involved in targeting proteins for ubiquitin-dependent degradation by the 26S proteasome. In the germ line, FIGL-1 is enriched in nuclei of mitotic cells, but it disappears at the transition into meiosis. Conversely, MEL-26 expression is low in nuclei of the mitotic zone and induced during meiosis. FIGL-1 accumulates in the germ line and spreads to the meiotic zone after inactivation of mel-26 or cul-3 in vivo. We conclude that degradation of FIGL-1 by the CUL-3MEL-26 E3 ligase spatially restricts FIGL-1 function to mitotic cells, where it is required for correct progression through mitosis.
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Affiliation(s)
- Sarah Luke-Glaser
- Institute of Biochemistry, HPM G8, ETH Hönggerberg, 8093 Zürich, Switzerland
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1061
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Onoyama I, Tsunematsu R, Matsumoto A, Kimura T, de Alborán IM, Nakayama K, Nakayama KI. Conditional inactivation of Fbxw7 impairs cell-cycle exit during T cell differentiation and results in lymphomatogenesis. ACTA ACUST UNITED AC 2007; 204:2875-88. [PMID: 17984302 PMCID: PMC2118521 DOI: 10.1084/jem.20062299] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Cell proliferation is strictly controlled during differentiation. In T cell development, the cell cycle is normally arrested at the CD4+CD8+ stage, but the mechanism underlying such differentiation-specific exit from the cell cycle has been unclear. Fbxw7 (also known as Fbw7, Sel-10, hCdc4, or hAgo), an F-box protein subunit of an SCF-type ubiquitin ligase complex, induces the degradation of positive regulators of the cell cycle, such as c-Myc, c-Jun, cyclin E, and Notch. FBXW7 is often mutated in a subset of human cancers. We have now achieved conditional inactivation of Fbxw7 in the T cell lineage of mice and found that the cell cycle is not arrested at the CD4+CD8+ stage in the homozygous mutant animals. The mutant mice manifested thymic hyperplasia as a result of c-Myc accumulation and eventually developed thymic lymphoma. In contrast, mature T cells of the mutant mice failed to proliferate in response to mitogenic stimulation and underwent apoptosis in association with accumulation of c-Myc and p53. These latter abnormalities were corrected by deletion of p53. Our results suggest that Fbxw7 regulates the cell cycle in a differentiation-dependent manner, with its loss resulting in c-Myc accumulation that leads to hyperproliferation in immature T cells but to p53-dependent cell-cycle arrest and apoptosis in mature T cells.
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Affiliation(s)
- Ichiro Onoyama
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan
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1062
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Pollok S, Grosse F. Cdc45 degradation during differentiation and apoptosis. Biochem Biophys Res Commun 2007; 362:910-5. [PMID: 17767920 DOI: 10.1016/j.bbrc.2007.08.069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 08/14/2007] [Indexed: 11/29/2022]
Abstract
Cell division cycle protein 45 (Cdc45) is crucial for the initiation as well as the elongation process of eukaryotic DNA replication. Our findings suggested that the Cdc45 protein is ubiquitylated and degraded by the proteasome pathway in human cells. Firstly, the fate of Cdc45 protein after induction of terminal differentiation of cultured human cells was significantly decelerated by application of proteasomal inhibitors. Secondly, we identified various putative destruction boxes and one KEN-box in the amino acid sequence of vertebrate Cdc45, which indicate that Cdc45 seems to be a novel substrate of the anaphase promoting complex/cyclosome. Thus, the evidences for ubiquitylation of Cdc45 refer the first posttranslational modification of this essential replication factor. We also found, that the human Cdc45 protein was not cleaved during apoptosis of cultured cells. This is in accordance with reports demonstrating the absence of indiscriminative cleavage of replication proteins during the programmed cell death.
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Affiliation(s)
- S Pollok
- Leibniz Institute for Age Research (Fritz Lipmann Institute), Biochemistry Group, Jena, Germany
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1063
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Kuboniwa M, Hasegawa Y, Mao S, Shizukuishi S, Amano A, Lamont RJ, Yilmaz O. P. gingivalis accelerates gingival epithelial cell progression through the cell cycle. Microbes Infect 2007; 10:122-8. [PMID: 18280195 DOI: 10.1016/j.micinf.2007.10.011] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 10/16/2007] [Accepted: 10/17/2007] [Indexed: 01/12/2023]
Abstract
P. gingivalis, an opportunistic pathogen in periodontal disease, can reside within the epithelial cells that line the gingival crevice. A proteomic analysis revealed that infection of gingival epithelial cells with P. gingivalis induces broadly based changes in the level and phosphorylation status of proteins that exert multi-level control on the eukaryotic cell cycle. Pathways that were impacted by P. gingivalis included those involving cyclins, p53 and PI3K. The predicted infection-dependent phenotype was confirmed by cytofluorimetry that showed an enhanced proliferation rate of gingival epithelial cells infected with P. gingivalis associated with accelerated progression through the S-phase. Elevated cell proliferation was dependent on the presence of the long fimbriae of P. gingivalis. The ability of P. gingivalis, a common inhabitant of the subgingival crevice, to accelerate cell cycling could have biological consequences for barrier and signaling functions, and for physiological status, of the gingival epithelium.
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Affiliation(s)
- Masae Kuboniwa
- Department of Preventive Dentistry, Osaka University Graduate School of Dentistry, Osaka, Japan
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1064
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Sala SG, Muñoz U, Bartolomé F, Bermejo F, Martín-Requero A. HMG-CoA reductase inhibitor simvastatin inhibits cell cycle progression at the G1/S checkpoint in immortalized lymphocytes from Alzheimer's disease patients independently of cholesterol-lowering effects. J Pharmacol Exp Ther 2007; 324:352-9. [PMID: 17928568 DOI: 10.1124/jpet.107.128959] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Recent work has suggested that statins may exert beneficial effects on patients suffering from Alzheimer's disease (AD). The pharmacological effects of statins extend beyond their cholesterol-lowering properties. Based on the antineoplastic and apoptotic effects of statins in several cell types, we hypothesized that statins may be able to protect neurons by controlling the regulation of cell cycle. A growing body of evidence indicates that neurodegeneration involves the activation of cell cycle machinery in postmitotic neurons. We and others have presented direct evidence to support the hypothesis that the failure of cell cycle control is not restricted to neurons in AD patients, but that it occurs in peripheral cells as well. For these reasons, we found it worthy to study the role of simvastatin on cell proliferation in immortalized lymphocytes from AD patients. We report here that simvastatin (SIM) inhibits the serum-mediated enhancement of cell proliferation in AD by blocking the events critical for G(1)/S transition. SIM induces a partial blockade of retinoblastoma protein phosphorylation and inhibition of cyclin E/cyclin-dependent kinase (CDK)2 activity associated with increased levels of the CDK inhibitors p21(Cip1) and p27(kip1). These effects of SIM on AD lymphoblasts are dependent on inhibition of the proteasome-mediated degradation of p21 and p27 proteins. The antiproliferative effect of this natural statin may provide a therapeutic approach for AD disease.
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Affiliation(s)
- Simone G Sala
- Centro de Investigaciones Biológicas, Ramiro de Maeztu 9, 28040 Madrid, Spain
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1065
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Mtango NR, Latham KE. Ubiquitin proteasome pathway gene expression varies in rhesus monkey oocytes and embryos of different developmental potential. Physiol Genomics 2007; 31:1-14. [PMID: 17550997 DOI: 10.1152/physiolgenomics.00040.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Protein degradation via the ubiquitin-proteasome pathway (UPP) plays a key role in diverse aspects of cell physiology and development. In the early embryo, the UPP may play an important role in the transition from maternal to embryonic control of development. Disruptions in the UPP could thus compromise embryo developmental potential. Additionally, species-specific requirements may dictate diverse patterns of regulation of the UPP components. To investigate the expression of UPP components in a nonhuman primate embryo model, to compare expression between a primate and nonprimate species, and to determine whether disruption of this pathway may contribute to reduced developmental potential, we examined the expression of >50 mRNAs encoding UPP components in rhesus monkey oocytes and embryos. We compared this expression between the rhesus monkey and mouse embryo and between rhesus monkey oocytes and embryos of high, intermediate, and low developmental potential. We report here the temporal patterns of UPP gene expression in oocytes and during preimplantation development, including striking differences between the rhesus monkey and mouse. We also report significant differences in UPP gene expression correlating with oocyte and embryo developmental competence and associated with altered regulation of maternally inherited mRNAs encoding these proteins.
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Affiliation(s)
- Namdori R Mtango
- The Fels Institute for Cancer Research and Molecular Biology, Temple University, Philadelphia, Pennsylvania, USA
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1066
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Chen WY, Weng JH, Huang CC, Chung BC. Histone deacetylase inhibitors reduce steroidogenesis through SCF-mediated ubiquitination and degradation of steroidogenic factor 1 (NR5A1). Mol Cell Biol 2007; 27:7284-90. [PMID: 17709382 PMCID: PMC2168912 DOI: 10.1128/mcb.00476-07] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Histone deacetylase (HDAC) inhibitors such as trichostatin A and valproic acid modulate transcription of many genes by inhibiting the activities of HDACs, resulting in the remodeling of chromatin. Yet this effect is not universal for all genes. Here we show that HDAC inhibitors suppressed the expression of steroidogenic gene CYP11A1 and decreased steroid secretion by increasing the ubiquitination and degradation of SF-1, a factor important for the transcription of all steroidogenic genes. This was accompanied by increased expression of Ube2D1 and SKP1A, an E2 ubiquitin conjugase and a subunit of the E3 ubiquitin ligase in the Skp1/Cul1/F-box protein (SCF) family, respectively. Reducing SKP1A expression with small interfering RNA resulted in recovery of SF-1 levels, demonstrating that the activity of SCF E3 ubiquitin ligase is required for the SF-1 degradation induced by HDAC inhibitors. Overexpression of exogenous SF-1 restored steroidogenic activities even in the presence of HDAC inhibitors. Thus, increased SF-1 degradation is the cause of the reduction in steroidogenesis caused by HDAC inhibitors. The increased SKP1A expression and SCF-mediated protein degradation could be the mechanism underlying the mode of action of HDAC inhibitors.
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Affiliation(s)
- Wei-Yi Chen
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan
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1067
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Abstract
Irreversible covalent inhibitors equipped with reporter groups, also termed activity-based probes, allow the study of target enzymes based on catalytic activity instead of expression level, which does not necessarily indicate protein function and subsequent cellular consequences. Activity-based probes offer advantages over traditional techniques: they can be applied to the cell or tissue of choice and molecular imaging and pharmacology applications are possible. Here the design and use of probes directed at enzymatic activities in the ubiquitin proteasome system are discussed. This system holds promise for the development of new, targeted anticancer therapies and the probes discussed here might aid in fulfilling this promise.
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Affiliation(s)
- Huib Ovaa
- Division of Cellular Biochemistry, Netherlands Cancer Institute (NKI), Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
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1068
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Fingerle-Rowson G, Petrenko O. MIF coordinates the cell cycle with DNA damage checkpoints. Lessons from knockout mouse models. Cell Div 2007; 2:22. [PMID: 17640378 PMCID: PMC1941730 DOI: 10.1186/1747-1028-2-22] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Accepted: 07/19/2007] [Indexed: 12/22/2022] Open
Abstract
Macrophage migration inhibitory factor (MIF) is a ubiquitously expressed pro-inflammatory mediator that has also been implicated in the process of oncogenic transformation and tumor progression. We used a genetic approach to show that deletion of the MIF gene in mice has several major consequences for the proliferative and transforming properties of cells. MIF-deficient cells exhibit increased resistance to oncogenic transformation. The transformation defects associated with MIF deficiency can be overcome through concomitant inactivation of the p53 and Rb/E2F tumor suppressor pathways. We have produced compelling evidence that the effects of MIF on cell survival and tumorigenesis are mediated through overlapping pathways, wherein MIF and p53 functionally antagonize each other in the cell. However, the involvement of MIF in p53 function is secondary to p53-independent mechanisms controlling protein stability, DNA damage checkpoints, and the integrity of the genome. Given the broad spectrum of cell types that normally express MIF and its elevated levels at sites of chronic inflammation, this pathway may be generic for many early stage tumors.
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Affiliation(s)
- Günter Fingerle-Rowson
- University Hospital Cologne, Clinic I of Internal Medicine, Dept. of Hematology and Oncology, LFI, Level 4, Room 704, Kerpenerstr. 62, 50924 Cologne, Germany
| | - Oleksi Petrenko
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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1069
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Ferguson JE, Wu Y, Smith K, Charles P, Powers K, Wang H, Patterson C. ASB4 is a hydroxylation substrate of FIH and promotes vascular differentiation via an oxygen-dependent mechanism. Mol Cell Biol 2007; 27:6407-19. [PMID: 17636018 PMCID: PMC2099627 DOI: 10.1128/mcb.00511-07] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The molecular mechanisms of endothelial differentiation into a functional vascular network are incompletely understood. To identify novel factors in endothelial development, we used a microarray screen with differentiating embryonic stem (ES) cells that identified the gene for ankyrin repeat and SOCS box protein 4 (ASB4) as the most highly differentially expressed gene in the vascular lineage during early differentiation. Like other SOCS box-containing proteins, ASB4 is the substrate recognition molecule of an elongin B/elongin C/cullin/Roc ubiquitin ligase complex that mediates the ubiquitination and degradation of substrate protein(s). High levels of ASB4 expression in the embryonic vasculature coincide with drastic increases in oxygen tension as placental blood flow is initiated. However, as vessels mature and oxygen levels stabilize, ASB4 expression is quickly downregulated, suggesting that ASB4 may function to modulate an endothelium-specific response to increasing oxygen tension. Consistent with the hypothesis that ASB4 function is regulated by oxygen concentration, ASB4 interacts with the factor inhibiting HIF1alpha (FIH) and is a substrate for FIH-mediated hydroxylation via an oxygen-dependent mechanism. Additionally, overexpression of ASB4 in ES cells promotes differentiation into the vascular lineage in an oxygen-dependent manner. We postulate that hydroxylation of ASB4 in normoxia promotes binding to and degradation of substrate protein(s) to modulate vascular differentiation.
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Affiliation(s)
- James E Ferguson
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, USA
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1070
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Bai S, Datta J, Jacob ST, Ghoshal K. Treatment of PC12 cells with nerve growth factor induces proteasomal degradation of T-cadherin that requires tyrosine phosphorylation of its cadherin domain. J Biol Chem 2007; 282:27171-27180. [PMID: 17631504 PMCID: PMC2243237 DOI: 10.1074/jbc.m700691200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
T-cadherin (T-Cad), a unique member of the cadherin family of proteins, plays an important role in cell adhesion and cell signaling. Recently, we demonstrated that T-Cad is transcriptionally repressed by DNA methyltransferase 3b during nerve growth factor (NGF)-induced neuronal differentiation of PC12 cells. Here, we show that T-Cad expression is also regulated at the post-translational level by the proteasomal pathway in these cells, which is facilitated upon NGF treatment. Pulse-chase experiments demonstrated that NGF treatment significantly reduced the half-life of T-Cad. Degradation of T-Cad was blocked upon treatment of PC12 cells with the proteasomal inhibitor ZLLL or lactacystin. Ectopic expression of Cdh1 (CDC20 homolog 1), one of the substrate recognition components of anaphase promoting complex (E3 ligase), stimulated T-Cad degradation. Deletion of CD1, one of the five extracellular cadherin domains (CD), promoted degradation of T-Cad, especially in the presence of NGF. On the contrary, deletion of CD2 stabilized this protein maximally. Ubiquitination of different deletion mutants indicates that T-Cad harbors multiple ubiquitination signals. Furthermore, genistein, a protein-tyrosine kinase inhibitor, impeded T-Cad degradation in PC12 cells, implicating requirement of tyrosine phosphorylation in this process. Mutation at tyrosine 327 (Y327F) markedly increased the half-life of T-Cad, suggesting that phosphorylation of this tyrosine residue located within CD2 is critical for this process. These results show that T-cadherin is subject to dual regulation during NGF-induced differentiation of PC12 cells, namely transcriptional repression mediated by Dnmt3b and post-translational degradation through the proteasomal pathway. These data, together with the inhibitory role of T-Cad in neurite outgrowth of PC12 cells upon NGF treatment, underscore the significance of its stringent regulation during this differentiation process.
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Affiliation(s)
- Shoumei Bai
- Department of Molecular and Cellular Biochemistry, College of Medicine, and the
| | - Jharna Datta
- Department of Molecular and Cellular Biochemistry, College of Medicine, and the
| | - Samson T Jacob
- Department of Molecular and Cellular Biochemistry, College of Medicine, and the; Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210.
| | - Kalpana Ghoshal
- Department of Molecular and Cellular Biochemistry, College of Medicine, and the
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1071
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Ding M, Chao D, Wang G, Shen K. Spatial regulation of an E3 ubiquitin ligase directs selective synapse elimination. Science 2007; 317:947-51. [PMID: 17626846 DOI: 10.1126/science.1145727] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Stereotyped synaptic connectivity can arise both by precise recognition between appropriate partners during synaptogenesis and by selective synapse elimination. The molecular mechanisms that underlie selective synapse removal are largely unknown. We found that stereotyped developmental elimination of synapses in the Caenorhabditis elegans hermaphrodite-specific motor neuron (HSNL) was mediated by an E3 ubiquitin ligase, a Skp1-cullin-F-box (SCF) complex composed of SKR-1 and the F-box protein SEL-10. SYG-1, a synaptic adhesion molecule, bound to SKR-1 and inhibited assembly of the SCF complex, thereby protecting nearby synapses. Thus, subcellular regulation of ubiquitin-mediated protein degradation contributes to precise synaptic connectivity through selective synapse elimination.
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Affiliation(s)
- Mei Ding
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA
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1072
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Zhang N, Liu J, Ding X, Aikhionbare F, Jin C, Yao X. FBXL5 interacts with p150Glued and regulates its ubiquitination. Biochem Biophys Res Commun 2007; 359:34-9. [PMID: 17532294 DOI: 10.1016/j.bbrc.2007.05.068] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2007] [Accepted: 05/07/2007] [Indexed: 11/15/2022]
Abstract
The microtubule motor cytoplasmic dynein and its activator dynactin drive vesicular transport and mitotic spindle organization. p150(Glued) is the dynactin subunit responsible for binding to dynein and microtubules. The F-box proteins constitute one of the four subunits of ubiquitin protein ligase complex called SCFs (SKP1-cullin-F-box), which governs phosphorylation-dependent ubiquitination and subsequent proteolysis. Our recent study showed that the proteolysis of mitotic kinesin CENP-E is mediated by SCF via a direct Skp1 link [D. Liu, N. Zhang, J. Du, X. Cai, M. Zhu, C. Jin, Z. Dou, C. Feng, Y. Yang, L. Liu, K. Takeyasu, W. Xie, X. Yao, Interaction of Skp1 with CENP-E at the midbody is essential for cytokinesis, Biochem. Biophys. Res. Commun. 345 (2006) 394-402]. Here we show that F-box protein FBXL5 interacts with p150(Glued) and orchestrates its turnover via ubiquitination. FBXL5 binds to p150(Glued)in vitro and in vivo. FBXL5 and p150(Glued) co-localize primarily in the cytoplasm with peri-nuclear enrichment in HeLa cells. Overexpression of FBXL5 promotes poly-ubiquitination of p150(Glued) and protein turnover of p150(Glued). Our findings provide a potential mechanism by which p150(Glued) protein function is regulated by SCFs.
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Affiliation(s)
- Ning Zhang
- Division of Cellular Dynamics, Hefei National Laboratory for Physical Sciences and Chinese University of Science & Technology, Hefei 230027, China
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1073
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Susaki E, Nakayama K, Nakayama KI. Cyclin D2 translocates p27 out of the nucleus and promotes its degradation at the G0-G1 transition. Mol Cell Biol 2007; 27:4626-40. [PMID: 17452458 PMCID: PMC1951473 DOI: 10.1128/mcb.00862-06] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 06/15/2006] [Accepted: 04/10/2007] [Indexed: 01/12/2023] Open
Abstract
The nuclear export and cytoplasmic degradation of the cyclin-dependent kinase inhibitor p27 are required for effective progression of the cell cycle through the G(0)-G(1) transition. The mechanism responsible for this translocation of p27 has remained unclear, however. We now show that cyclin D2 directly links growth signaling with the nuclear export of p27 at the G(0)-G(1) transition in some cell types. The up-regulation of cyclin D2 in response to mitogenic stimulation was found to occur earlier than that of other D-type cyclins and in parallel with down-regulation of p27 at the G(0)-G(1) transition. RNA interference-mediated depletion of cyclin D2 inhibited the nuclear export of p27 and delayed its degradation at the G(0)-G(1) transition. In contrast, overexpression of cyclin D2 in G(0) phase shifted the localization of p27 from the nucleus to the cytoplasm and reduced the stability of p27. Overexpression of the cyclin D2(T280A) mutant, whose export from the nucleus is impaired, prevented the translocation and degradation of p27. These results indicate that cyclin D2 translocates p27 from the nucleus into the cytoplasm for its KPC-dependent degradation at the G(0)-G(1) transition.
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Affiliation(s)
- Etsuo Susaki
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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1074
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Reichert M, Saur D, Hamacher R, Schmid RM, Schneider G. Phosphoinositide-3-kinase signaling controls S-phase kinase-associated protein 2 transcription via E2F1 in pancreatic ductal adenocarcinoma cells. Cancer Res 2007; 67:4149-56. [PMID: 17483325 DOI: 10.1158/0008-5472.can-06-4484] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The phosphoinositide-3-kinase (PI3K)/AKT signaling pathway controls fundamental processes of cancer cell biology like proliferation and cell survival. The PI3K/AKT pathway is activated in pancreatic ductal adenocarcinoma (PDAC) cells. The molecular mechanisms linking PI3K signaling to the cell cycle machinery in PDAC cells are not investigated in detail. Using the PI3K inhibitor Ly294002 as well as small interfering RNA targeting AKT1 expression, we show that PI3K controls the proliferation and G(1) phase progression of PDAC cells. Gene profiling revealed several important regulators of G(1)-S phase progression controlled by PI3K signaling like p21(Cip1), S-phase kinase-associated protein 2 (SKP2), CDC25a, cyclin A, cyclin D2, CDK2, and cyclin E. We show that the F-box protein SKP2, an oncogene up-regulated in PDAC, is transcriptionally regulated by the PI3K/AKT1 pathway in PDAC cells. At the molecular level, the control of the SKP2 gene by PI3K is due to the regulation of E2F1 binding to the proximal SKP2 gene promoter. The complex and profound connection of PI3K/AKT1 signaling to the cell cycle qualifies this pathway as a suitable target for therapeutic intervention in PDAC.
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Affiliation(s)
- Maximilian Reichert
- Department of Internal Medicine, Technical University of Munich, Munich, Germany
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1075
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Wei S, Lin LF, Yang CC, Wang YC, Chang GD, Chen H, Chen CS. Thiazolidinediones modulate the expression of beta-catenin and other cell-cycle regulatory proteins by targeting the F-box proteins of Skp1-Cul1-F-box protein E3 ubiquitin ligase independently of peroxisome proliferator-activated receptor gamma. Mol Pharmacol 2007; 72:725-33. [PMID: 17569795 DOI: 10.1124/mol.107.035287] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Considering the role of aberrant beta-catenin signaling in tumorigenesis, we investigated the mechanism by which the peroxisome proliferator-activated receptor gamma (PPARgamma) agonist troglitazone facilitated beta-catenin down-regulation. We demonstrate that troglitazone and its more potent PPARgamma-inactive analogs Delta2TG and STG28 mediated the proteasomal degradation of beta-catenin in prostate cancer cells by up-regulating the expression of beta-transducin repeat-containing protein (beta-TrCP), an F-box component of the Skp1-Cul1-F-box protein E3 ubiquitin ligase. Evidence indicates that although small interfering RNA-mediated beta-TrCP knockdown protected cells against STG28-facilitated beta-catenin ablation, ectopic beta-TrCP expression enhanced the degradation. The involvement of beta-TrCP in beta-catenin degradation was also corroborated by the pull-down analysis and the concurrent down-regulation of known beta-TrCP substrates examined, including Wee1, Ikappabetaalpha, cdc25A, and nuclear factor-kappaB/p105. Furthermore, glycogen synthase kinase-3beta represented a key regulator in the effect of these thiazolidinedione derivatives on beta-catenin proteolysis even though these agents increased its phosphorylation level. It is noteworthy that this drug-induced beta-TrCP up-regulation was accompanied by the concomitant down-regulation of Skp2 and Fbw7, thereby affecting many of the target proteins of these two F-box proteins (such as p27 and cyclin E). As a consequence, the ability of troglitazone to target these F-box proteins provides a molecular basis to account for its reported effect on modulating the expression of aforementioned cell-cycle regulatory proteins. Despite this complicated mode of pharmacological actions, normal prostate epithelial cells, relative to LNCaP cells, were less susceptible to the effects of STG28 on modulating the expression of beta-catenin and beta-TrCP, suggesting the translation potential of using STG28 as a scaffold to develop more potent chemopreventive agents.
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Affiliation(s)
- Shuo Wei
- Division of Medicinal Chemistry, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA
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1076
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Li L, Zhou Y, Sun L, Xing G, Tian C, Sun J, Zhang L, He F. NuSAP is degraded by APC/C-Cdh1 and its overexpression results in mitotic arrest dependent of its microtubules' affinity. Cell Signal 2007; 19:2046-55. [PMID: 17618083 DOI: 10.1016/j.cellsig.2007.05.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Accepted: 05/28/2007] [Indexed: 11/18/2022]
Abstract
Microtubule associated proteins are involved in regulation of microtubule dynamics. Its mutation and dysregulation result in severe consequences such as mitotic block and apoptosis. NuSAP has been reported as a microtubule associated protein, depletion of which by RNAi results in spindle deficiency and cytokinesis failure. However, its role in regulation of cell cycle and how NuSAP protein is controlled during cell cycle progression still remains unclear. Here we show that NuSAP can be ubiquitinated and degraded by APC/C-hCdh1 E3 ligase. Evolutionally conserved KEN box functions as the degron of NuSAP. Overexpression of NuSAP induces mitotic arrest and the microtubule associated domain and nuclear localization are both required for NuSAP to induce mitotic arrest. Furthermore, overexpression of NuSAP results in cells accumulation with microtubule bundling and spindle deficiency. Thus, our results give evidence for the first time that NuSAP protein level is tightly regulated by the APC/C ubiquitin ligase complex and NuSAP induces mitotic arrest dependent of its microtubule affinity.
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Affiliation(s)
- Lu Li
- State Key Laboratory of Proteomics, Department of Genomics and Proteomics, Beijing Institute of Radiation Medicine, Beijing Proteome Research Center, 27 Taiping Road, Beijing 100850, China
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1077
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Genome-wide changes accompanying knockdown of fatty acid synthase in breast cancer. BMC Genomics 2007; 8:168. [PMID: 17565694 PMCID: PMC1913522 DOI: 10.1186/1471-2164-8-168] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Accepted: 06/12/2007] [Indexed: 01/22/2023] Open
Abstract
Background The lipogenic enzyme fatty acid synthase (FAS) is up-regulated in a wide variety of cancers, and is considered a potential metabolic oncogene by virtue of its ability to enhance tumor cell survival. Inhibition of tumor FAS causes both cell cycle arrest and apoptosis, indicating FAS is a promising target for cancer treatment. Results Here, we used gene expression profiling to conduct a global study of the cellular processes affected by siRNA mediated knockdown of FAS in MDA-MB-435 mammary carcinoma cells. The study identified 169 up-regulated genes (≥ 1.5 fold) and 110 down-regulated genes (≤ 0.67 fold) in response to knockdown of FAS. These genes regulate several aspects of tumor function, including metabolism, cell survival/proliferation, DNA replication/transcription, and protein degradation. Quantitative pathway analysis using Gene Set Enrichment Analysis software further revealed that the most pronounced effect of FAS knockdown was down-regulation in pathways that regulate lipid metabolism, glycolysis, the TCA cycle and oxidative phosphorylation. These changes were coupled with up-regulation in genes involved in cell cycle arrest and death receptor mediated apoptotic pathways. Conclusion Together these findings reveal a wide network of pathways that are influenced in response to FAS knockdown and provide new insight into the role of this enzyme in tumor cell survival and proliferation.
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1078
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Transcriptome changes and cAMP oscillations in an archaeal cell cycle. BMC Cell Biol 2007; 8:21. [PMID: 17562013 PMCID: PMC1906763 DOI: 10.1186/1471-2121-8-21] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 06/11/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The cell cycle of all organisms includes mass increase by a factor of two, replication of the genetic material, segregation of the genome to different parts of the cell, and cell division into two daughter cells. It is tightly regulated and typically includes cell cycle-specific oscillations of the levels of transcripts, proteins, protein modifications, and signaling molecules. Until now cell cycle-specific transcriptome changes have been described for four eukaryotic species ranging from yeast to human, but only for two prokaryotic species. Similarly, oscillations of small signaling molecules have been identified in very few eukaryotic species, but not in any prokaryote. RESULTS A synchronization procedure for the archaeon Halobacterium salinarum was optimized, so that nearly 100% of all cells divide in a time interval that is 1/4th of the generation time of exponentially growing cells. The method was used to characterize cell cycle-dependent transcriptome changes using a genome-wide DNA microarray. The transcript levels of 87 genes were found to be cell cycle-regulated, corresponding to 3% of all genes. They could be clustered into seven groups with different transcript level profiles. Cluster-specific sequence motifs were detected around the start of the genes that are predicted to be involved in cell cycle-specific transcriptional regulation. Notably, many cell cycle genes that have oscillating transcript levels in eukaryotes are not regulated on the transcriptional level in H. salinarum. Synchronized cultures were also used to identify putative small signaling molecules. H. salinarum was found to contain a basal cAMP concentration of 200 microM, considerably higher than that of yeast. The cAMP concentration is shortly induced directly prior to and after cell division, and thus cAMP probably is an important signal for cell cycle progression. CONCLUSION The analysis of cell cycle-specific transcriptome changes of H. salinarum allowed to identify a strategy of transcript level regulation that is different from all previously characterized species. The transcript levels of only 3% of all genes are regulated, a fraction that is considerably lower than has been reported for four eukaryotic species (6%-28%) and for the bacterium C. crescentus (19%). It was shown that cAMP is present in significant concentrations in an archaeon, and the phylogenetic profile of the adenylate cyclase indicates that this signaling molecule is widely distributed in archaea. The occurrence of cell cycle-dependent oscillations of the cAMP concentration in an archaeon and in several eukaryotic species indicates that cAMP level changes might be a phylogenetically old signal for cell cycle progression.
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1079
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Gupta R, Kus B, Fladd C, Wasmuth J, Tonikian R, Sidhu S, Krogan NJ, Parkinson J, Rotin D. Ubiquitination screen using protein microarrays for comprehensive identification of Rsp5 substrates in yeast. Mol Syst Biol 2007; 3:116. [PMID: 17551511 PMCID: PMC1911201 DOI: 10.1038/msb4100159] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Accepted: 04/24/2007] [Indexed: 01/25/2023] Open
Abstract
Ubiquitin-protein ligases (E3s) are responsible for target recognition and regulate stability, localization or function of their substrates. However, the substrates of most E3 enzymes remain unknown. Here, we describe the development of a novel proteomic in vitro ubiquitination screen using a protein microarray platform that can be utilized for the discovery of substrates for E3 ligases on a global scale. Using the yeast E3 Rsp5 as a test system to identify its substrates on a yeast protein microarray that covers most of the yeast (Saccharomyces cerevisiae) proteome, we identified numerous known and novel ubiquitinated substrates of this E3 ligase. Our enzymatic approach was complemented by a parallel protein microarray protein interaction study. Examination of the substrates identified in the analysis combined with phage display screening allowed exploration of binding mechanisms and substrate specificity of Rsp5. The development of a platform for global discovery of E3 substrates is invaluable for understanding the cellular pathways in which they participate, and could be utilized for the identification of drug targets.
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Affiliation(s)
- Ronish Gupta
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Bart Kus
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Christopher Fladd
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - James Wasmuth
- Program in Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Raffi Tonikian
- Banting & Best Department of Medical Research, University of Toronto, Canada
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Sachdev Sidhu
- Department of Protein Engineering, Genentech, South San Francisco, CA, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California-San Francisco, San Francisco, CA, USA
| | - John Parkinson
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Program in Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Daniela Rotin
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Program in Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8. Tel.: +1 416-813-5098; Fax: +1 416-813-8456;
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1080
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Lwin T, Hazlehurst LA, Dessureault S, Lai R, Bai W, Sotomayor E, Moscinski LC, Dalton WS, Tao J. Cell adhesion induces p27Kip1-associated cell-cycle arrest through down-regulation of the SCFSkp2 ubiquitin ligase pathway in mantle-cell and other non-Hodgkin B-cell lymphomas. Blood 2007; 110:1631-8. [PMID: 17502456 PMCID: PMC1975846 DOI: 10.1182/blood-2006-11-060350] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mounting evidence suggests that dynamic interactions between a tumor and its microenvironment play a critical role in tumor development, cell-cycle progression, and response to therapy. In this study, we used mantle cell lymphoma (MCL) as a model to characterize the mechanisms by which stroma regulate cell-cycle progression. We demonstrated that adhesion of MCL and other non-Hodgkin lymphoma (NHL) cells to bone marrow stromal cells resulted in a reversible G(1) arrest associated with elevated p27(Kip1) and p21 (WAF1) proteins. The adhesion-mediated p27(Kip1) and p21 increases were posttranslationally regulated via the down-regulation of Skp2, a subunit of SCF(Skp2) ubiquitin ligase. Overexpression of Skp2 in MCL decreased p27(Kip1), whereas inhibition of Skp2 by siRNA increased p27(Kip1) and p21 levels. Furthermore, we found cell adhesion up-regulated Cdh1 (an activating subunit of anaphase-promoting complex [APC] ubiquitin ligase), and reduction of Cdh1 by siRNA induced Skp2 accumulation and hence p27(Kip1) degradation, thus implicating Cdh1 as an upstream effector of the Skp2/p27(Kip1) signaling pathway. Overall, this report, for the first time, demonstrates that cell-cell contact controls the tumor cell cycle via ubiquitin-proteasome proteolytic pathways in MCL and other NHLs. The understanding of this novel molecular pathway may prove valuable in designing new therapeutic approaches for modifying tumor cell growth and response to therapy.
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MESH Headings
- Anaphase-Promoting Complex-Cyclosome
- Antigens, CD
- Bone Marrow Cells/metabolism
- Bone Marrow Cells/pathology
- Cadherins/genetics
- Cadherins/metabolism
- Cell Adhesion/drug effects
- Cell Adhesion/genetics
- Cell Line, Tumor
- Cyclin-Dependent Kinase Inhibitor p21/genetics
- Cyclin-Dependent Kinase Inhibitor p21/metabolism
- Cyclin-Dependent Kinase Inhibitor p27
- G1 Phase/drug effects
- G1 Phase/genetics
- Humans
- Intracellular Signaling Peptides and Proteins/antagonists & inhibitors
- Intracellular Signaling Peptides and Proteins/genetics
- Intracellular Signaling Peptides and Proteins/metabolism
- Lymphoma, B-Cell/enzymology
- Lymphoma, B-Cell/genetics
- Lymphoma, B-Cell/pathology
- Lymphoma, B-Cell/therapy
- Lymphoma, Mantle-Cell/enzymology
- Lymphoma, Mantle-Cell/genetics
- Lymphoma, Mantle-Cell/pathology
- Lymphoma, Mantle-Cell/therapy
- Models, Biological
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Proteasome Endopeptidase Complex/genetics
- Proteasome Endopeptidase Complex/metabolism
- RNA, Small Interfering/metabolism
- RNA, Small Interfering/pharmacology
- S-Phase Kinase-Associated Proteins/antagonists & inhibitors
- S-Phase Kinase-Associated Proteins/genetics
- S-Phase Kinase-Associated Proteins/metabolism
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Stromal Cells/metabolism
- Stromal Cells/pathology
- Ubiquitin/genetics
- Ubiquitin/metabolism
- Ubiquitin-Protein Ligase Complexes/genetics
- Ubiquitin-Protein Ligase Complexes/metabolism
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Affiliation(s)
- Tint Lwin
- Department of Interdisciplinary Oncology and Experimental Therapeutics Program, H. Lee Moffitt Cancer Center and Research Institute at the University of South Florida, Tampa, FL 33613, USA
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1081
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Nickeleit I, Zender S, Kossatz U, Malek NP. p27kip1: a target for tumor therapies? Cell Div 2007; 2:13. [PMID: 17488529 PMCID: PMC1872022 DOI: 10.1186/1747-1028-2-13] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Accepted: 05/09/2007] [Indexed: 11/27/2022] Open
Abstract
The cyclin kinase inhibitor p27kip1 acts as a potent tumor supressor protein in a variety of human cancers. Its expression levels correlate closely with the overall prognosis of the affected patient and often predict the outcome to different treatment modalities. In contrast to other tumor suppressor proteins p27 expression levels in tumor cells are frequently regulated by ubiquitin dependent proteolysis. Re-expression of p27 in cancer cells therefore does not require gene therapy but can be achieved by interfering with the protein turnover machinery. In this review we will summarize experimental results which highlight the potential use of p27 as a target for oncological therapies.
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Affiliation(s)
- Irina Nickeleit
- Institute for Molecular Biology, Hannover Medical School, Hannover, Germany
| | - Steffen Zender
- Institute for Molecular Biology, Hannover Medical School, Hannover, Germany
| | - Uta Kossatz
- Institute for Molecular Biology, Hannover Medical School, Hannover, Germany
| | - Nisar P Malek
- Institute for Molecular Biology, Hannover Medical School, Hannover, Germany
- Dept. of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
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1082
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Boylan KLM, Gosse MA, Staggs SE, Janz S, Grindle S, Kansas GS, Van Ness BG. A Transgenic Mouse Model of Plasma Cell Malignancy Shows Phenotypic, Cytogenetic, and Gene Expression Heterogeneity Similar to Human Multiple Myeloma. Cancer Res 2007; 67:4069-78. [PMID: 17483317 DOI: 10.1158/0008-5472.can-06-3699] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Multiple myeloma is an incurable plasma cell malignancy for which existing animal models are limited. We have previously shown that the targeted expression of the transgenes c-Myc and Bcl-X(L) in murine plasma cells produces malignancy that displays features of human myeloma, such as localization of tumor cells to the bone marrow and lytic bone lesions. We have isolated and characterized in vitro cultures and adoptive transfers of tumors from Bcl-xl/Myc transgenic mice. Tumors have a plasmablastic morphology and variable expression of CD138, CD45, CD38, and CD19. Spectral karyotyping analysis of metaphase chromosomes from primary tumor cell cultures shows that the Bcl-xl/Myc tumors contain a variety of chromosomal abnormalities, including trisomies, translocations, and deletions. The most frequently aberrant chromosomes are 12 and 16. Three sites for recurring translocations were also identified on chromosomes 4D, 12F, and 16C. Gene expression profiling was used to identify differences in gene expression between tumor cells and normal plasma cells (NPC) and to cluster the tumors into two groups (tumor groups C and D), with distinct gene expression profiles. Four hundred and ninety-five genes were significantly different between both tumor groups and NPCs, whereas 124 genes were uniquely different from NPCs in tumor group C and 204 genes were uniquely different from NPCs in tumor group D. Similar to human myeloma, the cyclin D genes are differentially dysregulated in the mouse tumor groups. These data suggest the Bcl-xl/Myc tumors are similar to a subset of plasmablastic human myelomas and provide insight into the specific genes and pathways underlying the human disease.
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1083
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Salon C, Merdzhanova G, Brambilla C, Brambilla E, Gazzeri S, Eymin B. E2F-1, Skp2 and cyclin E oncoproteins are upregulated and directly correlated in high-grade neuroendocrine lung tumors. Oncogene 2007; 26:6927-36. [PMID: 17471231 DOI: 10.1038/sj.onc.1210499] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The transcription factor E2F-1 plays a crucial role in the control of cellular growth. We previously reported its differential pattern of expression in human lung tumors. In this study, we have investigated the relationships linking the status of E2F-1 and a mediator of its proteasomal degradation, the S-phase kinase-associated protein 2 (Skp2) F-box protein. Using immunohistochemistry in a series of 129 lung tumors of all histological types, we demonstrate that Skp2 accumulates preferentially in high-grade neuroendocrine (HGNE) lung carcinomas (86%, P<0.0001), and show that Skp2 overexpression is associated with advanced stages (P<0.0001) and nodal metastasis (P<0.0001) in neuroendocrine (NE) lung tumors. Unexpectedly, we observe that Skp2 and E2F-1 expression directly correlates in NE lung tumors (P<0.0001). Moreover, using cellular models, we identify Skp2 as a new E2F-1 transcriptional target. Furthermore, we also provide evidence that Skp2 interacts physiologically with E2F-1 and stimulates its transcriptional activity toward the cyclin E promoter. Consistently, we demonstrate that cyclin E expression directly correlates with Skp2 (P<0.0001) and E2F-1 (P=0.0001) status in NE lung tumors. Overall, our data provide the first evidence of a direct and functional interconnection between the E2F-1, Skp2 and cyclin E oncoproteins in HGNE lung carcinomas.
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Affiliation(s)
- C Salon
- Equipe Bases Moléculaires de la Progression des Cancers du Poumon, Centre de Recherche INSERM U823, Institut Albert Bonniot, Grenoble Cedex, France
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1084
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Hwang CY, Kim IY, Kwon KS. Cytoplasmic localization and ubiquitination of p21(Cip1) by reactive oxygen species. Biochem Biophys Res Commun 2007; 358:219-25. [PMID: 17477906 DOI: 10.1016/j.bbrc.2007.04.120] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Accepted: 04/17/2007] [Indexed: 11/30/2022]
Abstract
Reactive oxygen species were previously shown to trigger p21(Cip1) protein degradation through a proteasome-dependent pathway, however the detailed mechanism of degradation remains to be elucidated. In this report, we showed that p21(Cip1) was degraded at an early phase after low dose H(2)O(2) treatment of a variety of cell types and that preincubation of cells with the antioxidant, N-acetylcysteine, prolonged p21(Cip1) half-life. A mutant p21(Cip1) in which all six lysines were changed to arginines was protected against H(2)O(2) treatment. Direct interaction between p21(Cip1) and Skp2 was elevated in the H(2)O(2)-treated cells. Disruption of the two nuclear export signal (NES) sequences in p21(Cip1), or treatment with leptomycin B blocked H(2)O(2)-induced p21(Cip1) degradation. Altogether, these results demonstrate that reactive oxygen species induce p21(Cip1) degradation through an NES-, Skp2-, and ubiquitin-dependent pathway.
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Affiliation(s)
- Chae Young Hwang
- Laboratory of Cell Signaling, Proteome Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-333, Republic of Korea
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1085
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Belaïdouni N, Marchal C, Benarous R, Besnard-Guérin C. Involvement of the betaTrCP in the ubiquitination and stability of the HIV-1 Vpu protein. Biochem Biophys Res Commun 2007; 357:688-93. [PMID: 17445772 DOI: 10.1016/j.bbrc.2007.03.195] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Accepted: 03/30/2007] [Indexed: 10/23/2022]
Abstract
The human immunodeficiency virus type 1 (HIV-1) Vpu protein binds to the CD4 receptor and targets it to the proteasome for degradation. This process requires the recruitment of human betaTrCP, a component of the Skp1-Cullin-F box (SCF) ubiquitin ligase complex, that interacts with phosphorylated Vpu molecules. Vpu, unlike other ligands of betaTrCP, has never been reported to be degraded. We provide evidence that Vpu, itself, is ubiquitinated and targeted for degradation by the proteasome. We demonstrate that the mutant Vpu2.6, which cannot interact with betaTrCP, is stable and, unlike wild-type Vpu, is not polyubiquitinated. These results suggest that betaTrCP is involved in Vpu polyubiquitination.
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Affiliation(s)
- Nadia Belaïdouni
- Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
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1086
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Abstract
Pituitary tumor-transforming gene-1 (PTTG1) is overexpressed in a variety of endocrine-related tumors, especially pituitary, thyroid, breast, ovarian, and uterine tumors, as well as nonendocrine-related cancers involving the central nervous, pulmonary, and gastrointestinal systems. Forced PTTG1 expression induces cell transformation in vitro and tumor formation in nude mice. In some tumors, high PTTG1 levels correlate with invasiveness, and PTTG1 has been identified as a key signature gene associated with tumor metastasis. Increasing evidence supports a multifunctional role of PTTG1 in cell physiology and tumorigenesis. Physiological PTTG1 properties include securin activity, DNA damage/repair regulation and involvement in organ development and metabolism. Tumorigenic mechanisms for PTTG1 action involve cell transformation and aneuploidy, apoptosis, and tumorigenic microenvironment feedback. This paper reviews recent advances in our understanding of PTTG1 structure and regulation and addresses known mechanisms of PTTG1 action. Recent knowledge gained from PTTG1-null mouse models and transgenic animals and their potential application to subcellular therapeutic targeting PTTG1 are discussed.
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Affiliation(s)
- George Vlotides
- Department of Medicine, Cedars-Sinai Medical Center, University of California School of Medicine, Los Angeles, California 90048, USA
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1087
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Tempé D, Brengues M, Mayonove P, Bensaad H, Lacrouts C, Morris MC. The alpha helix of ubiquitin interacts with yeast cyclin-dependent kinase subunit CKS1. Biochemistry 2007; 46:45-54. [PMID: 17198374 DOI: 10.1021/bi0614838] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ubiquitin serves as a molecular zipcode to direct and sort ubiquitinylated proteins into distinct biological pathways. Although novel modes of ubiquitin interaction have recently been characterized, conventional ubiquitin-binding domains (UBDs) recognize ubiquitin through a hydrophobic pocket centered around isoleucine 44 and lined by residues in beta sheets 3 and 4. In this study, we report a novel mode of interaction between ubiquitin and the cyclin-dependent kinase subunit of Saccharomyces cerevisiae, Cks1p, an adaptor protein involved in transcriptional regulation through recruitment of proteasomal subunits to gene promoters. Cks1p interacts specifically with monoubiquitin and tetraubiquitin with an affinity several orders of magnitude greater than that of other ubiquitin-binding domains and in an unconventional fashion, which differs from interactions documented so far between ubiquitin and conventional UBDs. The loop between helices alpha 1 and alpha 2, and to a minor extent the N-terminal alpha-helix of Cks1p, are involved in the interaction with the alpha-helix of ubiquitin, instead of its I44-centered hydrophobic pocket. Not only is this the first time the alpha-helix of ubiquitin is implicated in a protein/protein interaction, thereby shedding new light on the mechanisms of ubiquitin recognition, but also the first report of a direct physical interaction between ubiquitin and Cks1p, inferring a role for ubiquitin binding in the transcriptional function of Cks1p.
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Affiliation(s)
- Denis Tempé
- Department Dynamics of Assembly of Complex Systems, Centre de Recherches en Biochimie Macromoléculaire, CNRS FRE2593, 1919 Route de Mende, Montpellier 34293, France
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1088
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Sivaprasad U, Machida YJ, Dutta A. APC/C--the master controller of origin licensing? Cell Div 2007; 2:8. [PMID: 17319958 PMCID: PMC1810247 DOI: 10.1186/1747-1028-2-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Accepted: 02/23/2007] [Indexed: 11/15/2022] Open
Abstract
DNA replication must be tightly controlled to prevent initiation of a second round of replication until mitosis is complete. So far, components of the pre-replicative complex (Cdt1, Cdc6 and geminin) were considered key players in this regulation. In a new study, Machida and Dutta have shown that depletion of Emi1 caused cells to replicate their DNA more than once per cell cycle [1]. This effect was dependent on the ability of Emi1 to inhibit the APC/C. In addition to its role in regulating entry into mitosis, oscillation of APC/C activity regulates pre-RC formation: high APC/C activity in late M/G1 allows pre-RC formation and low APC/C activity in S/G2 prevents pre-RC formation for a second time thereby preventing rereplication. Each redundant pathway to prevent rereplication is dependent on regulating one of the pre-RC components, and all of the pathways are co-regulated by Emi1 through the APC/C. In this commentary we discuss how this new role of Emi1 adds to our understanding of the regulation of replication initiation. We also review the literature to analyze whether APC/C has a role in regulating endoreduplication (a normal state of polyploidy in some differentiated cells). Similarly a role of premature APC/C activation in genomic instability of tumors is discussed.
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Affiliation(s)
- Umasundari Sivaprasad
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Yuichi J Machida
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Anindya Dutta
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
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1089
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Nemajerova A, Mena P, Fingerle-Rowson G, Moll UM, Petrenko O. Impaired DNA damage checkpoint response in MIF-deficient mice. EMBO J 2007; 26:987-97. [PMID: 17290223 PMCID: PMC1852846 DOI: 10.1038/sj.emboj.7601564] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Accepted: 12/20/2006] [Indexed: 11/09/2022] Open
Abstract
Recent studies demonstrated that proinflammatory migration inhibitory factor(MIF) blocks p53-dependent apoptosis and interferes with the tumor suppressor activity of p53. To explore the mechanism underlying this MIF-p53 relationship, we studied spontaneous tumorigenesis in genetically matched p53-/- and MIF-/-p53-/- mice. We show that the loss of MIF expression aggravates the tumor-prone phenotype of p53-/- mice and predisposes them to a broader tumor spectrum, including B-cell lymphomas and carcinomas. Impaired DNA damage response is at the root of tumor predisposition of MIF-/-p53-/- mice. We provide evidence that MIF plays a role in regulating the activity of Cul1-containing SCF ubiquitin ligases. The loss of MIF expression uncouples Chk1/Chk2-responsive DNA damage checkpoints from SCF-dependent degradation of key cell-cycle regulators such as Cdc25A, E2F1 and DP1, creating conditions for the genetic instability of cells. These MIF effects depend on its association with the Jab1/CSN5 subunit of the COP9/CSN signalosome. Given that CSN plays a central role in the assembly of SCF complexes in vivo, regulation of Jab1/CSN5 by MIF is required to sustain optimal composition and function of the SCF complex.
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Affiliation(s)
- Alice Nemajerova
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY, USA
| | - Patricio Mena
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY, USA
| | - Gunter Fingerle-Rowson
- University Hospital Cologne, Medical Clinic I, Hematology and Oncology, Cologne, Germany
| | - Ute M Moll
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY, USA
| | - Oleksi Petrenko
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY, USA
- Department of Pathology, State University of New York at Stony Brook, BST L9, Stony Brook, NY 11794, USA. Tel.: +1 631 444 3520; Fax: +1 631 444 3424; E-mail:
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1090
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Estrabaud E, Lassot I, Blot G, Le Rouzic E, Tanchou V, Quemeneur E, Daviet L, Margottin-Goguet F, Benarous R. RASSF1C, an Isoform of the Tumor Suppressor RASSF1A, Promotes the Accumulation of β-Catenin by Interacting with βTrCP. Cancer Res 2007; 67:1054-61. [PMID: 17283138 DOI: 10.1158/0008-5472.can-06-2530] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Ras-association domain family 1 (RASSF1) gene has seven different isoforms; isoform A is a tumor-suppressor gene (RASSF1A). The promoter of RASSF1A is inactivated in many cancers, whereas the expression of another major isoform, RASSF1C, is not affected. Here, we show that RASSF1C, but not RASSF1A, interacts with betaTrCP. Binding of RASSF1C to betaTrCP involves serine 18 and serine 19 of the SS(18)GYXS(19) motif present in RASSF1C but not in RASSF1A. This motif is reminiscent of the canonical phosphorylation motif recognized by betaTrCP; however, surprisingly, the association between RASSF1C and betaTrCP does not occur via the betaTrCP substrate binding domain, the WD40 repeats. Overexpression of RASSF1C, but not of RASSF1A, resulted in accumulation and transcriptional activation of the beta-catenin oncogene, due to inhibition of its betaTrCP-mediated degradation. Silencing of RASSF1A by small interfering RNA was sufficient for beta-catenin to accumulate, whereas silencing of both RASSF1A and RASSF1C had no effect. Thus, RASSF1A and RASSF1C have opposite effects on beta-catenin degradation. Our results suggest that RASSF1C expression in the absence of RASSF1A could play a role in tumorigenesis.
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Affiliation(s)
- Emilie Estrabaud
- Institut Cochin, Département Maladies Infectieuses; Institut National de la Sante et de la Recherche Medicale U567, 27 rue du Faubourg Saint-Jacques, Bâtiment G Roussy, 75014 Paris, France
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1091
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Qi W, Yu H. KEN-Box-dependent Degradation of the Bub1 Spindle Checkpoint Kinase by the Anaphase-promoting Complex/Cyclosome. J Biol Chem 2007; 282:3672-9. [PMID: 17158872 DOI: 10.1074/jbc.m609376200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The spindle checkpoint is a cell cycle surveillance mechanism that ensures the fidelity of chromosome segregation during mitosis and meiosis. Bub1 is a protein serine-threonine kinase that plays multiple roles in chromosome segregation and the spindle checkpoint. In response to misaligned chromosomes, Bub1 directly inhibits the ubiquitin ligase activity of the anaphase-promoting complex or cyclosome (APC/C) by phosphorylating its activator Cdc20. The protein level and the kinase activity of Bub1 are regulated during the cell cycle; they peak in mitosis and are low in G1/S phase. Here we show that Bub1 is degraded during mitotic exit and that degradation of Bub1 is mediated by APC/C in complex with its activator Cdh1 (APC/C(Cdh1)). Overexpression of Cdh1 reduces the protein levels of ectopically expressed Bub1, whereas depletion of Cdh1 by RNA interference increases the level of the endogenous Bub1 protein. Bub1 is ubiquitinated by immunopurified APC/C(Cdh1) in vitro. We further identify two KEN-box motifs on Bub1 that are required for its degradation in vivo and ubiquitination in vitro. A Bub1 mutant protein with both KEN-boxes mutated is stable in cells but fails to elicit a cell cycle phenotype, indicating that degradation of Bub1 by APC/C(Cdh1) is not required for mitotic exit. Nevertheless, our study clearly demonstrates that Bub1, an APC/C inhibitor, is also an APC/C substrate. The antagonistic relationship between Bub1 and APC/C may help to prevent the premature accumulation of Bub1 during G1.
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Affiliation(s)
- Wei Qi
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
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1092
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De Preter K, Vandesompele J, Heimann P, Yigit N, Beckman S, Schramm A, Eggert A, Stallings RL, Benoit Y, Renard M, Paepe AD, Laureys G, Påhlman S, Speleman F. Human fetal neuroblast and neuroblastoma transcriptome analysis confirms neuroblast origin and highlights neuroblastoma candidate genes. Genome Biol 2007; 7:R84. [PMID: 16989664 PMCID: PMC1794547 DOI: 10.1186/gb-2006-7-9-r84] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 08/17/2006] [Accepted: 09/21/2006] [Indexed: 11/25/2022] Open
Abstract
Transcriptome profiling of neuroblasts and neuroblastoma tumor cells provides strong support for a neuroblast origin of neuroblastoma and highlights new candidate neuroblastoma genes Background Neuroblastoma tumor cells are assumed to originate from primitive neuroblasts giving rise to the sympathetic nervous system. Because these precursor cells are not detectable in postnatal life, their transcription profile has remained inaccessible for comparative data mining strategies in neuroblastoma. This study provides the first genome-wide mRNA expression profile of these human fetal sympathetic neuroblasts. To this purpose, small islets of normal neuroblasts were isolated by laser microdissection from human fetal adrenal glands. Results Expression of catecholamine metabolism genes, and neuronal and neuroendocrine markers in the neuroblasts indicated that the proper cells were microdissected. The similarities in expression profile between normal neuroblasts and malignant neuroblastomas provided strong evidence for the neuroblast origin hypothesis of neuroblastoma. Next, supervised feature selection was used to identify the genes that are differentially expressed in normal neuroblasts versus neuroblastoma tumors. This approach efficiently sifted out genes previously reported in neuroblastoma expression profiling studies; most importantly, it also highlighted a series of genes and pathways previously not mentioned in neuroblastoma biology but that were assumed to be involved in neuroblastoma pathogenesis. Conclusion This unique dataset adds power to ongoing and future gene expression studies in neuroblastoma and will facilitate the identification of molecular targets for novel therapies. In addition, this neuroblast transcriptome resource could prove useful for the further study of human sympathoadrenal biogenesis.
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Affiliation(s)
- Katleen De Preter
- Center for Medical Genetics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
| | - Jo Vandesompele
- Center for Medical Genetics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
| | - Pierre Heimann
- Department of Medical Genetics, University Hospital Erasme, Lenniksebaan, B-1070 Brussels, Belgium
| | - Nurten Yigit
- Center for Medical Genetics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
| | - Siv Beckman
- Division of Molecular Medicine, Department of Laboratory Medicine, Lund University, University Hospital MAS, SE-20502 Malmö, Sweden
| | - Alexander Schramm
- Department of Pediatric Oncology and Hematology, University Hospital of Essen, Hufelandstr, Essen 45122, Germany
| | - Angelika Eggert
- Department of Pediatric Oncology and Hematology, University Hospital of Essen, Hufelandstr, Essen 45122, Germany
| | - Raymond L Stallings
- Children's Cancer Research Institute, University of Texas Health Science Center, Floyd Curl Drive, Mail Code 7784, San Antonio, Texas 78229-3900, USA
| | - Yves Benoit
- Department of Pediatrics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
| | - Marleen Renard
- Department of Pediatrics, UZ Gasthuisberg, Herestraat, B-3000 Leuven, Belgium
| | - Anne De Paepe
- Center for Medical Genetics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
| | - Geneviève Laureys
- Department of Pediatrics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
| | - Sven Påhlman
- Division of Molecular Medicine, Department of Laboratory Medicine, Lund University, University Hospital MAS, SE-20502 Malmö, Sweden
| | - Frank Speleman
- Center for Medical Genetics, Ghent University Hospital, De Pintelaan, B-9000 Ghent, Belgium
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1093
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Abstract
Ubiquitin is an important regulator of diverse biological functions including cell cycle progression, apoptosis, cell proliferation, and DNA damage responses. Crucial proteins involved in the control of such diverse functions are modified by ubiquitin and are frequently altered during oncogenesis. Here, we define such proteins as key-nodes regulated by ubiquitin, discuss examples of their oncogenic aberrations, and indicate how pharmacologic manipulation of such molecular hubs might improve anticancer therapy.
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Affiliation(s)
- Nicola Crosetto
- Institute of Biochemistry II, Goethe University Hospital, Frankfort on the Main, Germany
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1094
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Kim AH, Bonni A. Thinking within the D box: initial identification of Cdh1-APC substrates in the nervous system. Mol Cell Neurosci 2007; 34:281-7. [PMID: 17223572 DOI: 10.1016/j.mcn.2006.11.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Accepted: 11/20/2006] [Indexed: 01/07/2023] Open
Abstract
The anaphase-promoting complex (APC) has a well-established role in cell cycle control, but recent exciting evidence has uncovered unexpected neurobiological functions for this complex E3 ubiquitin ligase. With its co-activator Cdh1, APC's effects upon the nervous system range from regulation of axon growth and patterning to development of synapses to neuronal survival. The Cdh1-APC substrates that control these biological processes in neurons are just beginning to be identified. These findings may offer a glimpse of the wide spectrum of neural activities that are orchestrated by Cdh1-APC.
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Affiliation(s)
- Albert H Kim
- Department of Pathology, Harvard Medical School, New Research Building, 77 Ave Louis Pasteur, Room 856, Boston, MA 02115, USA
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1095
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Sakai T, Sakaue H, Nakamura T, Okada M, Matsuki Y, Watanabe E, Hiramatsu R, Nakayama K, Nakayama KI, Kasuga M. Skp2 Controls Adipocyte Proliferation during the Development of Obesity. J Biol Chem 2007; 282:2038-46. [PMID: 17082193 DOI: 10.1074/jbc.m608144200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The increase in the mass of adipose tissue during the development of obesity can arise through an increase in cell size, an increase in cell number, or both. Here we show that long term maintenance of C57BL/6 mice on a high fat diet (for approximately 25 weeks) induces an initial increase in adipocyte size followed by an increase in adipocyte number in white adipose tissue. The latter effect was found to be accompanied by up-regulation of expression of the gene for the F-box protein Skp2 as well as by downregulation of the cyclin-dependent kinase inhibitor p27(Kip1), a principal target of the SCF(Skp2) ubiquitin ligase, in white adipose tissue. Ablation of Skp2 protected mice from the development of obesity induced either by a high fat diet or by the lethal yellow agouti (A(y)) mutation, and this protective action was due to inhibition of the increase in adipocyte number without an effect on adipocyte hypertrophy. The reduction in the number of adipocyte caused by Skp2 ablation also inhibited the development of obesity-related insulin resistance in the A(y) mutant mice, although the reduced number of beta cells and reduced level of insulin secretion in Skp2-deficient mice resulted in glucose intolerance. Our observations thus indicate that Skp2 controls adipocyte proliferation during the development of obesity.
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Affiliation(s)
- Tamon Sakai
- Department of Clinical Molecular Medicine, Division of Diabetes and Digestive and Kidney Diseases, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, USA
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1096
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Fujimuro M, Hayward SD, Yokosawa H. Molecular piracy: manipulation of the ubiquitin system by Kaposi's sarcoma-associated herpesvirus. Rev Med Virol 2007; 17:405-22. [PMID: 17688306 DOI: 10.1002/rmv.549] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Ubiquitination, one of several post-translational protein modifications, plays a key role in the regulation of cellular events, including protein degradation, signal transduction, endocytosis, protein trafficking, apoptosis and immune responses. Ubiquitin attachment at the lysine residue of cellular factors acts as a signal for endocytosis and rapid degradation by the 26S proteasome. It has recently been observed that viruses, especially oncogenic herpesviruses, utilise molecular piracy by encoding their own proteins to interfere with regulation of cell signalling. Kaposi's sarcoma- associated herpesvirus (KSHV) manipulates the ubiquitin system to facilitate cell proliferation, anti-apoptosis and evasion from immunity. In this review, we will describe the strategies used by KSHV at distinct stages of the viral life-cycle to control the ubiquitin system and promote oncogenesis and viral persistence.
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Affiliation(s)
- Masahiro Fujimuro
- Faculty of Pharmaceutical Sciences, Department of Biochemistry, Hokkaido University, Kita-ku, Sapporo, Japan.
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1097
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Perez-Torrado R, Yamada D, Defossez PA. Born to bind: the BTB protein-protein interaction domain. Bioessays 2006; 28:1194-202. [PMID: 17120193 DOI: 10.1002/bies.20500] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The BTB domain is a protein-protein interaction motif that is found throughout eukaryotes. It determines a unique tri-dimensional fold with a large interaction surface. The exposed residues are highly variable and can permit dimerization and oligomerization, as well as interaction with a number of other proteins. BTB-containing proteins are numerous and control cellular processes that range from actin dynamics to cell-cycle regulation. Here, we review findings in the field of transcriptional regulation to illustrate how the high variability of the BTB has allowed related transcription factors to evolve different functional abilities. We then report how recent work has showed that, in spite of their high sequence divergence and apparently unrelated functions, many BTB-containing proteins have at least one shared role: the recruitment of degradation targets to E3 ubiquitin ligase complexes. Taken together, these findings illustrate diverse and convergent functions of a versatile protein-protein interaction domain.
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1098
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Nencioni A, Grünebach F, Patrone F, Ballestrero A, Brossart P. Proteasome inhibitors: antitumor effects and beyond. Leukemia 2006; 21:30-6. [PMID: 17096016 DOI: 10.1038/sj.leu.2404444] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Proteasome inhibitors are emerging as effective drugs for the treatment of multiple myeloma and possibly certain subtypes of non-Hodgkin's lymphoma. Bortezomib (Velcade) is the first proteasome inhibitor proven to be clinically useful and will soon be followed by a second generation of small molecule inhibitors with improved pharmacological properties. Although it is now understood that certain types of malignancies have an exquisite dependence on a functional proteasome for their survival, the underlying reason(s) remain unclear as of now. In this context, addiction to nuclear factor-kappaB (NF-kappaB)-induced survival signals, activation of the unfolded protein response as well as a reduced proteasomal activity in differentiated plasma cells have all been proposed to justify proteasome inhibitors' activity in susceptible tissues. In addition to their anticancer properties, bortezomib and related drugs modulate inflammatory and immune responses by affecting function and survival of immune cells such as lymphocytes and dendritic cells. The present review offers an overview of the biological effects that have been involved in proteasome inhibitors' antitumor activity and suggests prospective future applications for these drugs based on their recently characterized anti-inflammatory and immunomodulatory effects.
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Affiliation(s)
- A Nencioni
- Department of Internal Medicine, University of Genova, Genova, Italy
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1099
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Itoh Y, Masuyama N, Nakayama K, Nakayama KI, Gotoh Y. The cyclin-dependent kinase inhibitors p57 and p27 regulate neuronal migration in the developing mouse neocortex. J Biol Chem 2006; 282:390-6. [PMID: 17092932 DOI: 10.1074/jbc.m609944200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal precursors remain in the proliferative zone of the developing mammalian neocortex until after they have undergone neuronal differentiation and cell cycle arrest. The newborn neurons then migrate away from the proliferative zone and enter the cortical plate. The molecules that coordinate migration with neuronal differentiation have been unclear. We have proposed in this study that the cdk inhibitors p57 and p27 play a role in this coordination. We have found that p57 and p27 mRNA increase upon neuronal differentiation of neocortical neuroepithelial cells. Knockdown of p57 by RNA interference resulted in a significant delay in the migration of neurons that entered the cortical plate but did not affect neuronal differentiation. Knockdown of p27 also inhibits neuronal migration in the intermediate zone as well as in the cortical plate, as reported by others. We have also found that knockdown of p27 increases p57 mRNA levels. These results suggest that both p57 and p27 play essential roles in neuronal migration and may, in concert, coordinate the timing of neuronal differentiation, migration, and possibly cell cycle arrest in neocortical development.
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Affiliation(s)
- Yasuhiro Itoh
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
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1100
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Dikic I, Crosetto N, Calatroni S, Bernasconi P. Targeting ubiquitin in cancers. Eur J Cancer 2006; 42:3095-102. [PMID: 17084074 DOI: 10.1016/j.ejca.2006.05.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Accepted: 05/10/2006] [Indexed: 11/15/2022]
Abstract
Ubiquitin (Ub) is a small protein modifier involved in cellular functions such as cell cycle, apoptosis, cell signalling, endocytosis, transcription and DNA repair. Ubiquitin operates as a reversible and highly versatile regulatory signal, which may be read and interpreted by an expanding number of Ub-binding domains (UBD). There is accumulating evidence that mutations or altered expression of ubiquitylating or de-ubiquitylating enzymes as well as of Ub-binding proteins affect crucial mediators of such functions and are found in several malignancies. Here we discuss how oncogenic alterations in the Ub system can be targeted by anti-cancer therapies.
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Affiliation(s)
- Ivan Dikic
- Institute of Biochemistry II, Goethe University Hospital, Theodor-Stern-Kai 7, D-60590 Frankfurt (Main), Germany.
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