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NF-κB Controls Cell Growth and Differentiation through Transcriptional Regulation of Cyclin D1

Guttridge, Denis C.; Albanese, Chris; Reuther, Julie Y.; Pestell, Richard G.; Baldwin, Albert S.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/1999 EN
Relevância na Pesquisa
105.47%
Accumulating evidence implicates the transcription factor NF-κB as a positive mediator of cell growth, but the molecular mechanism(s) involved in this process remains largely unknown. Here we use both a skeletal muscle differentiation model and normal diploid fibroblasts to gain insight into how NF-κB regulates cell growth and differentiation. Results obtained with the C2C12 myoblast cell line demonstrate that NF-κB functions as an inhibitor of myogenic differentiation. Myoblasts generated to lack NF-κB activity displayed defects in cellular proliferation and cell cycle exit upon differentiation. An analysis of cell cycle markers revealed that NF-κB activates cyclin D1 expression, and the results showed that this regulatory pathway is one mechanism by which NF-κB inhibits myogenesis. NF-κB regulation of cyclin D1 occurs at the transcriptional level and is mediated by direct binding of NF-κB to multiple sites in the cyclin D1 promoter. Using diploid fibroblasts, we demonstrate that NF-κB is required to induce cyclin D1 expression and pRb hyperphosphorylation and promote G1-to-S progression. Consistent with results obtained with the C2C12 differentiation model, we show that NF-κB also promotes cell growth in embryonic fibroblasts...

Inhibition of c-Jun N-Terminal Kinase 2 Expression Suppresses Growth and Induces Apoptosis of Human Tumor Cells in a p53-Dependent Manner

Potapova, Olga; Gorospe, Myriam; Dougherty, Ryan H.; Dean, Nicholas M.; Gaarde, William A.; Holbrook, Nikki J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /03/2000 EN
Relevância na Pesquisa
95.46%
c-Jun N-terminal kinase (JNK) plays a critical role in coordinating the cellular response to stress and has been implicated in regulating cell growth and transformation. To investigate the growth-regulatory functions of JNK1 and JNK2, we used specific antisense oligonucleotides (AS) to inhibit their expression. A survey of several human tumor cell lines revealed that JNKAS treatment markedly inhibited the growth of cells with mutant p53 status but not that of cells with normal p53 function. To further examine the influence of p53 on cell sensitivity to JNKAS treatment, we compared the responsiveness of RKO, MCF-7, and HCT116 cells with normal p53 function to that of RKO E6, MCF-7 E6, and HCT116 p53−/−, which were rendered p53 deficient by different methods. Inhibition of JNK2 (and to a lesser extent JNK1) expression dramatically reduced the growth of p53-deficient cells but not that of their normal counterparts. JNK2AS-induced growth inhibition was correlated with significant apoptosis. JNK2AS treatment induced the expression of the cyclin-dependent kinase inhibitor p21Cip1/Waf1 in parental MCF-7, RKO, and HCT116 cells but not in the p53-deficient derivatives. That p21Cip1/Waf1 expression contributes to the survival of JNK2AS-treated cells was supported by additional experiments demonstrating that p21Cip1/Waf1 deficiency in HCT116 cells also results in heightened sensitivity to JNKAS treatment. Our results indicate that perturbation of JNK2 expression adversely affects the growth of otherwise nonstressed cells. p53 and its downstream effector p21Cip1/Waf1 are important in counteracting these detrimental effects and promoting cell survival.

Polarized Growth Controls Cell Shape and Bipolar Bud Site Selection in Saccharomyces cerevisiae

Sheu, Yi-Jun; Barral, Yves; Snyder, Michael
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/2000 EN
Relevância na Pesquisa
85.51%
We examined the relationship between polarized growth and division site selection, two fundamental processes important for proper development of eukaryotes. Diploid Saccharomyces cerevisiae cells exhibit an ellipsoidal shape and a specific division pattern (a bipolar budding pattern). We found that the polarity genes SPA2, PEA2, BUD6, and BNI1 participate in a crucial step of bud morphogenesis, apical growth. Deleting these genes results in round cells and diminishes bud elongation in mutants that exhibit pronounced apical growth. Examination of distribution of the polarized secretion marker Sec4 demonstrates that spa2Δ, pea2Δ, bud6Δ, and bni1Δ mutants fail to concentrate Sec4 at the bud tip during apical growth and at the division site during repolarization just prior to cytokinesis. Moreover, cell surface expansion is not confined to the distal tip of the bud in these mutants. In addition, we found that the p21-activated kinase homologue Ste20 is also important for both apical growth and bipolar bud site selection. We further examined how the duration of polarized growth affects bipolar bud site selection by using mutations in cell cycle regulators that control the timing of growth phases. The grr1Δ mutation enhances apical growth by stabilizing G1 cyclins and increases the distal-pole budding in diploids. Prolonging polarized growth phases by disrupting the G2/M cyclin gene CLB2 enhances the accuracy of bud site selection in wild-type...

TEL, a Putative Tumor Suppressor, Modulates Cell Growth and Cell Morphology of Ras-Transformed Cells While Repressing the Transcription of stromelysin-1

Fenrick, Randy; Wang, Lilin; Nip, John; Amann, Joseph M.; Rooney, Robert J.; Walker-Daniels, Jennifer; Crawford, Howard C.; Hulboy, Diana L.; Kinch, Michael S.; Matrisian, Lynn M.; Hiebert, Scott W.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2000 EN
Relevância na Pesquisa
95.42%
TEL is a member of the ETS family of transcription factors that interacts with the mSin3 and SMRT corepressors to regulate transcription. TEL is biallelically disrupted in acute leukemia, and loss of heterozygosity at the TEL locus has been observed in various cancers. Here we show that expression of TEL in Ras-transformed NIH 3T3 cells inhibits cell growth in soft agar and in normal cultures. Unexpectedly, cells expressing both Ras and TEL grew as aggregates. To begin to explain the morphology of Ras-plus TEL-expressing cells, we demonstrated that the endogenous matrix metalloproteinase stromelysin-1 was repressed by TEL. TEL bound sequences in the stromelysin-1 promoter and repressed the promoter in transient-expression assays, suggesting that it is a direct target for TEL-mediated regulation. Mutants of TEL that removed a binding site for the mSin3A corepressor but retained the ETS domain failed to repress stromelysin-1. When BB-94, a matrix metalloproteinase inhibitor, was added to the culture medium of Ras-expressing cells, it caused a cell aggregation phenotype similar to that caused by TEL expression. In addition, TEL inhibited the invasiveness of Ras-transformed cells in vitro and in vivo. Our results suggest that TEL acts as a tumor suppressor...

Pie1, a Protein Interacting with Mec1, Controls Cell Growth and Checkpoint Responses in Saccharomyces cerevisiae

Wakayama, Tatsushi; Kondo, Tae; Ando, Seiko; Matsumoto, Kunihiro; Sugimoto, Katsunori
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2001 EN
Relevância na Pesquisa
105.45%
In eukaryotes, the ATM and ATR family proteins play a critical role in the DNA damage and replication checkpoint controls. These proteins are characterized by a kinase domain related to the phosphatidylinositol 3-kinase, but they have the ability to phosphorylate proteins. In budding yeast, the ATR family protein Mec1/Esr1 is essential for checkpoint responses and cell growth. We have isolated the PIE1 gene in a two-hybrid screen for proteins that interact with Mec1, and we show that Pie1 interacts physically with Mec1 in vivo. Like MEC1, PIE1 is essential for cell growth, and deletion of the PIE1 gene causes defects in the DNA damage and replication block checkpoints similar to those observed in mec1Δ mutants. Rad53 hyperphosphorylation following DNA damage and replication block is also decreased in pie1Δ cells, as in mec1Δ cells. Pie1 has a limited homology to fission yeast Rad26, which forms a complex with the ATR family protein Rad3. Mutation of the region in Pie1 homologous to Rad26 results in a phenotype similar to that of the pie1Δ mutation. Mec1 protein kinase activity appears to be essential for checkpoint responses and cell growth. However, Mec1 kinase activity is unaffected by the pie1Δ mutation, suggesting that Pie1 regulates some essential function other than Mec1 kinase activity. Thus...

VHL Induces Renal Cell Differentiation and Growth Arrest through Integration of Cell-Cell and Cell-Extracellular Matrix Signaling

Davidowitz, Eliot J.; Schoenfeld, Alan R.; Burk, Robert D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2001 EN
Relevância na Pesquisa
85.52%
Mutations in the von Hippel-Lindau (VHL) gene are involved in the family cancer syndrome for which it is named and the development of sporadic renal cell cancer (RCC). Reintroduction of VHL into RCC cells lacking functional VHL [VHL(−)] can suppress their growth in nude mice, but not under standard tissue culture conditions. To examine the hypothesis that the tumor suppressor function of VHL requires signaling through contact with extracellular matrix (ECM), 786-O VHL(−) RCC cells and isogenic sublines stably expressing VHL gene products [VHL(+)] were grown on ECMs. Cell-cell and cell-ECM signalings were required to elicit VHL-dependent differences in growth and differentiation. VHL(+) cells differentiated into organized epithelial sheets, whereas VHL(−) cells were branched and disorganized. VHL(+) cells grown to high density on collagen I underwent growth arrest, whereas VHL(−) cells continued to proliferate. Integrin levels were up-regulated in VHL(−) cells, and cell adhesion was down-regulated in VHL(+) cells during growth at high cell density. Hepatocyte nuclear factor 1α, a transcription factor and global activator of proximal tubule-specific genes in the nephron, was markedly up-regulated in VHL(+) cells grown at high cell density. These data indicate that VHL can induce renal cell differentiation and mediate growth arrest through integration of cell-cell and cell-ECM signals.

The Cbk1p Pathway Is Important for Polarized Cell Growth and Cell Separation in Saccharomyces cerevisiae

Bidlingmaier, Scott; Weiss, Eric L.; Seidel, Chris; Drubin, David G.; Snyder, Michael
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2001 EN
Relevância na Pesquisa
95.48%
During the early stages of budding, cell wall remodeling and polarized secretion are concentrated at the bud tip (apical growth). The CBK1 gene, encoding a putative serine/threonine protein kinase, was identified in a screen designed to isolate mutations that affect apical growth. Analysis of cbk1Δ cells reveals that Cbk1p is required for efficient apical growth, proper mating projection morphology, bipolar bud site selection in diploid cells, and cell separation. Epitope-tagged Cbk1p localizes to both sides of the bud neck in late anaphase, just prior to cell separation. CBK1 and another gene, HYM1, were previously identified in a screen for genes involved in transcriptional repression and proposed to function in the same pathway. Deletion of HYM1 causes phenotypes similar to those observed in cbk1Δ cells and disrupts the bud neck localization of Cbk1p. Whole-genome transcriptional analysis of cbk1Δ suggests that the kinase regulates the expression of a number of genes with cell wall-related functions, including two genes required for efficient cell separation: the chitinase-encoding gene CTS1 and the glucanase-encoding gene SCW11. The Ace2p transcription factor is required for expression of CTS1 and has been shown to physically interact with Cbk1p. Analysis of ace2Δ cells reveals that Ace2p is required for cell separation but not for polarized growth. Our results suggest that Cbk1p and Hym1p function to regulate two distinct cell morphogenesis pathways: an ACE2-independent pathway that is required for efficient apical growth and mating projection formation and an ACE2-dependent pathway that is required for efficient cell separation following cytokinesis. Cbk1p is most closely related to the Neurospora crassa Cot-1; Schizosaccharomyces pombe Orb6; Caenorhabditis elegans...

Critical Role of the HMGI(Y) Proteins in Adipocytic Cell Growth and Differentiation

Melillo, Rosa Marina; Pierantoni, Giovanna Maria; Scala, Stefania; Battista, Sabrina; Fedele, Monica; Stella, Antonella; De Biasio, Maria Cristina; Chiappetta, Gennaro; Fidanza, Vincenzo; Condorelli, Gianluigi; Santoro, Massimo; Croce, Carlo M.; Viglietto
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2001 EN
Relevância na Pesquisa
105.45%
The high-mobility group I (HMGI) nonhistone chromosomal proteins HMGI(Y) and HMGI-C have been implicated in defining chromatin structure and in regulating the transcription of several genes. These proteins have been implicated in adipocyte homeostasis: a severe deficiency of fat tissue is found in mice with targeted disruption of the HMGI-C locus, and lipomagenesis in humans is frequently associated with somatic mutations of HMGI genes. The aim of this study was to examine the role of HMGI(Y) proteins in adipocytic cell growth and differentiation. First, we found that differentiation of the preadipocytic 3T3-L1 cell line caused early induction of HMGI(Y) gene expression. Suppression of HMGI(Y) expression by antisense technology dramatically increased the growth rate and impaired adipocytic differentiation in these cells. The process of adipogenic differentiation involves the interplay of several transcription factors, among which is the CCAAT/enhancer-binding protein (C/EBP) family of proteins. These factors are required for the transcriptional activation of adipocyte-specific genes. We also tested the hypothesis that HMGI(Y) might participate in transcriptional control of adipocyte-specific promoters. We found that HMGI(Y) proteins bind C/EBPβ in vivo and in vitro. Furthermore...

NoBP, a Nuclear Fibroblast Growth Factor 3 Binding Protein, Is Cell Cycle Regulated and Promotes Cell Growth

Reimers, Kerstin; Antoine, Marianne; Zapatka, Marcus; Blecken, Volker; Dickson, Clive; Kiefer, Paul
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2001 EN
Relevância na Pesquisa
95.46%
Secreted and nuclear forms of fibroblast growth factor 3 (FGF3) have opposing effects on cells. The secreted form stimulates cell growth and transformation, while the nuclear form inhibits DNA synthesis and cell proliferation. By using the yeast two-hybrid system we have identified a nucleolar FGF3 binding protein (NoBP) which coimmunoprecipitated and colocalized with FGF3 in transfected COS-1 cells. Characterization of the NoBP binding domain of FGF3 exactly matched the sequence requirements of FGF3 for its translocation into the nucleoli, suggesting that NoBP might be the nucleolar binding partner of FGF3 essential for its nucleolus localization. Carboxyl-terminal domains of NoBP contain linear nuclear and nucleolar targeting motifs which are capable of directing a heterologous protein β-galactosidase to the nucleus and the nucleoli. While NoBP expression was detected in all analyzed proliferating established cell lines, NoBP transcription was rapidly downregulated in the promyelocytic leukemia cell line HL60 when induced to differentiate. Analysis on the expression pattern of NoBP mRNA throughout the cell cycle in HeLa cells synchronized by lovastatin demonstrated a substantial upregulation during the late G1/early S phase. NoBP overexpression conferred a proliferating effect onto NIH 3T3 cells and can counteract the inhibitory effect of nuclear FGF3...

Growth Factors Can Influence Cell Growth and Survival through Effects on Glucose Metabolism

Vander Heiden, Matthew G.; Plas, David R.; Rathmell, Jeffrey C.; Fox, Casey J.; Harris, Marian H.; Thompson, Craig B.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2001 EN
Relevância na Pesquisa
95.49%
Cells from multicellular organisms are dependent upon exogenous signals for survival, growth, and proliferation. The relationship among these three processes was examined using an interleukin-3 (IL-3)-dependent cell line. No fixed dose of IL-3 determined the threshold below which cells underwent apoptosis. Instead, increasing growth factor concentrations resulted in progressive shortening of the G1 phase of the cell cycle and more rapid proliferative expansion. Increased growth factor concentrations also resulted in proportional increases in glycolytic rates. Paradoxically, cells growing in high concentrations of growth factor had an increased susceptibility to cell death upon growth factor withdrawal. This susceptibility correlated with the magnitude of the change in the glycolytic rate following growth factor withdrawal. To investigate whether changes in the availability of glycolytic products influence mitochondrion-initiated apoptosis, we artificially limited glycolysis by manipulating the glucose levels in the medium. Like growth factor withdrawal, glucose limitation resulted in Bax translocation, a decrease in mitochondrial membrane potential, and cytochrome c redistribution to the cytosol. In contrast, increasing cell autonomous glucose uptake by overexpression of Glut1 significantly delayed apoptosis following growth factor withdrawal. These data suggest that a primary function of growth factors is to regulate glucose uptake and metabolism and thus maintain mitochondrial homeostasis and enable anabolic pathways required for cell growth. Consistent with this hypothesis...

Different Domains of the Essential GTPase Cdc42p Required for Growth and Development of Saccharomyces cerevisiae

Mösch, Hans-Ulrich; Köhler, Tim; Braus, Gerhard H.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/2001 EN
Relevância na Pesquisa
95.55%
In budding yeast, the Rho-type GTPase Cdc42p is essential for cell division and regulates pseudohyphal development and invasive growth. Here, we isolated novel Cdc42p mutant proteins with single-amino-acid substitutions that are sufficient to uncouple functions of Cdc42p essential for cell division from regulatory functions required for pseudohyphal development and invasive growth. In haploid cells, Cdc42p is able to regulate invasive growth dependent on and independent of FLO11 gene expression. In diploid cells, Cdc42p regulates pseudohyphal development by controlling pseudohyphal cell (PH cell) morphogenesis and invasive growth. Several of the Cdc42p mutants isolated here block PH cell morphogenesis in response to nitrogen starvation without affecting morphology or polarity of yeast form cells in nutrient-rich conditions, indicating that these proteins are impaired for certain signaling functions. Interaction studies between development-specific Cdc42p mutants and known effector proteins indicate that in addition to the p21-activated (PAK)-like protein kinase Ste20p, the Cdc42p/Rac-interactive-binding domain containing Gic1p and Gic2p proteins and the PAK-like protein kinase Skm1p might be further effectors of Cdc42p that regulate pseudohyphal and invasive growth.

Modulated Expression of the Epidermal Growth Factor-Like Homeotic Protein dlk Influences Stromal-Cell–Pre-B-Cell Interactions, Stromal Cell Adipogenesis, and Pre-B-Cell Interleukin-7 Requirements

Bauer, Steven R.; Ruiz-Hidalgo, María José; Rudikoff, Eva K.; Goldstein, Julia; Laborda, Jorge
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/1998 EN
Relevância na Pesquisa
95.48%
A close relationship exists between adipocyte differentiation of stromal cells and their capacity to support hematopoiesis. The molecular basis for this is unknown. We have studied whether dlk, an epidermal growth factor-like molecule that intervenes in adipogenesis and fetal liver hematopoiesis, affects both stromal cell adipogenesis and B-cell lymphopoiesis in an established pre-B-cell culture system. Pre-B-cell cultures require both soluble interleukin-7 (IL-7) and interactions with stromal cells to promote cell growth and prevent B-cell maturation or apoptosis. We found that BALB/c 3T3 fibroblasts express dlk and function as stromal cells. Transfection of these cells with antisense dlk decreased dlk expression and increased insulin-induced adipocytic differentiation. When antisense transfectants were used as stroma, IL-7 was no longer required to support the growth of pre-B cells and prevent maturation or apoptosis. Antisense dlk transfectants of S10 stromal cells also promoted pre-B-cell growth in the absence of IL-7. These results show that modulation of dlk on stromal cells can influence their adipogenesis and the IL-7 requirements of the pre-B cells growing in contact with them. These results indicate that dlk influences differentiation signals directed both to the stromal cells and to the lymphocyte precursors...

Adenovirus E1A-Regulated Transcription Factor p120E4F Inhibits Cell Growth and Induces the Stabilization of the cdk Inhibitor p21WAF1

Fernandes, Elma R.; Zhang, Jun Yuan; Rooney, Robert J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/1998 EN
Relevância na Pesquisa
105.46%
Adenovirus E1A proteins influence cell growth and phenotype through physical interactions with cellular proteins that regulate basic processes such as cell cycle progression, DNA synthesis, and differentiation. p120E4F is a low-abundance cellular transcription factor that represses the adenovirus E4 promoter and is regulated by E1A, through a phosphorylation-induced reduction of its DNA binding activity, to permit activation of the E4 promoter during early infection. To determine the normal biological role of p120E4F, we assessed its ability to influence fibroblast cell growth and transformation. p120E4F suppressed NIH 3T3 fibroblast colony formation but had little effect when coexpressed with E1A and/or activated ras. Cells that overexpressed p120E4F were inhibited in their ability to enter S phase, had elevated levels of the cdk inhibitor p21WAF1, and reduced cyclin D-cdk4/6 kinase activity. The increase of p21WAF1 levels occurred through a p53-independent posttranscriptional mechanism that included a three- to fourfold increase in the half-life of p21WAF1 protein. Coexpression of activated ras with p120E4F stimulated cyclin D1 expression, elevated cyclin D-cdk4/6 kinase activity, and accelerated cell growth. These data suggest an important role for p120E4F in normal cell division and demonstrate that p21WAF1 can be regulated by protein turnover.

Autoinhibitory Regulation of p73 by ΔNp73 To Modulate Cell Survival and Death through a p73-Specific Target Element within the ΔNp73 Promoter

Nakagawa, Takahito; Takahashi, Masato; Ozaki, Toshinori; Watanabe, Ken-ichi; Todo, Satoru; Mizuguchi, Hiroyuki; Hayakawa, Takao; Nakagawara, Akira
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2002 EN
Relevância na Pesquisa
95.4%
p73 is a p53-related tumor suppressor but is also induced by oncogene products such as E2F-1, raising a question as to whether p73 is a tumor suppressor gene or oncogene. Unlike p53, p73 has several variants, including ΔNp73, which lacks the NH2-terminal transactivation domain. Although, in developing neurons, ΔNp73 is expressed abundantly and seems to inhibit the proapoptotic function of p53, the role of p73 and ΔNp73 and their regulatory mechanism in cell growth and differentiation are poorly understood. Here we report that p73, but not p53, directly activates the transcription of endogenous ΔNp73 by binding to the p73-specific target element located at positions −76 to −57 within the ΔNp73 promoter region. The activation of ΔNp73 promoter by p63 was marginal. ΔNp73 was associated with p73α, p73β, and p53, as demonstrated by immunoprecipitation assays, and inhibited their transactivation activities when we used reporters of Mdm2, Bax, or ΔNp73 itself in SAOS-2 cells. Furthermore, induction or overexpression of ΔNp73 promoted cell survival by competing with p53 and p73 itself. Thus, our results suggest that the negative feedback regulation of p73 by its target ΔNp73 is a novel autoregulatory system for modulating cell survival and death.

Absence of the CAAX Endoprotease Rce1: Effects on Cell Growth and Transformation

Bergo, Martin O.; Ambroziak, Patricia; Gregory, Cria; George, Amanda; Otto, James C.; Kim, Edward; Nagase, Hiroki; Casey, Patrick J.; Balmain, Allan; Young, Stephen G.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/2002 EN
Relevância na Pesquisa
105.46%
After isoprenylation, the Ras proteins and other CAAX proteins undergo two additional enzymatic modifications—endoproteolytic release of the last three amino acids of the protein by the protease Rce1 and methylation of the carboxyl-terminal isoprenylcysteine by the methyltransferase Icmt. This postisoprenylation processing is thought to be important for the association of Ras proteins with membranes. Blocking postisoprenylation processing, by inhibiting Rce1, has been suggested as a potential approach for retarding cell growth and blocking cellular transformation. The objective of this study was to develop a cell culture system for addressing these issues. We generated mice with a conditional Rce1 allele (Rce1flox) and produced Rce1flox/flox fibroblasts. Cre-mediated excision of Rce1 (thereby producing Rce1Δ/Δ fibroblasts) eliminated Ras endoproteolytic processing and methylation and caused a partial mislocalization of truncated K-Ras and H-Ras fusion proteins within cells. Rce1Δ/Δ fibroblasts grew more slowly than Rce1flox/flox fibroblasts. The excision of Rce1 also reduced Ras-induced transformation, as judged by the growth of colonies in soft agar. The excision of Rce1 from a Rce1flox/flox skin carcinoma cell line also significantly retarded the growth of cells...

Ash1 Protein, an Asymmetrically Localized Transcriptional Regulator, Controls Filamentous Growth and Virulence of Candida albicans

Inglis, Diane O.; Johnson, Alexander D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2002 EN
Relevância na Pesquisa
95.41%
In response to a number of distinct environmental conditions, the fungal pathogen Candida albicans undergoes a morphological transition from a round, yeast form to a series of elongated, filamentous forms. This transition is believed to be critical for virulence in a mouse model of disseminated candidiasis. Here we describe the characterization of C. albicans ASH1, a gene that encodes an asymmetrically localized transcriptional regulatory protein involved in this response. We show that C. albicans ash1 mutants are defective in responding to some filament-inducing conditions. We also show that Ash1p is preferentially localized to daughter cell nuclei in the budding-yeast form of C. albicans cell growth and to the hyphal tip cells in growing filaments. Thus, Ash1p “marks” newly formed cells and presumably directs a specialized transcriptional program in these cells. Finally, we show that ASH1 is required for full virulence of C. albicans in a mouse model of disseminated candidiasis.

Polysialic Acid Directs Tumor Cell Growth by Controlling Heterophilic Neural Cell Adhesion Molecule Interactions

Seidenfaden, Ralph; Krauter, Andrea; Schertzinger, Frank; Gerardy-Schahn, Rita; Hildebrandt, Herbert
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2003 EN
Relevância na Pesquisa
95.45%
Polysialic acid (PSA), a carbohydrate polymer attached to the neural cell adhesion molecule (NCAM), promotes neural plasticity and tumor malignancy, but its mode of action is controversial. Here we establish that PSA controls tumor cell growth and differentiation by interfering with NCAM signaling at cell-cell contacts. Interactions between cells with different PSA and NCAM expression profiles were initiated by enzymatic removal of PSA and by ectopic expression of NCAM or PSA-NCAM. Removal of PSA from the cell surface led to reduced proliferation and activated extracellular signal-regulated kinase (ERK), inducing enhanced survival and neuronal differentiation of neuroblastoma cells. Blocking with an NCAM-specific peptide prevented these effects. Combinatorial transinteraction studies with cells and membranes with different PSA and NCAM phenotypes revealed that heterophilic NCAM binding mimics the cellular responses to PSA removal. In conclusion, our data demonstrate that PSA masks heterophilic NCAM signals, having a direct impact on tumor cell growth. This provides a mechanism for how PSA may promote the genesis and progression of highly aggressive PSA-NCAM-positive tumors.

mTOR Controls Cell Cycle Progression through Its Cell Growth Effectors S6K1 and 4E-BP1/Eukaryotic Translation Initiation Factor 4E

Fingar, Diane C.; Richardson, Celeste J.; Tee, Andrew R.; Cheatham, Lynn; Tsou, Christina; Blenis, John
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/2004 EN
Relevância na Pesquisa
95.46%
The mammalian target of rapamycin (mTOR) integrates nutrient and mitogen signals to regulate cell growth (increased cell mass and cell size) and cell division. The immunosuppressive drug rapamycin inhibits cell cycle progression via inhibition of mTOR; however, the signaling pathways by which mTOR regulates cell cycle progression have remained poorly defined. Here we demonstrate that restoration of mTOR signaling (by using a rapamycin-resistant mutant of mTOR) rescues rapamycin-inhibited G1-phase progression, and restoration of signaling along the mTOR-dependent S6K1 or 4E-BP1/eukaryotic translation initiation factor 4E (eIF4E) pathways provides partial rescue. Furthermore, interfering RNA-mediated reduction of S6K1 expression or overexpression of mTOR-insensitive 4E-BP1 isoforms that block eIF4E activity inhibit G1-phase progression individually and additively. Thus, the activities of both the S6K1 and 4E-BP1/eIF4E pathways are required for and independently mediate mTOR-dependent G1-phase progression. In addition, overexpression of constitutively active mutants of S6K1 or wild-type eIF4E accelerates serum-stimulated G1-phase progression, and stable expression of wild-type S6K1 confers a proliferative advantage in low-serum-containing media...

Id2 and Id3 Define the Potency of Cell Proliferation and Differentiation Responses to Transforming Growth Factor β and Bone Morphogenetic Protein†

Kowanetz, Marcin; Valcourt, Ulrich; Bergström, Rosita; Heldin, Carl-Henrik; Moustakas, Aristidis
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/2004 EN
Relevância na Pesquisa
95.45%
Transforming growth factors β (TGF-βs) inhibit growth of epithelial cells and induce differentiation changes, such as epithelial-mesenchymal transition (EMT). On the other hand, bone morphogenetic proteins (BMPs) weakly affect epithelial cell growth and do not induce EMT. Smad4 transmits signals from both TGF-β and BMP pathways. Stimulation of Smad4-deficient epithelial cells with TGF-β1 or BMP-7 in the absence or presence of exogenous Smad4, followed by cDNA microarray analysis, revealed 173 mostly Smad4-dependent, TGF-β-, or BMP-responsive genes. Among 25 genes coregulated by both factors, inhibitors of differentiation Id2 and Id3 showed long-term repression by TGF-β and sustained induction by BMP. The opposing regulation of Id genes is critical for proliferative and differentiation responses. Hence, ectopic Id2 or Id3 expression renders epithelial cells refractory to growth inhibition and EMT induced by TGF-β, phenocopying the BMP response. Knockdown of endogenous Id2 or Id3 sensitizes epithelial cells to BMP, leading to robust growth inhibition and induction of transdifferentiation. Thus, Id genes sense Smad signals and create a permissive or refractory nuclear environment that defines decisions of cell fate and proliferation.

The Intracellular Form of Notch Blocks Transforming Growth Factor β-Mediated Growth Arrest in Mv1Lu Epithelial Cells

Rao, Prakash; Kadesch, Tom
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2003 EN
Relevância na Pesquisa
85.51%
Notch signaling influences a variety of cell fate decisions during development, and constitutive activation of the pathway can provoke unbridled cell growth and cancer. The mechanisms by which Notch affects cell growth are not well established. We describe here a novel link between Notch and cell cycle control. We found that Mv1Lu epithelial cells harboring an oncogenic form of Notch (NICD) are resistant to the cell cycle-inhibitory effects of transforming growth factor β (TGF-β). NICD did not affect TGF-β signaling per se but blocked induction of the Cdk inhibitor p15INK4B. c-Myc, whose down-regulation by TGF-β is required for p15INK4B induction, remained elevated in the NICD-expressing cells. c-Myc expression was also maintained in low serum, indicating that Notch's effects on c-Myc are not specific to TGF-β. Our results are consistent with a model in which a strong Notch signal indirectly deregulates c-Myc expression and thereby renders Mv1Lu epithelial cells resistant to growth-inhibitory signals.