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Modelagem de ensaios não destrutivos por ultra-som utilizando o método dos elementos finitos. ; Modeling of ultrasonic non destructive evaluation using FEM.

San Miguel Medina, Jimmy Ernesto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/12/2005 Português
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Os modelos existentes de propagação de ondas de ultra-som em meios líquidos e sólidos consideram a geração e recepção das ondas produzidas por transdutores simulados segundo o modelo do pistão plano ou com excitações cuja amplitude varia radialmente no pistão. Esses modelos são simplificados e não explicam completamente o comportamento real de transdutores de ultra-som interagindo com líquidos e sólidos. As verificações experimentais de propagação da onda de ultra-som em meios líquidos mostram que a onda de borda é diferente da onda plana. Observa-se também a existência de outras ondas não previstas nos modelos anteriores. Essas ondas são conhecidas como ondas head. A utilização do método dos elementos finitos (MEF) para a modelagem de propagação de ondas de ultra-som, incluindo o transdutor piezelétrico, permite a obtenção de resultados realísticos, conseguindo assim descrever com maior precisão o comportamento do transdutor e das ondas de ultra-som se propagando em diferentes meios e interagindo com defeitos que se comportam como refletores. Apesar disso, os resultados desses modelos dependem das características precisas dos materiais que compõem o transdutor. O transdutor de ultra-som é composto por uma cerâmica piezelétrica...

Acoplamento MEC-MEF para análise de pórtico linear sobre base elástica; Coupling BEM/FEM to linear frames analysis on elastic foundation

Luiz Antonio dos Reis
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/05/2014 Português
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O presente trabalho está divido em quatro partes. Na primeira parte, utilizando o método dos elementos de contorno (MEC), se fez a análise de problemas bidimensionais com aproximação linear. Foi considerada a possibilidade de se aplicar a técnica de sub-regiões para se levar em conta a diversidade de materiais, bem como a suavização do contorno por mínimos quadrados para evitar a possíveis perturbações. Foi considerado a possibilidade de colocação de uma linha de carga no domínio. Na segunda parte, utilizando o método dos elementos finitos (MEF), se fez a análise linear de pórticos planos. Para este estudo foram utilizadas barras com dois nós e esses com três graus de liberdade. Na terceira parte, a análise elástica linear de meios contínuos (Estado Plano de Tensão Generalizado) enrijecidos com elementos lineares (barras) é estudada fazendo-se um acoplamento entre elementos modelados com o MEC e com o MEF. As fibras são modeladas pelo MEF com elementos lineares de três graus de liberdade por nó e quatro nós por barra. Os elementos planos são modelados pelo MEC com elementos isoparamétricos lineares no perímetro. É permitido o uso de sub-regiões com objetivo de generalizar o tratamento do meio elástico. Na quarta parte...

Effects of moderate electric fields (MEF) on denaturation of whey proteins solutions

Pereira, Ricardo; Teixeira, J. A.; Vicente, A. A.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 Português
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Electric fields application during thermal processing are now receiving increased attention due to uniform heating of liquids and extremely rapid heating rates, which presumably enables higher temperatures to be applied without inducing excessive denaturation of the constituent proteins [1]. The aim of this work was to evaluate the effects of moderate electric fields (MEF) on denaturation kinetics and thermodynamic properties of whey protein dispersions at temperatures ranging from 75 to 90 ºC. Application of MEF led to a lower denaturation of whey proteins, kinetically traduced by lower values of reaction order (n) and rate constant (k) (p < 0.05), when compared to those from conventional heating under equivalent heating rates and holding times. Furthermore, the application MEF combined with short come-up times has reduced considerably the denaturation of proteins during early stages of heating (>30% of native soluble protein than conventional heating). In general, denaturation reactions during MEF were less dependent on temperature increase presenting higher values of ΔG# in the range of temperatures studied. Further, MEF produced smaller changes (p < 0.05) in whey protein aggregates’ size when compared with a conventional heating MEF offers the potential to change the functional and technological properties of whey proteins...

Functional and Physical Interactions between AML1 Proteins and an ETS Protein, MEF: Implications for the Pathogenesis of t(8;21)-Positive Leukemias

Mao, Shifeng; Frank, Richard C.; Zhang, Jin; Miyazaki, Yasushi; Nimer, Stephen D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/1999 Português
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The AML1 and ETS families of transcription factors play critical roles in hematopoiesis; AML1, and its non-DNA-binding heterodimer partner CBFβ, are essential for the development of definitive hematopoiesis in mice, whereas the absence of certain ETS proteins creates specific defects in lymphopoiesis or myelopoiesis. The promoter activities of numerous genes expressed in hematopoietic cells are regulated by AML1 proteins or ETS proteins. MEF (for myeloid ELF-1-like factor) is a recently cloned ETS family member that, like AML1B, can strongly transactivate several of these promoters, which led us to examine whether MEF functionally or physically interacts with AML1 proteins. In this study, we demonstrate direct interactions between MEF and AML1 proteins, including the AML1/ETO fusion protein, in t(8;21)-positive acute myeloid leukemia (AML) cells. Using mutational analysis, we identified a novel ETS-interacting subdomain (EID) in the C-terminal portion of the Runt homology domain (RHD) in AML1 proteins and determined that the N-terminal region of MEF was responsible for its interaction with AML1. MEF and AML1B synergistically transactivated an interleukin 3 promoter reporter gene construct, yet the activating activity of MEF was abolished when MEF was coexpressed with AML1/ETO. The repression by AML1/ETO was independent of DNA binding but depended on its ability to interact with MEF...

Association of JC Virus Large T Antigen with Myelin Basic Protein Transcription Factor (MEF-1/Purα) in Hypomyelinated Brains of Mice Transgenically Expressing T Antigen

Tretiakova, Anna; Otte, Jessica; Croul, Sidney E.; Kim, Julie H.; Johnson, Edward M.; Amini, Shohreh; Khalili, Kamel
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/1999 Português
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Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease caused by cytolytic destruction of oligodendrocytes, the myelin-producing cells of the central nervous system, by the human neurotropic JC virus (JCV). The early protein of JCV, T antigen, which is produced at the early stage of infection, is important for orchestrating the events leading to viral lytic infection and cytolytic destruction of oligodendrocytes. Results from transgenic mouse studies, however, have revealed that, in the absence of lytic infection, this protein can induce brain hypomyelination and suppression of myelin gene expression. Since expression of the gene encoding myelin basic protein, the major component of myelin, can be regulated by a DNA-binding transcription factor, MEF-1/Purα, (Purα), we have examined the level of this protein in transgenic mouse brains. Results from immunoprecipitation and Western blots showed that while there was no drastic decrease in the level of MEF-1/Purα in transgenic mouse brains, JCV T antigen was found in a complex with MEF-1/Purα. Immunohistological studies revealed abnormal oligodendrocytes in white matter, where MEF-1/Purα and T antigen were detected. Furthermore, immunogold electron microscopic studies revealed that Purα and T antigen are colocalized in the nucleus of the oligodendrocytes and in hippocampal neurons. Interestingly...

Distribution of mef(A) in Gram-Positive Bacteria from Healthy Portuguese Children

Luna, Vicki A.; Heiken, Marc; Judge, Kathleen; Ulep, Catherine; Van Kirk, Nicole; Luis, Henrique; Bernardo, Mario; Leitao, Jose; Roberts, Marilyn C.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2002 Português
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We screened 615 gram-positive isolates from 150 healthy children for the presence of the erm(A), erm(B), erm(C), erm(F), and mef(A) genes. The mef(A) genes were found in 20 (9%) of the macrolide-resistant isolates, including Enterococcus spp., Staphylococcus spp., and Streptococcus spp. Sixteen of the 19 gram-positive isolates tested carried the other seven open reading frames (ORFs) described in Tn1207.1, a genetic element carrying mef(A) recently described in Streptococcus pneumoniae. The three Staphylococcus spp. did not carry orf1 to orf3. A gram-negative Acinetobacter junii isolate also carried the other seven ORFs described in Tn1207.1. A Staphylococcus aureus isolate, a Streptococcus intermedius isolate, a Streptococcus sp. isolate, and an Enterococcus sp. isolate had their mef(A) genes completely sequenced and showed 100% identity at the DNA and amino acid levels with the mef(A) gene from S. pneumoniae.

Pharmacodynamic Modeling of Clarithromycin against Macrolide-Resistant [PCR-Positive mef(A) or erm(B)] Streptococcus pneumoniae Simulating Clinically Achievable Serum and Epithelial Lining Fluid Free-Drug Concentrations

Noreddin, Ayman M.; Roberts, Danielle; Nichol, Kim; Wierzbowski, Aleksandra; Hoban, Daryl J.; Zhanel, George G.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2002 Português
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The association between macrolide resistance mechanisms and clinical outcomes remains understudied. The present study, using an in vitro pharmacodynamic model, assessed clarithromycin (CLR) activity against mef(A)-positive and erm(B)-negative Streptococcus pneumoniae isolates by simulating free-drug concentrations in serum and both total (protein-bound and free) and free drug in epithelial lining fluid (ELF). Five mef(A)-positive and erm(B)-negative strains, one mef(A)-negative and erm(B)-positive strain, and a control [mef(A)-negative and erm(B)-negative] strain of S. pneumoniae were tested. CLR was modeled using a one-compartment model, simulating a dosage of 500 mg, per os, twice a day (in serum, free-drug Cp maximum of 2 μg/ml, t1/2 of 6 h; in ELF, CELF(total) maximum of 35μg/ml, t1/2 of 6 h; CELF(free) maximum of 14 μg/ml, t1/2 of 6 h). Starting inocula were 106 CFU/ml in Mueller-Hinton broth with 2% lysed horse blood. With sampling at 0, 4, 8, 12, 20, and 24 h, the extent of bacterial killing was assessed. Achieving CLR T/MIC values of ≥90% (AUC0-24/MIC ratio, ≥61) resulted in bacterial eradication, while T>MIC values of 40 to 56% (AUC0-24/MIC ratios of ≥30.5 to 38) resulted in a 1.2 to 2.0 log10 CFU/ml decrease at 24 h compared to that for the initial inoculum. CLR T/MIC values of ≤8% (AUC0-24/MIC ratio...

A muscle-specific enhancer within intron 1 of the human dystrophin gene is functionally dependent on single MEF-1/E box and MEF-2/AT-rich sequence motifs.

Klamut, H J; Bosnoyan-Collins, L O; Worton, R G; Ray, P N
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/04/1997 Português
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In previous studies we have described a 5.0 kb Hin dIII fragment downstream of muscle exon 1 that exhibits properties consistent with a muscle-specific transcriptional enhancer. The goal of this study has been to identify the sequence elements responsible for muscle-specific enhancer activity. Functional studies indicated that this enhancer is active in pre- and post-differentiated H9C2(2-1) myoblasts but functions poorly in L6 and C2C12 myotubes. The core enhancer region was delimited to a 195 bp Spe I- Acc I fragment and sequence analysis identified three MEF-1/E box and two MEF-2/AT-rich motifs as potential muscle-specific regulatory domains. EMSA competition and DNase footprinting indicated that sequences within a 30 bp region containing single adjoining MEF-1/E box and MEF-2/AT-rich motifs are target binding sites for trans -acting factors expressed in H9C2(2-1) myotubes but not in L6 or C2C12 myotubes. Site-specific mutations within these motifs resulted in a significant reduction in enhancer activity in H9C2(2-1) myotubes. These results suggest that the mechanisms governing DMD gene expression in muscle are similar to those identified in other muscle-specific genes. However, the myogenic profile of enhancer activity and trans -acting factor binding suggests a more specialized role for this enhancer that is consistent with its potential involvement in dystrophin gene regulation in cardiac muscle.

Presence of the tet(O) Gene in Erythromycin- and Tetracycline-Resistant Strains of Streptococcus pyogenes and Linkage with either the mef(A) or the erm(A) Gene

Giovanetti, Eleonora; Brenciani, Andrea; Lupidi, Remo; Roberts, Marilyn C.; Varaldo, Pietro E.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2003 Português
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Sixty-three recent Italian clinical isolates of Streptococcus pyogenes resistant to both erythromycin (MICs ≥ 1 μg/ml) and tetracycline (MICs ≥ 8 μg/ml) were genotyped for macrolide and tetracycline resistance genes. We found 19 isolates carrying the mef(A) and the tet(O) genes; 25 isolates carrying the erm(A) and tet(O) genes; and 2 isolates carrying the erm(A), tet(M), and tet(O) genes. The resistance of all erm(A)-containing isolates was inducible, but the isolates could be divided into two groups on the basis of erythromycin MICs of either >128 or 1 to 4 μg/ml. The remaining 17 isolates included 15 isolates carrying the erm(B) gene and 2 isolates carrying both the erm(B) and the mef(A) genes, with all 17 carrying the tet(M) gene. Of these, 12 carried Tn916-Tn1545-like conjugative transposons. Conjugal transfer experiments demonstrated that the tet(O) gene moved with and without the erm(A) gene and with the mef(A) gene. These studies, together with the results of pulsed-field gel electrophoresis experiments and hybridization assays with DNA probes specific for the tet(O), erm(A), and mef(A) genes, suggested a linkage of tet(O) with either erm(A) or mef(A) in erythromycin- and tetracycline-resistant S. pyogenes isolates. By amplification and sequencing experiments...

A new serum-responsive, cardiac tissue-specific transcription factor that recognizes the MEF-2 site in the myosin light chain-2 promoter.

Zhou, M D; Goswami, S K; Martin, M E; Siddiqui, M A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1993 Português
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We have identified a serum-responsive, cardiac tissue-specific transcription factor, BBF-1, that recognizes an AT-rich sequence (element B), identical to the myocyte enhancer factor (MEF-2) target site, in the cardiac myosin light chain-2 (MLC-2) promoter. Deletion of the element B sequence alone from the cardiac MLC-2 promoter causes, as does that of the MEF-2 site from other promoters and the enhancer of skeletal muscle genes, a marked reduction of transcription. BBF-1 is distinguishable from cardiac MEF-2 on the basis of immunoprecipitation with an antibody which recognizes MEF-2 but not BBF-1. Unlike MEF-2, BBF-1 is present exclusively in nuclear extracts from cardiac muscle cells cultured in a medium containing a high concentration of serum. Removal of serum from culture medium abolishes BBF-1 activity selectively with a concomitant loss of the positive regulatory effect of element B on MLC-2 gene transcription, indicating that there is a correlation between the BBF-1 binding activity and the tissue-specific role of the element B (MEF-2 site) sequence. The loss of element B-mediated activation of transcription is reversed following the refeeding of cells with serum-containing medium. These data demonstrate that cardiac muscle cells contain two distinct protein factors...

A novel, tissue-restricted zinc finger protein (HF-1b) binds to the cardiac regulatory element (HF-1b/MEF-2) in the rat myosin light-chain 2 gene.

Zhu, H; Nguyen, V T; Brown, A B; Pourhosseini, A; Garcia, A V; van Bilsen, M; Chien, K R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1993 Português
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The AT-rich element MEF-2 plays an important role in the maintenance of the muscle-specific expression of a number of cardiac and skeletal muscle genes. In the MLC-2 gene, an AT-rich element (HF-1b) which contains a consensus MEF-2 site is required for cardiac tissue-specific expression. The present study reports the isolation and characterization of a cDNA which encodes a novel C2H2 zinc finger (HF-1b) that binds in a sequence-specific manner to the HF-1b/MEF-2 site in the MLC-2 promoter. A number of independent criteria suggest that this HF-1b zinc finger protein is a component of the endogenous HF-1b/MEF-2 binding activity in cardiac muscle cells and that it can serve as a transcriptional activator of the MLC-2 promoter in transient assays. These studies suggest that, in addition to the previously reported RSRF proteins, structurally divergent transcriptional factors can bind to MEF-2-like sites in muscle promoters. These results underscore the complexity of the regulation of the muscle gene program via these AT-rich elements in cardiac and skeletal muscle.

A single MEF-2 site is a major positive regulatory element required for transcription of the muscle-specific subunit of the human phosphoglycerate mutase gene in skeletal and cardiac muscle cells.

Nakatsuji, Y; Hidaka, K; Tsujino, S; Yamamoto, Y; Mukai, T; Yanagihara, T; Kishimoto, T; Sakoda, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1992 Português
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In order to analyze the transcriptional regulation of the muscle-specific subunit of the human phosphoglycerate mutase (PGAM-M) gene, chimeric genes composed of the upstream region of the PGAM-M gene and the bacterial chloramphenicol acetyltransferase (CAT) gene were constructed and transfected into C2C12 skeletal myocytes, primary cultured cardiac muscle cells, and C3H10T1/2 fibroblasts. The expression of chimeric reporter genes was restricted in skeletal and cardiac muscle cells. In C2C12 myotubes and primary cultured cardiac muscle cells, the segment between nucleotides -165 and +41 relative to the transcription initiation site was sufficient to confer maximal CAT activity. This region contains two E boxes and one MEF-2 motif. Deletion and substitution mutation analysis showed that a single MEF-2 motif but not the E boxes had a substantial effect on skeletal and cardiac muscle-specific enhancer activity and that the cardiac muscle-specific negative regulatory region was located between nucleotides -505 and -165. When the PGAM-M gene constructs were cotransfected with MyoD into C3H10T1/2, the profile of CAT activity was similar to that observed in C2C12 myotubes. Gel mobility shift analysis revealed that when the nuclear extracts from skeletal and cardiac muscle cells were used...

The MEF-3 motif is required for MEF-2-mediated skeletal muscle-specific induction of the rat aldolase A gene.

Hidaka, K; Yamamoto, I; Arai, Y; Mukai, T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1993 Português
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The rat aldolase A gene contains two alternative promoters and two alternative first exons. The distal promoter M is expressed at a high level only in skeletal muscle. Previous in vitro transfection studies identified the region from -202 to -85 as an enhancer that is responsible for dramatic activation during the differentiation of chicken primary myoblasts. This enhancer contains an A/T-rich sequence resembling the MEF-2 motif, which is an important element of muscle enhancers and promoters. In this study, we demonstrate that the MEF-2 sequence is essential but not sufficient for the activity of the enhancer. Another region required for the activity was recognized by a nuclear factor, tentatively named MAF1. MAF1 was found in both muscle cells and nonmuscle cells, and MAF1 from both cell types was indistinguishable by gel retardation and DNase I footprint experiments. The sequence required for MAF1 binding is very similar to the MEF-3 motif, which is an element of the skeletal muscle-specific enhancer of the cardiac troponin C gene. Because MAF1 and MEF-3 are closely related in both recognition sequence and distribution, MAF1 and MEF-3 probably represent the same nuclear factor which may play an important role in muscle gene transcription. Thus...

An E box in the desmin promoter cooperates with the E box and MEF-2 sites of a distal enhancer to direct muscle-specific transcription.

Li, H; Capetanaki, Y
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/08/1994 Português
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The first 85 nt upstream of the transcription initiation site of the mouse desmin gene, which contain an E box (E1), the binding site of the helix-loop-helix myogenic regulators, are sufficient to confer low level muscle-specific expression. High levels of desmin expression are due to an enhancer, located between nucleotides -798 and -976, which contains an additional E box (E2) and a muscle-specific enhancer factor-2 (MEF-2) binding site. We have previously shown that both myoD and myogenin can bind to the proximal (E1) and distal (E2) boxes. Here we demonstrate that MEF-2C, a myocyte-restricted member of the MEF-2 family, can bind to the desmin MEF-2 site. Functional units for the enhancer activity required intact E2 and MEF-2 elements. The desmin enhancer can function relatively well with either the E2 box or the MEF-2 site and only mutation of both eliminates transcriptional enhancement; the presence of both of these elements is required for maximum enhancer activity. On the other hand, mutagenesis of just the proximal E1 box showed that this element is essential for desmin gene expression. Double mutations of E1 with E2 or MEF-2 sites suggested that, to achieve high levels of desmin gene expression, E1 serves most possibly as an intermediary for either E2 or MEF-2 enhancer elements to function. The location of the E1 site relative to the TATA box is crucial. Its activity is DNA turn- and distance-dependent. Furthermore...

MEF-2 function is modified by a novel co-repressor, MITR.

Sparrow, D B; Miska, E A; Langley, E; Reynaud-Deonauth, S; Kotecha, S; Towers, N; Spohr, G; Kouzarides, T; Mohun, T J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/09/1999 Português
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The MEF-2 proteins are a family of transcriptional activators that have been detected in a wide variety of cell types. In skeletal muscle cells, MEF-2 proteins interact with members of the MyoD family of transcriptional activators to synergistically activate gene expression. Similar interactions with tissue or lineage-specific cofactors may also underlie MEF-2 function in other cell types. In order to screen for such cofactors, we have used a transcriptionally inactive mutant of Xenopus MEF2D in a yeast two-hybrid screen. This approach has identified a novel protein expressed in the early embryo that binds to XMEF2D and XMEF2A. The MEF-2 interacting transcription repressor (MITR) protein binds to the N-terminal MADS/MEF-2 region of the MEF-2 proteins but does not bind to the related Xenopus MADS protein serum response factor. In the early embryo, MITR expression commences at the neurula stage within the mature somites and is subsequently restricted to the myotomal muscle. In functional assays, MITR negatively regulates MEF-2-dependent transcription and we show that this repression is mediated by direct binding of MITR to the histone deacetylase HDAC1. Thus, we propose that MITR acts as a co-repressor, recruiting a specific deacetylase to downregulate MEF-2 activity.

The ETS Protein MEF Is Regulated by Phosphorylation-Dependent Proteolysis via the Protein-Ubiquitin Ligase SCFSkp2

Liu, Yan; Hedvat, Cyrus V.; Mao, Shifeng; Zhu, Xin-Hua; Yao, Jinjuan; Nguyen, Hoang; Koff, Andrew; Nimer, Stephen D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2006 Português
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MEF is an ETS-related transcription factor with strong transcriptional activating activity that affects hematopoietic stem cell behavior and is required for normal NK cell and NK T-cell development. The MEF (also known as ELF4) gene is repressed by several leukemia-associated fusion transcription factor proteins (PML-retinoic acid receptor α and AML1-ETO), but it is also activated by retroviral insertion in several cancer models. We have previously shown that cyclin A-dependent phosphorylation of MEF largely restricts its activity to the G1 phase of the cell cycle; we now show that MEF is a short-lived protein whose expression level also peaks during late G1 phase. Mutagenesis studies show that the rapid turnover of MEF in S phase is dependent on the specific phosphorylation of threonine 643 and serine 648 at the C terminus of MEF by cdk2 and on the Skp1/Cul1/F-box (SCF) E3 ubiquitin ligase complex SCFSkp2, which targets MEF for ubiquitination and proteolysis. Overexpression of MEF drives cells through the G1/S transition, thereby promoting cell proliferation. The tight regulation of MEF levels during the cell cycle contributes to its effects on regulating cell cycle entry and cell proliferation.

Composite Structure of Streptococcus pneumoniae Containing the Erythromycin Efflux Resistance Gene mef(I) and the Chloramphenicol Resistance Gene catQ▿

Mingoia, Marina; Vecchi, Manuela; Cochetti, Ileana; Tili, Emily; Vitali, Luca A.; Manzin, Aldo; Varaldo, Pietro E.; Montanari, Maria Pia
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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In recent years mef genes, encoding efflux pumps responsible for M-type macrolide resistance, have been investigated extensively for streptococci. mef(I) is a recently described mef variant detected in particular isolates of Streptococcus pneumoniae instead of the more common mef(E) and mef(A). This study shows that mef(I) is located in a new composite genetic element, whose sequence was completely analyzed and the left and right junctions determined, demonstrating a unique genetic organization. The new composite structure (30,505 bp), designated the 5216IQ complex, consists of two halves: a left one (15,316 bp) formed by parts of the known transposons Tn5252 and Tn916, and a right one (15,115 bp) formed by a new fragment, designated the IQ element. While the defective Tn916 contained a silent tet(M) gene, the IQ element, ending with identical transposase genes on both sides and containing the mef(I) gene with an adjacent new msr(D) gene variant and a catQ chloramphenicol acetyltransferase gene, was completely different from the genetic elements carrying other mef genes in pneumococci. This is the first report demonstrating catQ in S. pneumoniae and showing its linkage with a mef gene. Analysis of the chromosomal region beyond the left junction revealed an organization more similar to that of S. pneumoniae strain TIGR4 than to that of strain R6. The 5216IQ complex was apparently nonmobile...

The oncogenic role of the ETS transcription factors MEF and ERG

Sashida, Goro; Bazzoli, Elena; Menendez, Silvia; Liu, Yan; Nimer, Stephen D
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Português
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Several ETS transcription factors, including MEF/ELF4 and ERG, can function as oncogenes and are overexpressed in human cancer. MEF cooperates in tumorigenesis in retroviral insertional mutagenesis-based mouse models of cancer and MEF is overexpressed in human lymphoma and ovarian cancer tissues via unknown mechanisms. ERG (Ets-related gene) overexpression or increased activity has been found in various human cancers, including sarcomas, acute myeloid leukemia and prostate cancer, where the ERG gene is rearranged due to chromosomal translocations. We have been examining how MEF functions as an oncogene and recently showed that MEF can cooperate with H-RasG12V and can inhibit both p53 and p16 expression thereby promoting transformation. In fact, in cells lacking p53, the absence of MEF abrogates H-RasG12V-induced transformation of mouse embryonic fibroblasts, at least in part due to increased p16 expression. We discuss the known mechanisms by which the ETS transcription factors MEF and ERG contribute to the malignant transformation of cells.

The Synergistic Regulatory Effect of Runx2 and MEF Transcription Factors on Osteoblast Differentiation Markers

Lee, Jae-Mok; Cho, Je-Yoel; Libermann, Towia Aron
Fonte: Korean Academy of Periodontology Publicador: Korean Academy of Periodontology
Tipo: Artigo de Revista Científica
Português
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Purpose: Bone tissues for clinical application can be improved by studies on osteoblast differentiation. Runx2 is known to be an important transcription factor for osteoblast differentiation. However, bone morphogenetic protein (BMP)-2 treatment to stimulate Runx2 is not sufficient to acquire enough bone formation in osteoblasts. Therefore, it is necessary to find other regulatory factors which can improve the transcriptional activity of Runx2. The erythroblast transformation-specific (ETS) transcription factor family is reported to be involved in various aspects of cellular proliferation and differentiation. Methods: We have noticed that the promoters of osteoblast differentiation markers such as alkaline phosphatase (Alp), osteopontin (Opn), and osteocalcin (Oc) contain Ets binding sequences which are also close to Runx2 binding elements. Luciferase assays were performed to measure the promoter activities of these osteoblast differentiation markers after the transfection of Runx2, myeloid Elf-1-like factor (MEF), and Runxs+MEF. Reverse-transcription polymerase chain reaction was also done to check the mRNA levels of Opn after Runx2 and MEF transfection into rat osteoblast (ROS) cells. Results: We have found that MEF, an Ets transcription factor...

The steroid receptor coactivator, GRIP-1, is necessary for MEF-2C-dependent gene expression and skeletal muscle differentiation

Chen, Shen Liang; Dowhan, Dennis H.; Hosking, Brett M.; Muscat, George E.O.
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em 15/05/2000 Português
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Nuclear receptor-mediated activation of transcription involves coactivation by cofactors collectively denoted the steroid receptor coactivators (SRCs). The process also involves the subsequent recruitment of p300/CBP and PCAF to a complex that synergistically regulates transcription and remodels the chromatin. PCAF and p300 have also been demonstrated to function as critical coactivators for the muscle-specific basic helix–loop–helix (bHLH) protein MyoD during myogenic commitment. Skeletal muscle differentiation and the activation of muscle-specific gene expression is dependent on the concerted action of another bHLH factor, myogenin, and the MADS protein, MEF-2, which function in a cooperative manner. We examined the functional role of one SRC, GRIP-1, in muscle differentiation, an ideal paradigm for the analysis of the determinative events that govern the cell's decision to divide or differentiate. We observed that the mRNA encoding GRIP-1 is expressed in proliferating myoblasts and post-mitotic differentiated myotubes, and that protein levels increase during differentiation. Exogenous/ectopic expression studies with GRIP-1 sense and antisense vectors in myogenic C2C12 cells demonstrated that this SRC is necessary for (1) induction/activation of myogenin...