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Efeito da S-nitrosilação sobre a estrutura de PtpA, e clonagem e caracterização inicial de PtkA e SapM de Mycobacterium tuberculosis

Matiollo, Camila
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Dissertação de Mestrado Formato: 115 p.| il., grafs., tabs.
POR
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biolólogicas, Programa de Pós-Graduação em Bioquímica, Florianópolis, 2012; A S-nitrosilação de PtpA de Mycobacterium tuberculosis diminui sua atividade fosfatase. O objetivo deste trabalho é investigar o efeito da S-nitrosilação nos parâmetros cinéticos e na estabilidade térmica de PtpA. Por meio de ensaios de biotin switch observou-se que a substituição do resíduo Cys53 por um resíduo de alanina em mutantes resultou em proteínas incapazes de se ligar a biotina após tratamento com doador de NO. Observou-se também que a KM da PtpA nitrosilada foi semelhante à sua forma não modificada, mas a Vmax foi reduzida pela metade. Em contraste, a mutante C53A tratada com GSNO mostrou KM e Vmax semelhantes à forma não tratada. Na desnaturação térmica de PtpA S-nitrosilada, a TM diminuiu consideravelmente na proteína selvagem, C11A e C16A, porém as mutantes C53A, C11A/C53A e C16A/C53A não tiveram mudanças significativas. Esses resultados sugerem que a S-nitrosilação ocorre especificamente na C53 não catalítica, essa alteração não afeta a afinidade pelo substrato e a S-nitrosilação da Cys53 afeta a estabilidade térmica da proteína. Por outro lado...

"Fator de transcrição AtMYB30 de Arabidopsis thaliana

Botelho, Carolina Pereira Tavares
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Tese de Doutorado Formato: 129 p.| il., grafs.
POR
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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Bioquímica, Florianópolis, 2014.; As proteínas MYB constituem uma importante família de fatores de transcrição e desempenham, em plantas, funções regulatórias no desenvolvimento e nas respostas de defesa. Exemplo importante desta família é a proteína AtMYB30 de Arabidopsis thaliana que está envolvida no início da morte celular, durante o processo de resposta de hipersensibilidade e respostas de defesa vegetal. No processo de sinalização celular, o óxido nítrico pode regular a ligação das proteínas MYB ao DNA de diversas maneiras, entre elas através da S-nitrosilação. Dessa forma, o objetivo deste trabalho foi caracterizar e avaliar a ocorrência da modificação pós-traducional S-nitrosilação no fator de transcrição AtMYB30 de Arabidopsis thaliana, sua interação com o DNA e o efeito estrutural destes fatores. Mutagênese sítio-dirigida foi usada para obter os mutantes C49A, C53A e C49AC53A. O domínio de ligação ao DNA de AtMYB30 foi capaz de ligar-se ao DNA na forma ativa, assim como os seus simples mutantes em cisteína, o que não ocorreu com o duplo mutante, comprovando a importância destes aminoácidos altamente reativo na formação do complexo. Além disso...

Tendência da incidência de câncer do colo do útero invasor em quatro capitais brasileiras: dados dos registros de câncer de base populacional, 1990-2004

Ayres,Andréia Rodrigues Gonçalves; Silva,Gulnar Azevedo e; Guimarães,Raphael Mendonça
Fonte: Instituto de Estudos em Saúde Coletiva da Universidade Federal do Rio de Janeiro Publicador: Instituto de Estudos em Saúde Coletiva da Universidade Federal do Rio de Janeiro
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2013 PT
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Os Registros de Câncer de Base Populacional (RCBP) coletam sistematicamente dados de serviços de diagnóstico e tratamento de pacientes por câncer, fornecendo assim dados de incidência de câncer. No Brasil, os primeiros RCBP surgiram em Recife e São Paulo na década de 1960, e atualmente existem 28 distribuídos entre capitais e demais cidades pelo país. O objetivo do estudo é Analisar a tendência das taxas de incidência do câncer do colo do útero com base nos dados de RCBP selecionados. Foram acessados os dados disponibilizados no site do Instituto Nacional de Câncer (INCA) dos RCBP de Fortaleza, Porto Alegre, Recife e São Paulo, para obtenção do número de casos para neoplasia maligna do colo do útero, neoplasia do útero porção não especificada e carcinoma in situ do colo do útero por idade. Foram utilizados os denominadores populacionais informados pelo Ministério da Saúde (Datasus). Foram calculadas as taxas específicas por idade para os grupos etários estratificados de 25 a 34, 35 a 49 e 50 a 59 anos. A tendência foi analisada por regressão polinomial. Os períodos com informações disponíveis de 1990 a 2004 variaram de 7 a 13 anos. A análise gráfica mostrou menor regularidade para Recife. A tendência de incidência para o câncer do colo do útero foi declinante e pode ser...

Effects of Salmonella typhimurium Infection and Ofloxacin Treatment on Glucose and Glutamine Metabolism in Caco-2/TC-7 Cells

Posho, Leta; Delbos-Bocage, Laurence; Gueylard, Delphine; Farinotti, Robert; Carbon, Claude
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/1998 EN
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The effects of both Salmonella typhimurium infection and 5 mM ofloxacin treatment on 2 mM glutamine and 5 mM glucose metabolism in the enterocyte-like Caco-2/TC-7 cell line were studied. These cells utilized glutamine (212.07 ± 16.75 [mean ± standard deviation] nmol per h per 106 viable cells) and, to a lesser extent, glucose (139.63 ± 11.52 nmol per h per 106 viable cells). Metabolism of these substrates in Caco-2/TC-7 cells resembled that in rat, pig, or human enterocytes. Infection by S. typhimurium C53-enhanced glucose and glutamine substrate utilization by 32 and 22%, respectively and enhanced glucose and glutamine substrate oxidation by eight- and twofold, respectively. These increases in glucose and glutamine metabolism (especially glucose metabolism) were due in part to the metabolism of intracellular bacteria and/or to the activation of cellular metabolism. Substrate metabolism (especially glucose metabolism) in C53-infected cells was partially reduced by treatment with ofloxacin. It was concluded that cellular fuel metabolism is stimulated at the earliest stage of infection (3 to 4 h) and that treatment with 5 mM ofloxacin does not completely restore substrate metabolism to the levels observed in uninfected cells, possibly because this treatment does not eradicate intracellular S. typhimurium completely.

Characterization of Human RNA Polymerase III Identifies Orthologues for Saccharomyces cerevisiae RNA Polymerase III Subunits

Hu, Ping; Wu, Si; Sun, Yuling; Yuan, Chih-Chi; Kobayashi, Ryuji; Myers, Michael P.; Hernandez, Nouria
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2002 EN
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Unlike Saccharomyces cerevisiae RNA polymerase III, human RNA polymerase III has not been entirely characterized. Orthologues of the yeast RNA polymerase III subunits C128 and C37 remain unidentified, and for many of the other subunits, the available information is limited to database sequences with various degrees of similarity to the yeast subunits. We have purified an RNA polymerase III complex and identified its components. We found that two RNA polymerase III subunits, referred to as RPC8 and RPC9, displayed sequence similarity to the RNA polymerase II RPB7 and RPB4 subunits, respectively. RPC8 and RPC9 associated with each other, paralleling the association of the RNA polymerase II subunits, and were thus paralogues of RPB7 and RPB4. Furthermore, the complex contained a prominent 80-kDa polypeptide, which we called RPC5 and which corresponded to the human orthologue of the yeast C37 subunit despite limited sequence similarity. RPC5 associated with RPC53, the human orthologue of S. cerevisiae C53, paralleling the association of the S. cerevisiae C37 and C53 subunits, and was required for transcription from the type 2 VAI and type 3 human U6 promoters. Our results provide a characterization of human RNA polymerase III and show that the RPC5 subunit is essential for transcription.

RPC53 encodes a subunit of Saccharomyces cerevisiae RNA polymerase C (III) whose inactivation leads to a predominantly G1 arrest.

Mann, C; Micouin, J Y; Chiannilkulchai, N; Treich, I; Buhler, J M; Sentenac, A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1992 EN
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RPC53 is shown to be an essential gene encoding the C53 subunit specifically associated with yeast RNA polymerase C (III). Temperature-sensitive rpc53 mutants were generated and showed a rapid inhibition of tRNA synthesis after transfer to the restrictive temperature. Unexpectedly, the rpc53 mutants preferentially arrested their cell division in the G1 phase as large, round, unbudded cells. The RPC53 DNA sequence is predicted to code for a hydrophilic M(r)-46,916 protein enriched in charged amino acid residues. The carboxy-terminal 136 amino acids of C53 are significantly similar (25% identical amino acid residues) to the same region of the human BN51 protein. The BN51 cDNA was originally isolated by its ability to complement a temperature-sensitive hamster cell mutant that undergoes a G1 cell division arrest, as is true for the rpc53 mutants.

A subcomplex of RNA polymerase III subunits involved in transcription termination and reinitiation

Landrieux, Emilie; Alic, Nazif; Ducrot, Cécile; Acker, Joël; Riva, Michel; Carles, Christophe
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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While initiation of transcription by RNA polymerase III (Pol III) has been thoroughly investigated, molecular mechanisms driving transcription termination remain poorly understood. Here we describe how the characterization of the in vitro transcriptional properties of a Pol III variant (Pol IIIΔ), lacking the C11, C37, and C53 subunits, revealed crucial information about the mechanisms of Pol III termination and reinitiation. The specific requirement for the C37–C53 complex in terminator recognition was determined. This complex was demonstrated to slow down elongation by the enzyme, adding to the evidence implicating the elongation rate as a critical determinant of correct terminator recognition. In addition, the presence of the C37–C53 complex required the simultaneous addition of C11 to Pol IIIΔ for the enzyme to reinitiate after the first round of transcription, thus uncovering a role for polymerase subunits in the facilitated recycling process. Interestingly, we demonstrated that the role of C11 in recycling was independent of its role in RNA cleavage. The data presented allowed us to propose a model of Pol III termination and its links to reinitiation.

A tumor suppressor C53 protein antagonizes checkpoint kinases to promote cyclin-dependent kinase 1 activation

Jiang, Hai; Wu, Jianchun; He, Chen; Yang, Wending; Li, Honglin
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/2009 EN
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Cyclin dependent kinase 1 (Cdk1)/cyclin B1 complex is the driving force for mitotic entry, and its activation is tightly regulated by the G2/M checkpoint. We originally reported that a novel protein C53 (also known as Cdk5rap3 and LZAP) potentiates DNA damage-induced cell death by modulating the G2/M checkpoint (1). More recently, Wang et al (2007) found that C53/LZAP may function as a tumor suppressor via inhibiting NF-κB signaling (2). We report here identification of C53 protein as a novel regulator of Cdk1 activation. We found that knockdown of C53 protein causes delayed Cdk1 activation and mitotic entry. During DNA damage response, activation of checkpoint kinase 1 and 2 (Chk1 and Chk2) is partially inhibited by C53 overexrepsssion. Intriguingly, we found that C53 interacts with checkpoint kinase 1 (Chk1) and antagonizes its function. Moreover, a portion of C53 protein is localized at the centrosome, and centrosome-targeting C53 potently promotes local Cdk1 activation. Taken together, our results strongly suggest that C53 is a novel negative regulator of checkpoint response. By counteracting Chk1, C53 promotes Cdk1 activation and mitotic entry in both unperturbed cell cycle progression and DNA damage response.

The C53/C37 Subcomplex of RNA Polymerase III Lies Near the Active Site and Participates in Promoter Opening*

Kassavetis, George A.; Prakash, Prachee; Shim, Eunjung
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
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The C53 and C37 subunits of RNA polymerase III (pol III) form a subassembly that is required for efficient termination; pol III lacking this subcomplex displays increased processivity of RNA chain elongation. We show that the C53/C37 subcomplex additionally plays a role in formation of the initiation-ready open promoter complex similar to that of the Brf1 N-terminal zinc ribbon domain. In the absence of C53 and C37, the transcription bubble fails to stably propagate to and beyond the transcriptional start site even when the DNA template is supercoiled. The C53/C37 subcomplex also stimulates the formation of an artificially assembled elongation complex from its component DNA and RNA strands. Protein-RNA and protein-DNA photochemical cross-linking analysis places a segment of C53 close to the RNA 3′ end and transcribed DNA strand at the catalytic center of the pol III elongation complex. We discuss the implications of these findings for the mechanism of transcriptional termination by pol III and propose a structural as well as functional correspondence between the C53/C37 subcomplex and the RNA polymerase II initiation factor TFIIF.

A zinc-binding site by negative selection induces metallodrug susceptibility in an essential chaperonin

Cun, Shujian; Sun, Hongzhe
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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GroES is an indispensable chaperonin virtually found throughout all life forms. Consequently, mutations of this protein must be critically scrutinized by natural selection. Nevertheless, the homolog from a potentially virulent gastric pathogen, Helicobacter pylori, strikingly features a histidine/cysteine-rich C terminus that shares no significant homology with other family members. Additionally, three more (H45, C51, and C53) are uniquely present in its apical domain. The statistical analyses show that these residues may have originated from negative selection, presumably driven by either dependent or independent amino acid mutations. In the absence of the C-terminal metal-binding domain, the mutant protein still exhibits a substantial capacity for zinc binding in vivo. The biochemical properties of site-directed mutants indicate that H45, C51, and C53 make up an oxidation-sensitive zinc-binding site that may donate the bound metal to a zinc acceptor. Of interest, bismuth antiulcer drugs strongly bind at this site (Kd of approximately 7 × 10-26 M), replacing the bound zinc and consequently inducing the disruption of the quaternary structure. Because biological features by negative selection are usually inert to change during evolution...

A Novel C53/LZAP-interacting Protein Regulates Stability of C53/LZAP and DDRGK Domain-containing Protein 1 (DDRGK1) and Modulates NF-κB Signaling*

Wu, Jianchun; Lei, Guohua; Mei, Mei; Tang, Yi; Li, Honglin
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
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28.17%
C53/LZAP (also named as Cdk5rap3) is a putative tumor suppressor that plays important roles in multiple cell signaling pathways, including DNA damage response and NF-κB signaling. Yet how its function is regulated remains largely unclear. Here we report the isolation and characterization of two novel C53/LZAP-interacting proteins, RCAD (Regulator of C53/LZAP and DDRGK1) and DDRGK1 (DDRGK domain-containing protein 1). Our co-immunoprecipitation assays confirmed their interactions, while gel filtration assay indicated that C53/LZAP and RCAD may form a large protein complex. Intriguingly, we found that RCAD knockdown led to dramatic reduction of C53/LZAP and DDRGK1 proteins. We also found that C53/LZAP and DDRGK1 became more susceptible to the proteasome-mediated degradation in RCAD knockdown cells, whereas their ubiquitination was significantly attenuated by RCAD overexpression. In addition, we found that RCAD, like C53/LZAP, also plays an important role in regulation of NF-κB signaling and cell invasion. Taken together...

Transcriptional Regulation of the Ufm1 Conjugation System in Response to Disturbance of the Endoplasmic Reticulum Homeostasis and Inhibition of Vesicle Trafficking

Zhang, Yinghua; Zhang, Mingsheng; Wu, Jianchun; Lei, Guohua; Li, Honglin
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 13/11/2012 EN
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Homeostasis of the endoplasmic reticulum (ER) is essential for normal cellular functions. Disturbance of this homeostasis causes ER stress and activates the Unfolded Protein Response (UPR). The Ufm1 conjugation system is a novel Ubiquitin-like (Ubl) system whose physiological target(s) and biological functions remain largely undefined. Genetic study has demonstrated that the Ufm1-activating enzyme Uba5 is indispensible for erythroid differentiation in mice, highlighting the importance of this novel system in animal development. In this report we present the evidence for involvement of RCAD/Ufl1, a putative Ufm1-specific E3 ligase, and its binding partner C53/LZAP protein in ufmylation of endogenous Ufm1 targets. Moreover, we found that the Ufm1 system was transcriptionally up-regulated by disturbance of the ER homeostasis and inhibition of vesicle trafficking. Using luciferase reporter and ChIP assays, we dissected the Ufm1 promoter and found that Ufm1 was a potential target of Xbp-1, one of crucial transcription factors in UPR. We further examined the effect of Xbp-1 deficiency on the expression of the Ufm1 components. Interestingly, the expression of Ufm1, Uba5, RCAD/Ufl1 and C53/LZAP in wild-type mouse embryonic fibroblasts (MEFs) was significantly induced by inhibition of vesicle trafficking...

Transcription termination by the eukaryotic RNA polymerase III

Arimbasseri, Aneeshkumar G.; Rijal, Keshab; Maraia, Richard J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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RNA polymerase (pol) III transcribes a multitude of tRNA and 5S rRNA genes as well as other small RNA genes distributed through the genome. By being sequence-specific, precise and efficient, transcription termination by pol III not only defines the 3′ end of the nascent RNA which directs subsequent association with the stabilizing La protein, it also prevents transcription into downstream DNA and promotes efficient recycling. Each of the RNA polymerases appears to have evolved unique mechanisms to initiate the process of termination in response to different types of termination signals. However, in eukaryotes much less is known about the final stage of termination, destabilization of the elongation complex with release of the RNA and DNA from the polymerase active center. By comparison to pols I & II, pol III exhibits the most direct coupling of the initial and final stages of termination, both of which occur at a short oligo(dT) tract on the non-template strand (dA on the template) of the DNA. While pol III termination is autonomous involving the core subunits C2 and probably C1, it also involves subunits C11, C37 and C53, which act on the pol III catalytic center and exhibit homology to the pol II elongation factor TFIIS, and TFIIFα/β respectively. Here we compile knowledge of pol III termination and associate mutations that affect this process with structural elements of the polymerase that illustrate the importance of C53/37 both at its docking site on the pol III lobe and in the active center. The models suggest that some of these features may apply to the other eukaryotic pols.

RNA polymerase III mutants in TFIIFα-like C37 that cause terminator readthrough with no decrease in transcription output

Rijal, Keshab; Maraia, Richard J.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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How eukaryotic RNA polymerases switch from elongation to termination is unknown. Pol III subunits Rpc53 and Rpc37 (C53/37) form a heterodimer homologous to TFIIFβ/α. C53/37 promotes efficient termination and together with C11 also mediates pol III recycling in vitro. We previously developed Schizosaccharomyces pombe strains that report on two pol III termination activities: RNA oligo(U) 3′-end cleavage, and terminator readthrough. We randomly mutagenized C53 and C37 and isolated many C37 mutants with terminator readthrough but no comparable C53 mutants. The majority of C37 mutants have strong phenotypes with up to 40% readthrough and map to a C-terminal tract previously localized near Rpc2p in the pol III active center while a minority represent a distinct class with weaker phenotype, less readthrough and 3′-oligo(U) lengthening. Nascent pre-tRNAs released from a terminator by C37 mutants have shorter 3′-oligo(U) tracts than in cleavage-deficient C11 double mutants indicating RNA 3′-end cleavage during termination. We asked whether termination deficiency affects transcription output in the mutants in vivo both by monitoring intron-containing nascent transcript levels and 14C-uridine incorporation. Surprisingly, multiple termination mutants have no decrease in transcript output relative to controls. These data are discussed in context of current models of pol III transcription.

Distinguishing Core and Holoenzyme Mechanisms of Transcription Termination by RNA Polymerase III

Arimbasseri, Aneeshkumar G.; Maraia, Richard J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2013 EN
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Transcription termination by RNA polymerase (Pol) III serves multiple purposes; it delimits interference with downstream genes, forms 3′ oligo(U) binding sites for the posttranscriptional processing factor, La protein, and resets the polymerase complex for reinitiation. Although an interplay of several Pol III subunits is known to collectively control these activities, how they affect molecular function of the active center during termination is incompletely understood. We have approached this using immobilized Pol III-nucleic acid scaffolds to examine the two major components of termination, transcription pausing and RNA release. This allowed us to distinguish two mechanisms of termination by isolated Saccharomyces cerevisiae Pol III. A core mechanism can operate in the absence of C53/37 and C11 subunits but requires synthesis of 8 or more 3′ U nucleotides, apparently reflecting inherent sensitivity to an oligo(rU·dA) hybrid that is the termination signal proper. The holoenzyme mechanism requires fewer U nucleotides but uses C53/37 and C11 to slow elongation and prevent terminator arrest. N-terminal truncation of C53 or point mutations that disable the cleavage activity of C11 impair their antiarrest activities. The data are consistent with a model in which C53...

Caspase-mediated cleavage of C53/LZAP protein causes abnormal microtubule bundling and rupture of the nuclear envelope

Wu, Jianchun; Jiang, Hai; Luo, Shouqing; Zhang, Mingsheng; Zhang, Yinghua; Sun, Fei; Huang, Shuang; Li, Honglin
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
EN
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27.86%
Apoptotic nucleus undergoes distinct morphological and biochemical changes including nuclear shrinkage, chromatin condensation and DNA fragmentation, which are attributed to caspase-mediated cleavage of several nuclear substrates such as lamins. As most of active caspases reside in the cytoplasm, disruption of the nuclear-cytoplasmic barrier is essential for caspases to reach their nuclear targets. The prevailing proposed mechanism is that the increase in the permeability of nuclear pores induced by caspases allows the caspases and other apoptotic factors to diffuse into the nucleus, thereby resulting in the nuclear destruction. Here, we report a novel observation that physical rupture of the nuclear envelope (NE) occurs in the early stage of apoptosis. We found that the NE rupture was caused by caspase-mediated cleavage of C53/LZAP, a protein that has been implicated in various signaling pathways, including NF-κB signaling and DNA damage response, as well as tumorigenesis and metastasis. We also demonstrated that C53/LZAP bound indirectly to the microtubule (MT), and expression of the C53/LZAP cleavage product caused abnormal MT bundling and NE rupture. Taken together, our findings suggest a novel role of C53/LZAP in the regulation of MT dynamics and NE structure during apoptotic cell death. Our study may provide an additional mechanism for disruption of the nuclear-cytoplasmic barrier during apoptosis.

Subunit compositions of Arabidopsis RNA polymerases I and III reveal Pol I- and Pol III-specific forms of the AC40 subunit and alternative forms of the C53 subunit

Ream, Thomas S.; Haag, Jeremy R.; Pontvianne, Frederic; Nicora, Carrie D.; Norbeck, Angela D.; Paša-Tolić, Ljiljana; Pikaard, Craig S.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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27.22%
Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA polymerases I and III (abbreviated as Pol I and Pol III), the first analysis of their physical compositions in plants. In all eukaryotes examined to date, AC40 and AC19 subunits are common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes. Surprisingly, A. thaliana and related species express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Pol III. Changes at eight amino acid positions correlate with the functional divergence of Pol I- and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit and either protein can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the 12 subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers.

Statistical Inference for Computable General Equilibrium Models with Application to a Model of the Moroccan Economy

ABDELKHALEK, Touhami; DUFOUR, Jean-Marie
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 212801 bytes; application/pdf
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We study the problem of measuring the uncertainty of CGE (or RBC)-type model simulations associated with parameter uncertainty. We describe two approaches for building confidence sets on model endogenous variables. The first one uses a standard Wald-type statistic. The second approach assumes that a confidence set (sampling or Bayesian) is available for the free parameters, from which confidence sets are derived by a projection technique. The latter has two advantages: first, confidence set validity is not affected by model nonlinearities; second, we can easily build simultaneous confidence intervals for an unlimited number of variables. We study conditions under which these confidence sets take the form of intervals and show they can be implemented using standard methods for solving CGE models. We present an application to a CGE model of the Moroccan economy to study the effects of policy-induced increases of transfers from Moroccan expatriates.; Nous étudions le problème de la mesure de l’incertitude des simulations de modèles d’équilibre général calculable (MEGC). Nous décrivons deux approches pour construire des régions de confiance pour les variables endogènes de ces modèles. La première utilise une statistique standard de type Wald. La seconde approche suppose l’existence...

Semi-Parametric Weak Instrument Regressions with an Application to the Risk-Return Trade-off

PERRON, Benoit
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 2337970 bytes; application/pdf
Relevância na Pesquisa
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Recent work shows that a low correlation between the instruments and the included variables leads to serious inference problems. We extend the local-to-zero analysis of models with weak instruments to models with estimated instruments and regressors and with higher-order dependence between instruments and disturbances. This makes this framework applicable to linear models with expectation variables that are estimated non-parametrically. Two examples of such models are the risk-return trade-off in finance and the impact of inflation uncertainty on real economic activity. Results show that inference based on Lagrange Multiplier (LM) tests is more robust to weak instruments than Wald-based inference. Using LM confidence intervals leads us to conclude that no statistically significant risk premium is present in returns on the S&P 500 index, excess holding yields between 6-month and 3-month Treasury bills, or in yen-dollar spot returns.; Des recherches récentes démontrent qu'une corrélation faible entre les instruments et les variables explicatives peut mener à de sérieux problèmes d'inférence dans les régressions avec variables instrumentales. Nous étendons l'analyse locale à zéro des modèles avec instruments faibles aux modèles avec des instruments et régresseurs estimés et avec de la dépendance dans les moments supérieurs. Ainsi...

Rooting of apical, intermediate and basal minicuttings in clones of Eucalyptus benthamii; ENRAIZAMENTO DE MINIESTACAS APICAIS, INTERMEDIÁRIAS E BASAIS EM CLONES DE Eucalyptus benthamii

Benin, Cristiane Carla; Universidade Estadual do Centro- Oeste; Peres, Fabiana Schmidt Bandeira; Universidade Estadual do Centro- Oeste; Garcia, Flávio Augusto de Oliveira; Universidade Estadual do Centro- Oeste
Fonte: FUPEF DO PARANÁ Publicador: FUPEF DO PARANÁ
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 13/09/2013 POR
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This study aimed to evaluate the rooting of apical, intermediate and basal ministumps of Eucalyptus benthamii Maiden et Cambage. The minicuttings were collected from ministumps originated from seedlings. The experiment was conducted in a completely randomized design, in a 4x3 factorial arrangement with factors consisting of four clones of E. benthamii (C50, C51, C52 e C53) and three types of cuttings (apical, intermediate and basal). The survival and rooting were evaluated with 45 days  in shadow house, and 90 days in the full sun stage. In the end of the evaluations, the clone C52 proved to be better in survival, rooting and height growth. In full sun stage, when the seedlings completed the development cycle, the apical minicutting proved to be the kind of propagules with grater aptitude on rooting when compared with the others clones.; Este trabalho teve como objetivo avaliar o enraizamento de miniestacas apicais, intermediárias e basais de Eucalyptus benthamii Maiden et Cambage. As miniestacas utilizadas foram coletadas de minicepas estabelecidas a partir de mudas de origem seminal. O experimento foi conduzido no delineamento inteiramente casualizado, em arranjo fatorial 4x3, sendo os fatores constituídos por quatro clones de E. benthamii (C50...