RESUMO
BACKGROUND: Regulation of gene transcription in response to stress is central to a cell's ability to cope with environmental challenges. Taf14 is a YEATS domain protein in S.cerevisiae that physically associates with several transcriptionally relevant multisubunit complexes including the general transcription factors TFIID and TFIIF and the chromatin-modifying complexes SWI/SNF, INO80, RSC and NuA3. TAF14 deletion strains are sensitive to a variety of stresses suggesting that it plays a role in the transcriptional stress response. RESULTS: In this report we survey published genome-wide transcriptome and occupancy data to define regulatory properties associated with Taf14-dependent genes. Our transcriptome analysis reveals that stress related, TATA-containing and SAGA-dependent genes were much more affected by TAF14 deletion than were TFIID-dependent genes. Comparison of Taf14 and multiple transcription factor occupancy at promoters genome-wide identified a group of proteins whose occupancy correlates with that of Taf14 and whose proximity to Taf14 suggests functional interactions. We show that Taf14-repressed genes tend to be extensively regulated, positively by SAGA complex and the stress dependent activators, Msn2/4 and negatively by a wide number of repressors that act upon promoter chromatin and TBP. CONCLUSIONS: Taken together our analyses suggest a novel role for Taf14 in repression and derepression of stress induced genes, most probably as part of a regulatory network which includes Cyc8-Tup1, Srb10 and histone modifying enzymes.
Assuntos
Regulação Fúngica da Expressão Gênica , Proteínas de Saccharomyces cerevisiae/metabolismo , Fator de Transcrição TFIID/metabolismo , Perfilação da Expressão Gênica , Genômica , Resposta ao Choque Térmico/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/fisiologiaRESUMO
The yeast transcriptional activator Gal4 has long been the prototype for studies of eukaryotic transcription. Gal4 is phosphorylated in the DNA-binding domain (DBD); however, the molecular details and functional significance of this remain unknown. We mutagenized seven potential phosphoserines that lie on the solvent-exposed face of the DBD structure and assessed them for transcriptional activity and DNA binding in vivo. Serine to alanine mutants at positions 22, 47, and 85 show the greatest reduction in promoter occupancy and transcriptional activity at the MEL1 promoter containing a single UASGAL . Substitutions with the phosphomimetic aspartate restored DNA-binding and transcriptional activity at serines 22 and 85, suggesting that they are potential sites of Gal4 phosphorylation in vivo. In contrast, the serine to alanine mutants, except serine 22, were fully proficient for binding to the GAL1-10 promoter, containing multiple UASGAL sites, although they had a reduced ability to activate transcription. Collectively, these data show that at the GAL1-10 promoter, functions of the DBD in transcriptional activation can be uncoupled from roles in promoter binding. We suggest that the serines in the DBD mediate protein-protein contacts with the transcription machinery, leading to stabilization of Gal4 at promoters.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Regiões Promotoras Genéticas , Domínios e Motivos de Interação entre Proteínas/fisiologia , Serina/metabolismo , Ativação Transcricional , Sequência de Aminoácidos , Sítios de Ligação , Proteínas de Ligação a DNA/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Análise Serial de Proteínas , Conformação Proteica , Solventes , Leveduras/genética , Leveduras/metabolismoRESUMO
Identification of multiple histone acylations diversifies transcriptional control by metabolism, but their functions are incompletely defined. Here we report evidence of histone crotonylation in the human fungal pathogen Candida albicans. We define the enzymes that regulate crotonylation and show its dynamic control by environmental signals: carbon sources, the short-chain fatty acids butyrate and crotonate, and cell wall stress. Crotonate regulates stress-responsive transcription and rescues C. albicans from cell wall stress, indicating broad impact on cell biology. The YEATS domain crotonylation readers Taf14 and Yaf9 are required for C. albicans virulence, and Taf14 controls gene expression, stress resistance, and invasive growth via its chromatin reader function. Blocking the Taf14 C terminus with a tag reduced virulence, suggesting that inhibiting Taf14 interactions with chromatin regulators impairs function. Our findings shed light on the regulation of histone crotonylation and the functions of the YEATS proteins in eukaryotic pathogen biology and fungal infections.
Assuntos
Candida albicans/metabolismo , Proteínas Fúngicas/metabolismo , Histonas/metabolismo , Animais , Candida albicans/patogenicidade , Cromatina/metabolismo , Crotonatos/metabolismo , Feminino , Histona Acetiltransferases/metabolismo , Humanos , Camundongos , Domínios Proteicos , Fator de Transcrição TFIID , VirulênciaRESUMO
Telomeres are dynamic chromosome-end structures that serve as guardians of genome stability. They are known to be one of the major determinants of aging and longevity in higher mammals. Studies have demonstrated a direct correlation between telomere length and life expectancy, stress, DNA damage, and onset of aging-related diseases. This review discusses the most important factors that influence our telomeres. Various genetic and environmental factors such as diet, physical activity, obesity, and stress are known to influence health and longevity as well as telomere dynamics. Individuals currently have the opportunity to modulate the dynamics of their aging and health span, monitor these processes, and even make future projections by following their telomere dynamics. As telomeres react to positive as well as negative health factors, we should be able to directly influence our telomere metabolism, slow their deterioration, and diminish our aging and perhaps extend our life and health span.
Assuntos
Envelhecimento/genética , Expectativa de Vida , Longevidade/genética , Estado Nutricional , Telômero/genética , Animais , Senescência Celular/genética , Exercício Físico/fisiologia , HumanosRESUMO
The yeast protein Xtc1 was identified as a protein that binds directly and specifically to the activation domains of acidic activators such as E2F-1, Gal4 and VP16. Additionally, it was shown to co-purify with the RNA polymerase II holoenzyme complex and it was suggested that Xtc1 functions as a regulator of transcription that modulates the response of RNA polymerase II to transcriptional activators. We have further analyzed the transcription function of Xtc1 and show that its fusion to a heterologous DNA binding domain can repress transcription of a reporter gene in vivo in an Srb10/11-dependent manner. We suggest that the presence of Xtc1 in the RNA polymerase II holoenzyme could help to recruit an Srb10-active form of the holoenzyme to target promoters. This same protein has also been implicated in mitochondrial DNA recombination, maintenance and repair. Determination of the subcellular localization using a GFP-Xtc1 fusion shows that it localizes to both the nucleus and the mitochondria in vivo, which is consistent with Xtc1 having a function in both cellular compartments.
Assuntos
Regulação Fúngica da Expressão Gênica , Proteínas Nucleares , Proteínas Repressoras/metabolismo , Saccharomyces cerevisiae , Fatores de Transcrição/metabolismo , Transcrição Gênica , Núcleo Celular/química , Núcleo Celular/metabolismo , Quinase 8 Dependente de Ciclina , Quinases Ciclina-Dependentes/genética , Quinases Ciclina-Dependentes/metabolismo , Ciclinas/genética , Ciclinas/metabolismo , Genes Reporter , Holoenzimas/química , Holoenzimas/metabolismo , Mitocôndrias/química , Mitocôndrias/metabolismo , Regiões Promotoras Genéticas/genética , Estrutura Terciária de Proteína , Transporte Proteico , RNA Polimerase II/química , RNA Polimerase II/metabolismo , Proteínas Repressoras/química , Proteínas Repressoras/genética , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Fatores de Transcrição/química , Fatores de Transcrição/genéticaRESUMO
In bacteria, the RecA protein forms recombinogenic filaments required for the SOS response and DNA recombination. In order to form a recombinogenic filament, wild type RecA needs to bind ATP and to interact with mediator proteins. The RecA730 protein is a mutant version of RecA with superior catalytic abilities, allowing filament formation without the help of mediator proteins. The mechanism of RecA730 filament formation is not well understood, and the question remains as to whether the RecA730 protein requires ATP binding in order to become competent for filament formation. We examined two mutants, recA730,4159 (presumed to be defective for ATP binding) and recA730,2201 (defective for ATP hydrolysis), and show that they have different properties with respect to SOS induction, conjugational recombination and double-strand break repair. We show that ATP binding is essential for all RecA730 functions, while ATP hydrolysis is required only for double-strand break repair. Our results emphasize the similarity of the SOS response and conjugational recombination, neither of which requires ATP hydrolysis by RecA730.
Assuntos
Escherichia coli/enzimologia , Escherichia coli/fisiologia , Proteínas Mutantes/metabolismo , Recombinases Rec A/metabolismo , Recombinação Genética , Resposta SOS em Genética , Trifosfato de Adenosina/metabolismo , Reparo do DNA , Escherichia coli/genética , Proteínas Mutantes/genética , Ligação Proteica , Multimerização Proteica , Recombinases Rec A/genéticaRESUMO
Mitochondrial dysfunction has been shown to elicit broad effects on nuclear gene expression. We show here that transcription dependent on the prototypical acidic activator Gal4 is responsive to mitochondrial dysfunction. In cells with no mitochondrial DNA, Gal4-dependent gene expression is elevated. A minimal Gal4 activator containing the DNA binding and activation domain is sufficient for this response. Transcription dependent on a fusion of Gal4 to a heterologous DNA binding domain is similarly elevated in a mitochondrial mutant. Analysis of different Gal4-dependent promoters and gel mobility shift assays suggest that the effect of mitochondrial dysfunction on Gal4 activity is related to increased DNA binding to the cognate Gal4 element. Given that fermentation is the only means to obtain energy in respiratory deficient cells, it is possible that higher Gal4 activity in cells with dysfunctional mitochondria works to promote more efficient fermentation of galactose.
Assuntos
Mitocôndrias/metabolismo , Mitocôndrias/patologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Fatores de Transcrição/metabolismo , Ativação Transcricional/genética , DNA Bacteriano/metabolismo , Proteínas de Ligação a DNA , Fermentação , Galactose/metabolismo , Regulação Fúngica da Expressão Gênica , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Transcrição Gênica , Regulação para CimaRESUMO
Three cyclin dependent kinases, Cdk7, Cdk8 and Cdk9 are intimately connected with the processes of RNA polymerase II dependent transcription initiation and elongation in eukaryotic cells. Each of these kinases is part of a larger multisubunit complex, TFIIH, Mediator and p-TEFb respectively. Of the three kinases, Cdk8 is the most complex given that it has been associated with both positive and negative effects on transcription via mechanisms that include regulation of transcription factor turnover, regulation of CTD phosphorylation and regulation of activator or repressor function. Furthermore, Cdk8 has emerged as a key regulator of multiple transcriptional programs linked to nutrient/growth factor sensing and differentiation control. As such Cdk8 represents a potentially interesting therapeutic drug target. In this review we summarize the current state of knowledge on Cdk8 function both in yeast and higher eukaryotes as well as discussing the effects of Cdk8 null mutations at the organismal level.
Assuntos
Quinase 8 Dependente de Ciclina/genética , Regulação da Expressão Gênica , Schizosaccharomyces/genética , Transcrição Gênica , Animais , Quinase 8 Dependente de Ciclina/metabolismo , Humanos , Mutação , Fosforilação , Estrutura Terciária de Proteína , Schizosaccharomyces/metabolismo , Transdução de Sinais , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Escherichia coli responds to nutrient exhaustion by entering a state commonly referred to as the stationary phase. Cells entering the stationary phase redirect metabolic circuits to scavenge any available nutrients and become resistant to different stresses. However, many DNA repair pathways are downregulated in stationary-phase cells, which results in increased mutation rates. DNA repair activity generally depends on consumption of energy and often requires de novo proteins synthesis. Consequently, unless stringently regulated during stationary phase, DNA repair activities may lead to an irreversible depletion of energy sources and, therefore to cell death. Most stationary phase morphological and physiological modifications are regulated by an alternative RNA polymerase sigma factor RpoS. However, nutrient availability, and the frequency and nature of stresses, are different in distinct environmental niches, which impose conflicting choices that result in selection of the loss or of the modification of RpoS function. Consequently, DNA repair activity, which is partially controlled by RpoS, is differently modulated in different environments. This results in the variable mutation rates among different E. coli ecotypes. Hence, the polymorphism of mutation rates in natural E. coli populations can be viewed as a byproduct of the selection for improved fitness.
Assuntos
Reparo do DNA , Escherichia coli/genética , Estresse Oxidativo/genética , Adaptação Biológica/genética , Proteínas de Bactérias/genética , Metabolismo Energético , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Fator sigma/genéticaRESUMO
During the past two decades, the yeast Gal4 protein has been used as a model for studying transcriptional activation in eukaryotes. Many of the properties of transcriptional regulation first demonstrated for Gal4 have since been shown to be reiterated in the function of several other eukaryotic transcriptional regulators. Technological advances based on the transcriptional properties of this factor--such as the two-hybrid technology and Gal4-inducible systems for controlled gene expression--have had far-reaching influences in fields beyond transcription. In this review, we provide an updated account of Gal4 function, including data from new technologies that have been recently applied to the study of the GAL network.
Assuntos
Proteínas de Ligação a DNA/genética , Regulação Fúngica da Expressão Gênica/fisiologia , Modelos Moleculares , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Fatores de Transcrição/genética , Transcrição Gênica/fisiologia , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/fisiologia , Saccharomyces cerevisiae/fisiologia , Proteínas de Saccharomyces cerevisiae/biossíntese , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/fisiologia , Fatores de Transcrição/biossíntese , Fatores de Transcrição/metabolismo , Fatores de Transcrição/fisiologia , Ativação Transcricional/fisiologiaRESUMO
The retinoblastoma family of proteins are key cell cycle regulatory molecules important for the differentiation of various mammalian cell types. The retinoblastoma protein regulates transcription of a variety of genes either by blocking the activation domain of various activators or by active repression via recruitment to appropriate promoters. We show here that the retinoblastoma family of proteins functions as direct transcriptional repressors in a heterologous yeast system when fused to the DNA binding domain of Gal4. Mapping experiments indicate that either the A or the B domain of the pocket region is sufficient for repression in vivo. As is the case in mammalian cells, a phosphorylation site mutant of the retinoblastoma protein is a stronger transcriptional repressor than the wild type protein. We show that transcriptional repression by pRb is dependent on CLN3 in vivo. Furthermore, the yeast histone deacetylase components, RPD3 and SIN3, are required for transcriptional repression.