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Recent evidence suggests that human gene promoters display gene expression regulatory mechanisms beyond the typical single gene local transcription modulation. In mammalian genomes, genes with an associated bidirectional promoter are abundant; bidirectional promoter architecture serves as a regulatory hub for a gene pair expression. However, it has been suggested that its contribution to transcriptional regulation might exceed local transcription initiation modulation. Despite their abundance, the functional consequences of bidirectional promoter architecture remain largely unexplored. This work studies the long-range gene expression regulatory role of a long non-coding RNA gene promoter using chromosome conformation capture methods. We found that this particular bidirectional promoter contributes to distal gene expression regulation in a target-specific manner by establishing promoter-promoter interactions. In particular, we validated that the promoter-promoter interactions of this regulatory element with the promoter of distal gene BBX contribute to modulating the transcription rate of this gene; removing the bidirectional promoter from its genomic context leads to a rearrangement of BBX promoter-enhancer interactions and to increased gene expression. Moreover, long-range regulatory functionality is not directly dependent on its associated non-coding gene pair expression levels.
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Regulação da Expressão Gênica , Regiões Promotoras Genéticas , RNA Longo não Codificante , Humanos , RNA Longo não Codificante/genética , Regulação da Expressão Gênica/genética , Transcrição Gênica , Elementos Facilitadores GenéticosRESUMO
Objectives: To compare co-expression networks of normal and osteoarthritis knee cartilage to uncover molecules associated with the transcriptional misregulation compromising biological processes (BPs) critical for cartilage homeostasis. Design: Normal and osteoarthritis human knee cartilage RNA-seq GSE114007 dataset was obtained from the Gene Expression Omnibus database. Partial Correlation and Information Theory (PCIT) algorithm was used to build co-expression networks containing all nodes connecting to at least one differentially expressed gene (DEG) in normal and osteoarthritis networks. Hub and hub centrality genes were used to perform functional enrichment analysis. Enriched BPs known to be associated with both healthy and diseased cartilage were compared in depth. Results: Differential co-expression network analyses allowed the identification of DDX43 and USP42 as exclusively co-expressed with DEGs in normal and osteoarthritis networks, respectively. The top hub and hub centrality genes of these networks were HIST1H3A and SNHG12 (normal) and TAF9B and OTUD1 (osteoarthritis). Enrichment analysis revealed several shared BPs between the contrasting groups, which are well-known in osteoarthritis pathogenesis. Protein-protein interaction network analysis for these BPs showed a global down-regulation of transcription factors in osteoarthritis. Specific transcription factors were identified as pleiotropic mediators in articular cartilage maintenance since they take part in several BPs. In addition, chromatin organisation and modification proteins were found relevant for osteoarthritis development. Conclusion: Differential gene co-expression analysis allowed the identification of novel and high priority therapeutic candidate genes that may drive modifications in the transcriptional "status" of cartilage in osteoarthritis.
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Neural induction, both in vivo and in vitro, includes cellular and molecular changes that result in phenotypic specialization related to specific transcriptional patterns. These changes are achieved through the implementation of complex gene regulatory networks. Furthermore, these regulatory networks are influenced by epigenetic mechanisms that drive cell heterogeneity and cell-type specificity, in a controlled and complex manner. Epigenetic marks, such as DNA methylation and histone residue modifications, are highly dynamic and stage-specific during neurogenesis. Genome-wide assessment of these modifications has allowed the identification of distinct non-coding regulatory regions involved in neural cell differentiation, maturation, and plasticity. Enhancers are short DNA regulatory regions that bind transcription factors (TFs) and interact with gene promoters to increase transcriptional activity. They are of special interest in neuroscience because they are enriched in neurons and underlie the cell-type-specificity and dynamic gene expression profiles. Classification of the full epigenomic landscape of neural subtypes is important to better understand gene regulation in brain health and during diseases. Advances in novel next-generation high-throughput sequencing technologies, genome editing, Genome-wide association studies (GWAS), stem cell differentiation, and brain organoids are allowing researchers to study brain development and neurodegenerative diseases with an unprecedented resolution. Herein, we describe important epigenetic mechanisms related to neurogenesis in mammals. We focus on the potential roles of neural enhancers in neurogenesis, cell-fate commitment, and neuronal plasticity. We review recent findings on epigenetic regulatory mechanisms involved in neurogenesis and discuss how sequence variations within enhancers may be associated with genetic risk for neurological and psychiatric disorders.
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Ubiquitous eukaryotic non-coding circular RNAs are involved in numerous co- and post-transcriptional regulatory mechanisms. Recently, we reported full-length intronic circular RNAs (flicRNAs) in Entamoeba histolytica, with 3'ss-5'ss ligation points and 5'ss GU-rich elements essential for their biogenesis and their suggested role in transcription regulation. Here, we explored how flicRNAs impact gene expression regulation. Using CLIP assays, followed by qRT-PCR, we identified that the RabX13 control flicRNA and virulence-associated flicRNAs were bound to the HA-tagged RNA Pol II C-terminus domain in E. histolytica transformants. The U2 snRNA was also present in such complexes, indicating that they belonged to transcription initiation/elongation complexes. Correspondingly, inhibition of the second step of splicing using boric acid reduced flicRNA formation and modified the expression of their parental genes and non-related genes. flicRNAs were also recovered from chromatin immunoprecipitation eluates, indicating that the flicRNA-Pol II complex was formed in the promoter of their cognate genes. Finally, two flicRNAs were found to be cytosolic, whose functions remain to be uncovered. Here, we provide novel evidence of the role of flicRNAs in gene expression regulation in cis, apparently in a widespread fashion, as an element bound to the RNA polymerase II transcription initiation complex, in E. histolytica.
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Mediator 17 (MED17) is a subunit of the Mediator complex that regulates transcription initiation in eukaryotic organisms. In yeast and humans, MED17 also participates in DNA repair, physically interacting with proteins of the nucleotide excision DNA repair system, but this function in plants has not been investigated. We studied the role of MED17 in Arabidopsis plants exposed to UV-B radiation. Our results demonstrate that med17 and OE MED17 plants have altered responses to UV-B, and that MED17 participates in various aspects of the DNA damage response (DDR). Comparison of the med17 transcriptome with that of wild-type (WT) plants showed that almost one-third of transcripts with altered expression in med17 plants were also changed by UV-B exposure in WT plants. Increased sensitivity to DNA damage after UV-B in med17 plants could result from the altered regulation of UV-B responsive transcripts but MED17 also physically interacts with DNA repair proteins, suggesting a direct role of this Mediator subunit during repair. Finally, we show that MED17 is necessary to regulate the DDR activated by ataxia telangiectasia and Rad3 related (ATR), and that programmed cell death 5 (PDCD5) overexpression reverts the deficiencies in DDR shown in med17 mutants. Our data demonstrate that MED17 is an important regulator of DDR after UV-B irradiation in Arabidopsis.
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Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Dano ao DNA , Reparo do DNA/genética , Raios UltravioletaRESUMO
BACKGROUND: Circadian gene expression is essential for organisms to adjust their physiology and anticipate daily changes in the environment. The molecular mechanisms controlling circadian gene transcription are still under investigation. In particular, how chromatin conformation at different genomic scales and regulatory elements impact rhythmic gene expression has been poorly characterized. RESULTS: Here we measure changes in the spatial chromatin conformation in mouse liver using genome-wide and promoter-capture Hi-C alongside daily oscillations in gene transcription. We find topologically associating domains harboring circadian genes that switch assignments between the transcriptionally active and inactive compartment at different hours of the day, while their boundaries stably maintain their structure over time. To study chromatin contacts of promoters at high resolution over time, we apply promoter capture Hi-C. We find circadian gene promoters displayed a maximal number of chromatin contacts at the time of their peak transcriptional output. Furthermore, circadian genes, as well as contacted and transcribed regulatory elements, reach maximal expression at the same timepoints. Anchor sites of circadian gene promoter loops are enriched in DNA binding sites for liver nuclear receptors and other transcription factors, some exclusively present in either rhythmic or stable contacts. Finally, by comparing the interaction profiles between core clock and output circadian genes, we show that core clock interactomes are more dynamic compared to output circadian genes. CONCLUSION: Our results identify chromatin conformation dynamics at different scales that parallel oscillatory gene expression and characterize the repertoire of regulatory elements that control circadian gene transcription through rhythmic or stable chromatin configurations.
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Ritmo Circadiano/genética , Genoma , Regiões Promotoras Genéticas , Animais , Sequência de Bases , Relógios Biológicos/genética , Cromatina/metabolismo , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica , Fígado/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Modelos Genéticos , Fatores de Tempo , Transcrição GênicaRESUMO
Due to their pluripotent nature and unlimited cell renewal, stem cells have been proposed as an ideal material for establishing long-term cnidarian cell cultures. However, the lack of unifying principles associated with "stemness" across the phylum complicates stem cells' identification and isolation. Here, we for the first time report gene expression profiles for cultured coral cells, focusing on regulatory gene networks underlying pluripotency and differentiation. Cultures were initiated from Acropora digitifera tip fragments, the fastest growing tissue in Acropora. Overall, in vitro transcription resembled early larvae, overexpressing orthologs of premetazoan and Hydra stem cell markers, and transcripts with roles in cell division, migration, and differentiation. Our results suggest the presence of pluripotent cell types in cultures and indicate the existence of ancestral genome regulatory modules underlying pluripotency and cell differentiation in cnidaria. Cultured cells appear to be synthesizing protein, differentiating, and proliferating.
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Antozoários/citologia , Antozoários/genética , Animais , Diferenciação Celular , Divisão Celular , Células Cultivadas , Redes Reguladoras de Genes , TranscriptomaRESUMO
WNT signaling pathway regulates several processes involved in the homeostasis of normal cells. Its dysregulation is associated with pathological outcomes like cancer. We previously demonstrated that downregulation of WNT7A correlates with higher proliferation rates in acute lymphoblastic leukemia. However, the regulation of this gene in pathological and normal conditions remains unexplored. In this work, we aimed to analyze the transcriptional regulation of WNT7A in leukemic cells and in normal T lymphocytes after a proliferative stimulus. WNT7A expression was measured in blood cells and in T lymphocytes after phytohemagglutinin-L (PHA-L) treatment or T-cell receptor (TCR) activation by qPCR and Western blot. Promoter methylation was assessed using methylation-sensitive restriction enzymes, and histone modifications were determined by chromatin immunoprecipitation and qPCR. In T-cell acute lymphoblastic leukemia (T-ALL), WNT7A expression is silenced through DNA methylation of CpG island in the promoter region. In normal peripheral blood cells, WNT7A is mainly expressed by monocytes and T lymphocytes. TCR activation induces the downregulation of WNT7A in normal T lymphocytes by changes in histone methylation marks (H3K4me2/3) and histone deacetylases. A proliferative stimulus mediated by IL-2 keeps WNT7A expression at low levels but in the absence of IL-2, the expression of this gene tends to be restored. Furthermore, after TCR activation and WNT7A downregulation, target genes associated with the WNT canonical pathway were upregulated indicating an independent activity of WNT7A from the WNT canonical pathway. WNT7A expression is silenced by long-term DNA methylation in T-ALL-derived cells and downregulated by histone modifications after TCR activation in normal T lymphocytes.
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Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Linfócitos T/imunologia , Proteínas Wnt/metabolismo , Proliferação de Células , Metilação de DNA , Regulação para Baixo , Regulação Neoplásica da Expressão Gênica , Código das Histonas , Humanos , Interleucina-2/metabolismo , Células Jurkat , Ativação Linfocitária , Receptores de Antígenos de Linfócitos T/genética , Proteínas Wnt/genética , Via de Sinalização WntRESUMO
PURPOSE: The molecular mechanism of breast and/or ovarian cancer susceptibility remains unclear in the majority of patients. While germline mutations in the regulatory non-coding regions of BRCA1 and BRCA2 genes have been described, screening has generally been limited to coding regions. The aim of this study was to evaluate the contribution of BRCA1/2 non-coding variants. METHODS: Four BRCA1/2 non-coding regions were screened using high-resolution melting analysis/Sanger sequencing or next-generation sequencing on DNA extracted from index cases with breast and ovarian cancer predisposition (3926 for BRCA1 and 3910 for BRCA2). The impact of a set of variants on BRCA1/2 gene regulation was evaluated by site-directed mutagenesis, transfection, followed by Luciferase gene reporter assay. RESULTS: We identified a total of 117 variants and tested twelve BRCA1 and 8 BRCA2 variants mapping to promoter and intronic regions. We highlighted two neighboring BRCA1 promoter variants (c.-130del; c.-125C > T) and one BRCA2 promoter variants (c.-296C > T) inhibiting significantly the promoter activity. In the functional assays, a regulating region within the intron 12 was found with the same enhancing impact as within the intron 2. Furthermore, the variants c.81-3980A > G and c.4186-2022C > T suppress the positive effect of the introns 2 and 12, respectively, on the BRCA1 promoter activity. We also found some variants inducing the promoter activities. CONCLUSION: In this study, we highlighted some variants among many, modulating negatively the promoter activity of BRCA1 or 2 and thus having a potential impact on the risk of developing cancer. This selection makes it possible to conduct future validation studies on a limited number of variants.
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Proteína BRCA1/genética , Proteína BRCA2/genética , Genes BRCA1 , Genes BRCA2 , Síndrome Hereditária de Câncer de Mama e Ovário/genética , Adulto , Idoso , Estudos de Coortes , Biologia Computacional , Feminino , Predisposição Genética para Doença , Mutação em Linhagem Germinativa , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Íntrons/genética , Pessoa de Meia-Idade , Linhagem , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas/genética , Regiões não Traduzidas/genéticaRESUMO
The COMMD Protein Family is highly conserved among multicellular eukaryotic organisms and many orthologs of human COMMD genes have been found in different species of plants, invertebrates, lower vertebrates, and mammals. COMMD1 is the best characterized member of the family and is conserved among vertebrates. This protein represents a pleiotropic factor involved in the regulation of many cellular and physiological processes that include copper and cholesterol homeostasis, ionic transport, oxidative stress, protein aggregation, protein trafficking, NF-κB-mediated transcription, hypoxia induced transcription, DNA damage response, and oncogenesis. The present work reviews the molecular mechanisms and biological processes regulated by COMMD1 that have been described so far, emphasizing in the regulatory role of the protein and its importance for cellular homeostasis. J. Cell. Biochem. 119: 34-51, 2018. © 2017 Wiley Periodicals, Inc.
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Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Carcinogênese , Hipóxia Celular , Cobre , Reparo do DNA , Regulação da Expressão Gênica , NF-kappa B/metabolismo , Estresse Oxidativo , Agregação Patológica de Proteínas , Transcrição GênicaRESUMO
Cyclin-Dependent Kinase 9 (CDK9) is part of a functional diverse group of enzymes responsible for cell cycle control and progression. It associates mainly with Cyclin T1 and forms the Positive Transcription Elongation Factor b (p-TEFb) complex responsible for regulation of transcription elongation and mRNA maturation. Recent studies have highlighted the importance of CDK9 in many relevant pathologic processes, like cancer, cardiovascular diseases, and viral replication. Herein we provide an overview of the different pathways in which CDK9 is directly and indirectly involved.
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Doenças Cardiovasculares/metabolismo , Quinase 9 Dependente de Ciclina/metabolismo , Proteínas de Neoplasias/metabolismo , Neoplasias/metabolismo , Viroses/metabolismo , Animais , Doenças Cardiovasculares/genética , Ciclina T/genética , Ciclina T/metabolismo , Quinase 9 Dependente de Ciclina/genética , Humanos , Proteínas de Neoplasias/genética , Neoplasias/genética , Fator B de Elongação Transcricional Positiva/genética , Fator B de Elongação Transcricional Positiva/metabolismo , Elongação da Transcrição Genética , Viroses/genéticaRESUMO
Yeast cells can adapt their growth in response to the nutritional environment. Glucose is the favourite carbon source of Saccharomyces cerevisiae, which prefers a fermentative metabolism despite the presence of oxygen. When glucose is consumed, the cell switches to the aerobic metabolism of ethanol, during the so-called diauxic shift. The difference between fermentative and aerobic growth is in part mediated by a regulatory mechanism called glucose repression. During glucose derepression a profound gene transcriptional reprogramming occurs and genes involved in the utilization of alternative carbon sources are expressed. Protein kinase A (PKA) controls different physiological responses following the increment of cAMP as a consequence of a particular stimulus. cAMP-PKA is one of the major pathways involved in the transduction of glucose signalling. In this work the regulation of the promoters of the PKA subunits during respiratory and fermentative metabolism are studied. It is demonstrated that all these promoters are upregulated in the presence of glycerol as carbon source through the Snf1/Cat8 pathway. However, in the presence of glucose as carbon source, the regulation of each PKA promoter subunits is different and only TPK1 is repressed by the complex Hxk2/Mig1 in the presence of active Snf1. Copyright © 2017 John Wiley & Sons, Ltd.
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Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Saccharomyces cerevisiae/enzimologia , Transcrição Gênica/fisiologia , Imunoprecipitação da Cromatina , Proteínas Quinases Dependentes de AMP Cíclico/química , Proteínas Quinases Dependentes de AMP Cíclico/genética , Regulação para Baixo , Fermentação , Glucose/metabolismo , Glicerol/metabolismo , Hexoquinase/genética , Hexoquinase/metabolismo , Fosforilação , Plasmídeos , Regiões Promotoras Genéticas , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , RNA Fúngico/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais/fisiologia , Regulação para Cima , beta-Galactosidase/metabolismoRESUMO
Biological nitrogen fixation (BNF) is a high energy demanding process carried out by diazotrophic microorganisms that supply combined nitrogen to the biosphere. The genes related to BNF are strictly regulated, but these mechanisms are poorly understood in gram-positive bacteria. The transcription factor GlnR was proposed to regulate nitrogen fixation-related genes based on Paenibacillus comparative genomics. In order to validate this proposal, we investigated BNF regulatory sequences in Paenibacillus riograndensis SBR5T genome. We identified GlnR-binding sites flanking σA -binding sites upstream from BNF-related genes. GlnR binding to these sites was demonstrated by surface plasmon resonance spectroscopy. GlnR-DNA affinity is greatly enhanced when GlnR is in complex with feedback-inhibited (glutamine-occupied) glutamine synthetase (GS). GlnR-GS complex formation is also modulated by ATP and AMP. Thereby, gene repression exerted by the GlnR-GS complex is coupled with nitrogen (glutamine levels) and energetic status (ATP and AMP). Finally, we propose a DNA-looping model based on multiple operator sites that represents a strong and strict regulation for these genes.
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Proteínas de Bactérias/genética , Proteínas de Ligação a DNA/genética , Glutamato-Amônia Ligase/genética , Fixação de Nitrogênio/genética , Nitrogênio/metabolismo , Fatores de Transcrição/genética , Sítios de Ligação , Proteínas de Ligação a DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Genoma Bacteriano , Glutamato-Amônia Ligase/metabolismo , Glutamina/metabolismo , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Paenibacillus/genética , Paenibacillus/metabolismo , Regiões Promotoras GenéticasRESUMO
Adipose tissue is a key determinant of whole-body metabolism and energy homeostasis. Unravelling the transcriptional regulatory process during adipogenesis is therefore highly relevant from a biomedical perspective. In these studies, zinc finger protein B-cell lymphoma 6 (Bcl6) was demonstrated to have a role in early adipogenesis of mesenchymal stem cells. Bcl6 is enriched in preadipose versus non-preadipose fibroblasts and shows upregulated expression in the early stage of adipogenesis. Gain- and loss-of-function studies revealed that Bcl6 acts as a key regulator of adipose commitment and differentiation both in vitro and ex vivo RNAi-mediated knockdown of Bcl6 in C3H10T1/2 cells greatly inhibited adipogenic potential, whereas Bcl6 overexpression enhanced adipogenic differentiation. This transcription factor also directly or indirectly targets and controls the expression of some early and late adipogenic regulators (i.e. Zfp423, Zfp467, KLF15, C/EBPδ, C/EBPα and PPARγ). We further identified that Bcl6 transactivated the signal transducers and activators of transcription 1 (STAT1), which was determined as a required factor for adipogenesis. Moreover, overexpression of STAT1 rescued the impairment of adipogenic commitment and differentiation induced by Bcl6 knockdown in C3H10T1/2 cells, thereby confirming that STAT1 is a downstream direct target of Bcl6. This study identifies Bcl6 as a positive transcriptional regulator of early adipose commitment.
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Adipogenia , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Fator de Transcrição STAT1/genética , Células 3T3-L1 , Tecido Adiposo/citologia , Animais , Diferenciação Celular , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Células-Tronco Mesenquimais , Camundongos , Células NIH 3T3 , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas c-bcl-6/genética , Ativação TranscricionalRESUMO
The cAMP-dependent protein kinase (PKA) signaling is a broad pathway that plays important roles in the transduction of environmental signals triggering precise physiological responses. However, how PKA achieves the cAMP-signal transduction specificity is still in study. The regulation of expression of subunits of PKA should contribute to the signal specificity. Saccharomyces cerevisiae PKA holoenzyme contains two catalytic subunits encoded by TPK1, TPK2 and TPK3 genes, and two regulatory subunits encoded by BCY1 gene. We studied the activity of these gene promoters using a fluorescent reporter synthetic genetic array screen, with the goal of systematically identifying novel regulators of expression of PKA subunits. Gene ontology analysis of the identified modulators showed enrichment not only in the category of transcriptional regulators, but also in less expected categories such as lipid and phosphate metabolism. Inositol, choline and phosphate were identified as novel upstream signals that regulate transcription of PKA subunit genes. The results support the role of transcription regulation of PKA subunits in cAMP specificity signaling. Interestingly, known targets of PKA phosphorylation are associated with the identified pathways opening the possibility of a reciprocal regulation. PKA would be coordinating different metabolic pathways and these processes would in turn regulate expression of the kinase subunits.
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Subunidades Catalíticas da Proteína Quinase Dependente de AMP Cíclico/genética , Regulação Fúngica da Expressão Gênica , Regiões Promotoras Genéticas , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Transcrição Gênica , Fusão Gênica Artificial , Subunidades Catalíticas da Proteína Quinase Dependente de AMP Cíclico/metabolismo , Perfilação da Expressão Gênica , Genes Reporter , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Herbaspirillum seropedicae is a diazotrophic bacterium which associates endophytically with economically important gramineae. Flavonoids such as naringenin have been shown to have an effect on the interaction between H. seropedicae and its host plants. We used a high-throughput sequencing based method (RNA-Seq) to access the influence of naringenin on the whole transcriptome profile of H. seropedicae. Three hundred and four genes were downregulated and seventy seven were upregulated by naringenin. Data analysis revealed that genes related to bacterial flagella biosynthesis, chemotaxis and biosynthesis of peptidoglycan were repressed by naringenin. Moreover, genes involved in aromatic metabolism and multidrug transport efllux were actived.
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Lysine is catabolized in developing plant tissues through the saccharopine pathway. In this pathway, lysine is converted into α-aminoadipic semialdehyde (AASA) by the bifunctional enzyme lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH). AASA is then converted into aminoadipic acid (AAA) by aminoadipic semialdehyde dehydrogenase (AASADH). Here, we show that LKR/SDH and AASADH are co-expressed in the sub-aleurone cell layers of the developing endosperm; however, although AASADH protein is produced in reproductive and vegetative tissues, the LKR/SDH protein is detectable only in the developing endosperm. AASADH showed an optimum pH of 7.4 and Kms for AASA and NAD(+) in the micromolar range. In the developing endosperm, the saccharopine pathway is induced by exogenous lysine and repressed by salt stress, whereas proline and pipecolic acid synthesis are significantly repressed by lysine. In young coleoptiles, the LKR/SDH and AASADH transcriptions are induced by abiotic stress, but while the AASADH protein accumulates in the stressed tissues, the LKR/SDH protein is not produced. In the developing seeds, the saccharopine pathway is used for pipecolic acid synthesis although proline may play a major role in abiotic stress response. The results indicate that the saccharopine pathway in maize seed development and stress responses significantly differ from that observed for dicot plants.
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Lisina/metabolismo , Redes e Vias Metabólicas , Zea mays/metabolismo , Aldeídos/metabolismo , Hibridização Genética , Cinética , Modelos Biológicos , Sacaropina Desidrogenases/metabolismo , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/metabolismo , Zea mays/genética , Zea mays/crescimento & desenvolvimentoRESUMO
The core promoter (CP) of the viral genome plays an important role for hepatitis B virus (HBV) replication as it directs initiation of transcription for the synthesis of both the precore and pregenomic (pg) RNAs. The CP consists of the upper regulatory region and the basal core promoter (BCP). The CP overlaps with the 3'-end of the X open reading frames and the 5'-end of the precore region, and contains cis-acting elements that can independently direct transcription of the precore mRNA and pgRNA. Its transcription regulation is under strict control of viral and cellular factors. Even though this regulatory region exhibits high sequence conservation, when variations appear, they may contribute to the persistence of HBV within the host, leading to chronic infection and cirrhosis, and eventually, hepatocellular carcinoma. Among CP sequence variations, those occurring at BCP may dysregulate viral gene expression with emphasis in the hepatitis B e antigen, and contribute to disease progression. In this review these molecular aspects and pathologic topics of core promoter are deeply evaluated.
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Vírus da Hepatite B/genética , Hepatite B/virologia , Regiões Promotoras Genéticas , Proteínas do Core Viral/genética , Animais , Antivirais/uso terapêutico , Carcinoma Hepatocelular/virologia , DNA Viral/biossíntese , Progressão da Doença , Regulação Viral da Expressão Gênica , Variação Genética , Genoma Viral , Genótipo , Hepatite B/complicações , Hepatite B/tratamento farmacológico , Vírus da Hepatite B/efeitos dos fármacos , Vírus da Hepatite B/crescimento & desenvolvimento , Vírus da Hepatite B/patogenicidade , Humanos , Cirrose Hepática/virologia , Neoplasias Hepáticas/virologia , Fenótipo , Transcrição GênicaRESUMO
Protein kinase A (PKA) is a broad specificity protein kinase that controls a physiological response following the increment of cAMP as a consequence of a particular stimulus. The specificity of cAMP-signal transduction is maintained by several levels of control acting all together. Herein we present the study of the regulation of the expression of each PKA subunit, analyzing the activity of their promoters. The promoter of each isoform of TPK and of BCY1 is differentially activated during the growth phase. A negative mechanism of isoform-dependent autoregulation directs TPKs and BCY1 gene expressions. TPK1 promoter activity is positively regulated during heat shock and saline stress. The kinase Rim15, but not the kinase Yak1, positively regulates TPK1 promoter. Msn2/4, Gis1, and Sok2 are transcription factors involved in the regulation of TPK1 expression during stress. TPK2, TPK3, and BCY1 promoters, unlike TPK1, are not activated under stress conditions, although all the promoters are activated under low or null protein kinase A activity. These results indicate that subunits share an inhibitory autoregulatory mechanism but have different mechanisms involved in response to heat shock or saline stress.