RESUMO
A significant seasonal correlation was recently shown for brown recluse spider activity. Vetter (2011) observed brown recluse spiders were submitted by the general public predominantly during April-October. For patients with suspected brown recluse spider bites (BRSB), we have observed the same seasonality. Among 45 cases with features consistent of a BRSB, 43 (95.6%) occurred during April-October. Both the Vetter study and our study serve to demonstrate seasonal activity for brown recluse spiders.
Assuntos
Estações do Ano , Picada de Aranha , Animais , HumanosRESUMO
The structure of an intermediate in the initiation to elongation transition of Escherichia coli RNA polymerase has been visualized through region-specific DNA cleavage by the hydroxyl radical reagent FeBABE. FeBABE was tethered to specific sites of the final sigma(70) subunit and incorporated into two specialized paused elongation complexes that obligatorily retain the final sigma(70) initiation subunit and are targets for modification by lambdoid phage late gene antiterminators. The FeBABE cleavage pattern reveals structures similar to open complex, except for notable changes to region 3 of final sigma(70) that might reflect the presence of stably bound transcript. Binding of the antiterminator protein Q displaces the reactivity of FeBABE conjugated to region 4 of final sigma(70), suggesting that final sigma(70) subunit rearrangement is a step in conversion of RNAP to the antiterminating form.
Assuntos
Bacteriófago lambda/metabolismo , RNA Polimerases Dirigidas por DNA/genética , Fatores de Alongamento de Peptídeos/metabolismo , Proteínas Virais/metabolismo , Bacteriófago lambda/genética , Sequência de Bases , DNA Viral , Dados de Sequência Molecular , Regiões Promotoras GenéticasRESUMO
Gre proteins of prokaryotes, and SII proteins of eukaryotes and archaea, are transcription elongation factors that promote an endogenous transcript cleavage activity of RNA polymerases; this process promotes elongation through obstructive regions of DNA, including transcription pauses that act as sites of genetic regulation. We show that a regulatory pause in the early part of the late gene operon of bacteriophage lambda is subject to such cleavage and resynthesis. In cells lacking the cleavage factors GreA and GreB, the pause is prolonged, and RNA polymerase occupies a variant position at the pause site. Furthermore, GreA and GreB are required to mediate efficient function of the lambda gene Q antiterminator at this site. Thus, cleavage factors are necessary for the natural progression of RNA polymerase in vivo.
Assuntos
Proteínas de Bactérias/metabolismo , Bacteriófago lambda/genética , RNA Polimerases Dirigidas por DNA/metabolismo , Proteínas de Escherichia coli , Regulação Viral da Expressão Gênica , Fatores de Transcrição/metabolismo , Transcrição Gênica/genética , Proteínas de Bactérias/genética , Sequência de Bases , Pegada de DNA , RNA Polimerases Dirigidas por DNA/genética , Escherichia coli/enzimologia , Escherichia coli/genética , Escherichia coli/virologia , Genes Virais/genética , Cinética , Modelos Genéticos , Dados de Sequência Molecular , Mutação/genética , Nucleotídeos/metabolismo , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Sequências Reguladoras de Ácido Nucleico/genética , Fatores de Transcrição/genética , Fatores de Elongação da Transcrição , Proteínas Virais/genética , Proteínas Virais/metabolismoRESUMO
The sigma subunit of eubacterial RNA polymerase is required throughout initiation, but how it communicates with core polymerase (alpha(2)betabeta') is poorly understood. The present work addresses the location and function of the interface of sigma with core. Our studies suggest that this interface is extensive as mutations in six conserved regions of sigma(70) hinder the ability of sigma to bind core. Direct binding of one of these regions to core can be demonstrated using a peptide-based approach. The same regions, and even equivalent residues, in sigma(32) and sigma(70) alter core interaction, suggesting that sigma(70) family members use homologous residues, at least in part, to interact with core. Finally, the regions of sigma that we identify perform specialized functions, suggesting that different portions of the interface perform discrete roles during transcription initiation.
Assuntos
Proteínas de Bactérias/química , RNA Polimerases Dirigidas por DNA/química , Proteínas de Choque Térmico/química , RNA Polimerase I/química , Fator sigma/química , Fatores de Transcrição/química , Transcrição Gênica , Sequência de Aminoácidos , Substituição de Aminoácidos , Proteínas de Bactérias/metabolismo , Sítios de Ligação , RNA Polimerases Dirigidas por DNA/genética , RNA Polimerases Dirigidas por DNA/metabolismo , Escherichia coli/enzimologia , Escherichia coli/genética , Proteínas de Choque Térmico/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Ligação Proteica , Conformação Proteica , RNA Polimerase I/metabolismo , Proteínas Recombinantes de Fusão/química , Fator sigma/genética , Fator sigma/metabolismo , Fatores de Transcrição/metabolismoRESUMO
The sigma initiation factor sigma70 of Escherichia coli acts not only in promoter recognition and DNA strand opening, but also to mediate the transformation of RNA polymerase (RNAP) to an antiterminating form by the phage lambda gene Q protein. Q is able to bind and modify RNAP when alpha70, still present in the initially elongating enzyme, recognizes a repeat of the -10 promoter element and induces a transcription pause. We have isolated mutations in the rpoD gene for sigma70 that impair Q function because they reduce the ability of sigma70 to recognize the downstream pause site. These mutations identify a locus of sigma70 that is important for the formation and stability of open promoter complex, likely because it mediates protein interactions with RNAP core.
Assuntos
Bacteriófago lambda/genética , RNA Polimerases Dirigidas por DNA/genética , RNA Polimerases Dirigidas por DNA/fisiologia , Terminação Traducional da Cadeia Peptídica/genética , Regiões Promotoras Genéticas , Fator sigma/genética , Fator sigma/fisiologia , Proteínas Virais/metabolismo , Substituição de Aminoácidos/genética , Asparagina/genética , Ácido Aspártico/genética , Bacteriófago lambda/crescimento & desenvolvimento , Sequência de Bases , RNA Polimerases Dirigidas por DNA/metabolismo , Escherichia coli/enzimologia , Escherichia coli/genética , Leucina/genética , Substâncias Macromoleculares , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese , Fenilalanina/genética , Ligação Proteica/genética , Fator sigma/metabolismo , Transcrição GênicaRESUMO
In transcription initiation, the DNA strands must be separated to expose the template to RNA polymerase. As the closed initiation complex is converted to an open one, specific protein-DNA interactions involving bases of the nontemplate strand form and stabilize the promoter complex in the region of unwinding. Specific interaction between RNA polymerase and the promoter in Escherichia coli was detected and quantified as the binding affinity of nontemplate oligonucleotide sequences. The RNA polymerase subunit sigma factor 70 contacted the bases of the nontemplate DNA strand through its conserved region 2; a mutation that affected promoter function altered the binding affinity of the oligonucleotide to the enzyme.
