RESUMO
Campylobacter gracilis inhabits the gingival sulcus and has been reported to cause various periodontal diseases; it has rarely been reported to cause bacteremia. We describe a case of a two-year-old boy who presented with a consciousness disorder and was transferred to our hospital for treatment of a brain abscess. Magnetic resonance imaging (MRI) showed a 6-cm brain abscess in the right frontal lobe. Urgent drainage and antibiotic administration resulted in a favorable clinical course, and the patient was discharged on the 34th day of hospitalization. Streptococcus anginosus and C. gracilis were identified in the pus. Brain abscesses caused by C. gracilis have rarely been reported, which makes this a valuable case.
RESUMO
The analysis of nucleosome positions and transcription factor binding in chromatin is a central issue for understanding the mechanisms of gene expression in eukaryotes. Here, we have developed a footprinting technique, using multi-cycle primer extension with an infrared-fluorescence DNA sequencer, to analyze chromatin structure in isolated yeast nuclei and transcriptional activator binding in living yeast cells. Using this technique, the binding of the yeast activators Hap1 and Hap2/3/4/5 to their cognate sites was detectable as hypersensitive sites by in vivo UV-photofootprinting, and the locations of nucleosomes in yeast minichromosomes were determined by micrococcal nuclease mapping. We also applied this method to determine the position of the nucleosome in the 5S DNA fragment reconstituted in vitro. This technique allowed us to eliminate the use of radioactive materials and to perform experiments on common benches. Thus, the footprinting procedure established in this study will be useful to researchers studying DNA-protein interactions and chromatin structure in vivo and in vitro.
Assuntos
DNA Fúngico/química , Nucleossomos/química , Pegadas de Proteínas , Transativadores/química , Cromatina/química , Cromatina/genética , Cromossomos Fúngicos/genética , Reparo do DNA/fisiologia , Replicação do DNA/fisiologia , DNA Fúngico/genética , Óperon Lac/genética , Nucleossomos/genética , Plasmídeos/genética , Recombinação Genética , Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Análise de Sequência de DNA , Espectrometria de Fluorescência , Espectrofotometria Infravermelho , Transativadores/genéticaRESUMO
In Saccharomyces cerevisiae, a-cell-specific genes are repressed in MATalpha cells by alpha2/Mcm1, acting in concert with the Ssn6-Tup1 corepressors and the Isw2 chromatin remodeling complex, and nucleosome positioning has been proposed as one mechanism of repression. However, prior studies showed that nucleosome positioning is not essential for repression by alpha2/Mcm1 in artificial reporter plasmids, and the importance of the nucleosome positioning remains questionable. We have tested the function of positioned nucleosomes through alteration of genomic chromatin at the a-cell-specific gene BAR1. We report here that a positioned nucleosome in the BAR1 promoter is disrupted in cis by the insertion of diverse DNA sequences such as poly(dA) . poly(dT) and poly(dC-dG) . poly(dC-dG), leading to inappropriate partial derepression of BAR1. Also, we show that isw2 mutation causes loss of nucleosome positioning in BAR1 in MATalpha cells as well as partial disruption of repression. Thus, nucleosome positioning is required for full repression, but loss of nucleosome positioning is not sufficient to relieve repression completely. Even though disruption of nucleosome positioning by the cis- and trans-acting modulators of chromatin has a modest effect on the level of transcription, it causes significant degradation of the alpha-mating pheromone in MATalpha cells, thereby affecting its cell type identity. Our results illustrate a useful paradigm for analysis of chromatin structural effects at genomic loci.
