RESUMO
Natural competence for DNA uptake is common among bacteria but its evolutionary function is controversial. Resolving the dispute requires a detailed understanding of both how cells decide to take up DNA and how the DNA is processed during and after uptake. We have used whole-genome microarrays to follow changes in gene expression during competence development in wild-type Haemophilus influenzae cells, and to characterize dependence of competence-induced transcription on known regulatory factors. This analysis confirmed the existence of a postulated competence regulon, characterized by a promoter-associated 22 bp competence regulatory element (CRE) closely related to the cAMP receptor protein (CRP) binding consensus. This CRE regulon contains 25 genes in 13 transcription units, only about half of which have been previously associated with competence. The new CRE genes encode a periplasmic ATP-dependent DNA ligase, homologs of SSB, RadC and the Bacillus subtilis DNA uptake protein ComEA, and eight genes of unknown function. Competence-induced transcription of genes in the CRE regulon is strongly dependent on cAMP, consistent with the known role of catabolite regulation in competence. Electrophoretic mobility-shift assays confirmed that CRE sequences are a new class of CRP-binding site. The essential competence gene sxy is induced early in competence development and is required for competence-induced transcription of CRE-regulon genes but not other CRP-regulated genes, suggesting that Sxy may act as an accessory factor directing CRP to CRE sites. Natural selection has united these 25 genes under a common regulatory mechanism. Elucidating this mechanism, and the functions of the genes, will provide a valuable window into the evolutionary function of natural competence.
Assuntos
Proteína Receptora de AMP Cíclico/metabolismo , Regulação Bacteriana da Expressão Gênica/genética , Genes Bacterianos/genética , Haemophilus influenzae/genética , Regulon/genética , Elementos de Resposta/genética , Transformação Bacteriana/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Meios de Cultura/farmacologia , AMP Cíclico/farmacologia , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Ensaio de Desvio de Mobilidade Eletroforética , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Haemophilus influenzae/efeitos dos fármacos , Análise de Sequência com Séries de Oligonucleotídeos , Transativadores/genética , Transativadores/metabolismoRESUMO
The association between sickle cell trait (SCT) and adverse effects of exercise has been controversial. While individuals with SCT are at higher risk of sudden death, the mechanism for this outcome remains to be elucidated. In order to shed light on this controversy, we have monitored venous blood count and blood gas parameter values in normal and SCT subjects during treadmill exercise. White and red blood cell counts and hemoglobin changed significantly over time in both the SCT and normal groups, with peak exercise values different from pre-exercise or post-exercise values. Red blood cell counts showed significant group-time interaction; increase in count during exercise was accentuated in SCT subjects. All blood gas parameters showed significant changes over time in both groups. O2 content was significantly higher in SCT than AA at all time intervals. O2 saturation, pO2 and CO binding to hemoglobin showed significant group-time interaction. Furthermore, O2 saturation for the combined groups was significantly greater at peak exercise and at rest than before exercise. It is possible that treadmill exercise causes microvascular shunting in SCT subjects, leading to a decrease in the peripheral utilization of oxygen.
Assuntos
Contagem de Células Sanguíneas , Dióxido de Carbono/sangue , Exercício Físico/fisiologia , Oxigênio/sangue , Traço Falciforme/sangue , Adulto , Bicarbonatos/sangue , Contagem de Eritrócitos , Hematócrito , Hemoglobinas/metabolismo , Humanos , Contagem de Leucócitos , MasculinoRESUMO
Unlike PMA, bryostatin 1 has been found to have a minimal effect on drug-induced topoisomerase II-mediated DNA cleavage and no effect on topoisomerase II mRNA levels. Furthermore, bryostatin 1 overcame the down-regulatory effects of PMA treatment on (1) drug-induced, topoisomerase II-mediated DNA cleavage, (2) drug-induced cytotoxicity, and (3) topoisomerase II gene expression. Thus, it is unlikely that the effects of phorbol ester treatment on topoisomerase II-mediated events are a direct consequence of protein kinase C activation per se. Rather, the results with bryostatin 1 suggest that the phorbol ester effects are related to more distal effects of phorbol ester treatment that may be related to monocytoid differentiation.
Assuntos
DNA Topoisomerases Tipo II/metabolismo , DNA Topoisomerases Tipo I/metabolismo , DNA/metabolismo , Lactonas/farmacologia , Leucemia/enzimologia , Briostatinas , DNA Topoisomerases Tipo II/genética , Ativação Enzimática/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Humanos , Leucemia/genética , Macrolídeos , Ésteres de Forbol/farmacologia , Proteína Quinase C/metabolismo , RNA Mensageiro/análise , Células Tumorais Cultivadas/efeitos dos fármacosRESUMO
An extensively conjugated phenol (A274), recently shown to be present as a common trace constituent in randomly selected batches of commercial tissue culture media, was diazomethylated; the monomethyl derivative so prepared was shown to exhibit gas chromatographic and mass spectrometric properties identical to those observed for synthetically prepared 9-(4-methoxyphenyl)xanthene, but different from those of several isomeric compounds. The structure 9-(4-hydroxyphenyl)xanthene is thus proposed for A274.