RESUMO
The purpose of this study was to identify performance measures of racially underrepresented minority (RUM) Ph.D. trainees who needed additional training initiatives to assist with completing the UAMS biomedical science degree. A sample of 37 trainees in the 10-year NIH-NIGMS funded Initiative for Maximizing Student Development (IMSD) program at the University of Arkansas for Medical Sciences (UAMS) were examined. Descriptive statistics and correlations examined process measures (GRE scores, GPAs, etc.) and outcome measures (time-to-degree, publications, post-doctoral fellowship, etc.) While differences were found, there were no statistically significant differences between how these two groups (Historically Black Colleges and Universities (HBCUs) and Predominately White Institutions (PWIs)) of students performed over time as Ph.D. students. Graduates who scored lower on the verbal section of the GRE also had a higher final graduate school grade point average in graduates who received their undergraduate training from HBCUs. Of the graduates who received their undergraduate training from PWIs, graduates who scored lower on the quantitative section of the GRE had higher numbers of publications. These findings stimulate the need to 1) reduce reliance on the use of the GRE in admission committee decisions, 2) identify psychometrically valid indicators that tailored to assess outcome variables that are relevant to the careers of biomedical scientists, and 3) ensure the effective use of the tools in making admission decisions.
Assuntos
Sucesso Acadêmico , Educação de Pós-Graduação/estatística & dados numéricos , Grupos Minoritários/estatística & dados numéricos , Critérios de Admissão Escolar/estatística & dados numéricos , Adulto , Arkansas , Pesquisa Biomédica/educação , Educação de Pós-Graduação/métodos , Avaliação Educacional/estatística & dados numéricos , Feminino , Humanos , Masculino , Estudantes/estatística & dados numéricos , Universidades , Adulto JovemRESUMO
Staphylococcus aureus produces a wide array of virulence factors and causes a correspondingly diverse array of infections. Production of these virulence factors is under the control of a complex network of global regulatory elements, one of which is sarA. sarA encodes a DNA binding protein that is considered to function as a transcription factor capable of acting as either a repressor or an activator. Using competitive ELISA assays, we demonstrate that SarA is present at approximately 50 000 copies per cell, which is not characteristic of classical transcription factors. We also demonstrate that SarA is present at all stages of growth in vitro and is capable of binding DNA with high affinity but that its binding affinity and pattern of shifted complexes in electrophoretic mobility shift assays is responsive to the redox state. We also show that SarA binds to the bacteriophage lambda (lambda) attachment site, attL, producing SarA-DNA complexes similar to intasomes, which consist of bacteriophage lambda integrase, Escherichia coli integration host factor and attL DNA. In addition, SarA stimulates intramolecular excision recombination in the absence of lambda excisionase, a DNA binding accessory protein. Taken together, these data suggest that SarA may function as an architectural accessory protein.
Assuntos
Proteínas de Bactérias/metabolismo , Bacteriófago lambda/enzimologia , Proteínas de Ligação a DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Integrases/biossíntese , Staphylococcus aureus/fisiologia , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Sítios de Ligação Microbiológicos , Sequência de Bases , DNA Bacteriano/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Escherichia coli/genética , Escherichia coli/virologia , Humanos , Concentração de Íons de Hidrogênio , Modelos Moleculares , Dados de Sequência Molecular , Oxirredução , Ligação Proteica , Estrutura Terciária de Proteína , Recombinação Genética , Alinhamento de SequênciaRESUMO
The staphylococcal accessory regulator locus (sarA) encodes a DNA-binding protein (SarA) that modulates expression of over 100 genes. Whether this occurs via a direct interaction between SarA and cis elements associated with its target genes is unclear, partly because the definitive characteristics of a SarA binding site have not been identified. In this work, electrophoretic mobility shift assays (EMSAs) were used to identify a SarA binding site(s) upstream of the SarA-regulated gene cna. The results suggest the existence of multiple high-affinity binding sites within the cna promoter region. Using a SELEX (systematic evolution of ligands by exponential enrichment) procedure and purified, recombinant SarA, we also selected DNA targets that contain a high-affinity SarA binding site from a random pool of DNA fragments. These fragments were subsequently cloned and sequenced. Randomly chosen clones were also examined by EMSA. These DNA fragments bound SarA with affinities comparable to those of recognized SarA-regulated genes, including cna, fnbA, and sspA. The composition of SarA-selected DNAs was AT rich, which is consistent with the nucleotide composition of the Staphylococcus aureus genome. Alignment of selected DNAs revealed a 7-bp consensus (ATTTTAT) that was present with no more than one mismatch in 46 of 56 sequenced clones. By using the same criteria, consensus binding sites were also identified upstream of the S. aureus genes spa, fnbA, sspA, agr, hla, and cna. With the exception of cna, which has not been previously examined, this 7-bp motif was within the putative SarA binding site previously associated with each gene.