RESUMO
To identify a new morphological phenotype of erythromycin (EM)-resistant Staphylococcus aureus (S. aureus) were isolated in vitro from EM-sensitive parent strain, and the distribution of staphylococcus specific protein A (SpA) on the surface of these strains was examined morphologically by using applied immunoelectron microscopy. The isolated EM-resistant strains had thickened cell walls, and the distribution of SpA on the surfaces of these strains was demonstrated to be lower than that of the parent strain. The SpA suppression was confirmed by enzyme-linked immunosorbent assay (ELISA) using fixed EM-resistant cells. Moreover, the spa gene of EM-resistant cells was detected by polymerase chain reaction (PCR) and confirmed by quantitative real-time PCR assay, showing that the expression of SpA was repressed at the transcriptional level in these strains. Furthermore, ELISA assay showed that whole EM-resistant cell SpA content was significantly decreased. Therefore, it was considered that the suppression of surface SpA on the EM-resistant strain was due to regulated SpA production, and not dependent on the conformational change in SpA molecule expression through cell wall thickening. These results strongly suggest that suppressed SpA distribution on the EM-resistant S. aureus is a phenotypical characteristic in these strains.
Assuntos
Farmacorresistência Bacteriana , Eritromicina , Proteína Estafilocócica A , Staphylococcus aureus , Eritromicina/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/genética , Staphylococcus aureus/metabolismo , Proteína Estafilocócica A/genética , Proteína Estafilocócica A/metabolismo , Farmacorresistência Bacteriana/genética , Antibacterianos/farmacologia , Parede Celular/metabolismo , Parede Celular/efeitos dos fármacos , Parede Celular/ultraestrutura , Ensaio de Imunoadsorção Enzimática , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacosRESUMO
Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded latency-associated nuclear antigen (LANA), which interacts with cellular proteins, plays a central role in modification of viral and/or cellular gene expression. Here, we show that LANA associates with glucocorticoid receptor (GR), and that LANA enhances the transcriptional activity of GR. Co-immunoprecipitation revealed a physical interaction between LANA and GR in transiently transfected 293T and HeLa cells. In human B-lymphoma cells, LANA overexpression enhanced GR activity and cell growth suppression following glucocorticoid stimulation. Furthermore, confocal microscopy showed that activated GR was bound to LANA and accumulated in the nucleus, leading to an increase in binding of activated GR to the glucocorticoid response element of target genes. Taken together, KSHV-derived LANA acts as a transcriptional co-activator of GR. Our results might suggest a careful use of glucocorticoids in the treatment of patients with KSHV-related malignancies such as Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease.
Assuntos
Antígenos Virais/metabolismo , Herpesvirus Humano 8/fisiologia , Interações Hospedeiro-Patógeno , Proteínas Nucleares/metabolismo , Receptores de Glucocorticoides/metabolismo , Sarcoma de Kaposi/metabolismo , Sarcoma de Kaposi/virologia , Linfócitos B/metabolismo , Linfócitos B/virologia , Linhagem Celular , Linhagem Celular Tumoral , Proliferação de Células , DNA/metabolismo , Células HeLa , Humanos , Receptores de Glucocorticoides/genética , Sarcoma de Kaposi/genética , Ativação TranscricionalRESUMO
The Epstein-Barr virus (EBV)-encoded latency protein EBNA2 is a nuclear transcriptional activator that is essential for EBV-induced cellular transformation. Here, we show that EBNA2 interacts with STAT3, a signal transducer for an interleukin-6 family cytokine, and enhances the transcriptional activity of STAT3 by influencing its DNA-binding activity. Furthermore, EBNA2 cooperatively acts on STAT3 activation with LMP1. These data demonstrate that EBNA2 acts as a transcriptional coactivator of STAT3.
Assuntos
Antígenos Nucleares do Vírus Epstein-Barr/metabolismo , Herpesvirus Humano 4/metabolismo , Fator de Transcrição STAT3/metabolismo , Ativação Transcricional , Proteínas Virais/metabolismo , Células HeLa , Herpesvirus Humano 4/genética , Humanos , Fator de Transcrição STAT3/genética , Proteínas da Matriz Viral/metabolismoRESUMO
The Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded latency-associated nuclear antigen (LANA) is known to modulate viral and cellular gene expression. We show that LANA directly associates with an interleukin-6 signal transducer, signal transducer and activator of transcription 3 (STAT3) and that LANA enhances the transcriptional activity of STAT3. Coimmunoprecipitation studies documented a physical interaction between LANA and STAT3 in transiently transfected 293T cells as well as the KSHV-infected primary effusion lymphoma (PEL) cell line. Furthermore, small-interfering RNA-mediated reduction of LANA expression decreased the STAT3-dependent transcription in KSHV-positive PEL cells, whereas overexpression of LANA enhanced STAT3 activity in KSHV-negative B lymphoma cells. These data demonstrate that LANA is a transcriptional co-activator of STAT3, and may have implications for the pathogenesis of KSHV-associated diseases.
