RESUMO
BACKGROUND: A marked decrease in the level of zinc is a consistent characteristic of prostate cancer; which results from down-regulation of ZIP1 zinc transporter. The aim of this study was to determine if RREB-1 transcription is involved in the down-regulation of ZIP1 gene expression; and to determine the expression of RREB-1 in benign and cancerous prostate in situ. METHODS: Overexpression and siRNA knock down of RREB-1 were used to determine the effect of RREB-1 on hZIP1 abundance in PC-3 cells. Immunohistochemistry with tissue microarrays (TMAs) and tissue sections was used to determine the levels of RREB-1 expression in prostate in situ. RESULTS: Overexpression of RREB-1 resulted in a decrease in the abundance of hZIP1 in the plasma membrane of PC-3 cells; whereas siRNA knock down significantly increased hZIP1 expression. Prostate TMAs and tissue sections showed an inverse relationship between RREB-1 and hZIP1 staining. CONCLUSIONS: RREB-1 overexpression results in down-regulation of hZIP1 and contributes to the loss of hZIP1 expression and zinc in prostate cancer. This is an early event in prostate carcinogenesis.
Assuntos
Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Proteínas de Ligação a DNA/genética , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismo , Fatores de Transcrição/genética , Adenocarcinoma/patologia , Adulto , Idoso , Biópsia , Proteínas de Transporte de Cátions/genética , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/metabolismo , Regulação para Baixo/fisiologia , Epigênese Genética/fisiologia , Regulação Neoplásica da Expressão Gênica , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias da Próstata/patologia , RNA Interferente Pequeno/genética , Fatores de Transcrição/metabolismo , Zinco/metabolismoRESUMO
BACKGROUND: Normal prostate accumulates extremely high levels of zinc compared to other soft tissues. In contrast, the level of zinc in the prostate decreases significantly in prostate cancer. We have shown that down-regulation of the expression of the zinc transporter hZIP1 in prostate cancer is an important event that is responsible for the decrease of zinc levels. However, the mechanism of hZIP1 down-regulation is not known. We have hypothesized that hZIP1 is down-regulated through transcriptional regulation. METHODS: The hZIP1 promoter was studied using luciferase reporter assays, site-directed mutagenesis, gel shift, and ChIP assay. RESULTS: We have characterized a promoter region, downstream of the transcription start site, responsible for repression of hZIP1 transcription. We demonstrate that this region contains a binding site for the Ras-Responsive Element Binding protein 1 (RREB-1) and that the binding of RREB-1 to the hZIP1 promoter is involved in the decrease of hZIP1 transcription in PC-3 cells. CONCLUSION: The Ras pathway and activation of RREB-1 are involved in hZIP1 down-regulation and may play a role in the decrease of the transporter expression in prostate cancer.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , Proteínas de Ligação a DNA/metabolismo , Neoplasias da Próstata/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Bases , Sítios de Ligação/genética , Proteínas de Transporte de Cátions/genética , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/genética , Regulação para Baixo , Humanos , Luciferases/metabolismo , Masculino , Dados de Sequência Molecular , Regiões Promotoras Genéticas , RNA Interferente Pequeno/farmacologia , Fatores de Transcrição/genética , Sítio de Iniciação de Transcrição , Transcrição Gênica , Proteínas ras/metabolismoRESUMO
Theoretical models suggest that gene silencing at the nuclear periphery may involve "closing" of chromatin by transcriptional repressors, such as histone deacetylases (HDACs). Here we provide experimental evidence confirming these predictions. Histone acetylation, chromatin compactness, and gene repression in lamina-interacting multigenic chromatin domains were analyzed in Drosophila S2 cells in which B-type lamin, diverse HDACs, and lamina-associated proteins were downregulated by dsRNA. Lamin depletion resulted in decreased compactness of the repressed multigenic domain associated with its detachment from the lamina and enhanced histone acetylation. Our data reveal the major role for HDAC1 in mediating deacetylation, chromatin compaction, and gene silencing in the multigenic domain, and an auxiliary role for HDAC3 that is required for retention of the domain at the lamina. These findings demonstrate the manifold and central involvement of class I HDACs in regulation of lamina-associated genes, illuminating a mechanism by which these enzymes can orchestrate normal and pathological development.