RESUMO
Understanding transcription initiation of the endothelial nitric-oxide synthase (eNOS) gene appears pivotal to gaining a comprehensive view of NO biology in the blood vessel wall. The present study therefore focused upon a detailed dissection of the functionally important cis-DNA elements and the multiprotein complexes implicated in the cooperative control of constitutive expression of the human eNOS gene in vascular endothelium. Two tightly clustered cis-regulatory regions were identified in the proximal enhancer of the TATA-less eNOS promoter using deletion analysis and linker-scanning mutagenesis: positive regulatory domains I (-104/-95 relative to transcription initiation) and II (-144/-115). Analysis of trans-factor binding and functional expression studies revealed a surprising degree of cooperativity and complexity. The nucleoprotein complexes that form upon these regions in endothelial cells contained Ets family members, Sp1, variants of Sp3, MAZ, and YY1. Functional domain studies in Drosophila Schneider cells and endothelial cells revealed examples of positive and negative protein-protein cooperativity involving Sp1, variants of Sp3, Ets-1, Elf-1, and MAZ. Therefore, multiprotein complexes are formed on the activator recognition sites within this 50-base pair region of the human eNOS promoter in vascular endothelium.
Assuntos
Óxido Nítrico Sintase/genética , Regiões Promotoras Genéticas , Animais , Sequência de Bases , Domínio Catalítico/genética , DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Drosophila , Proteínas de Drosophila , Endotélio Vascular/enzimologia , Regulação Enzimológica da Expressão Gênica , Humanos , Dados de Sequência Molecular , Mutagênese Insercional , Óxido Nítrico Sintase Tipo III , Deleção de Sequência , Fator de Transcrição Sp1/metabolismo , Relação Estrutura-Atividade , Fatores de Transcrição/metabolismoRESUMO
As our understanding of the contributory roles of NO in the blood vessel wall evolves, so does the need to firmly understand the basic principles governing the regulated expression of the endothelial nitric oxide synthase (eNOS) gene. Because a robust approach to dissecting the relative contribution of a given cardiovascular gene exploits the use of murine genetic models, P1 murine genomic clones were isolated, characterized and functionally assessed to gain further insight into the regulated expression of the eNOS gene in the mouse. Sequence analysis of 1.8 kb of 5' flanking regions revealed important regions of sequence conservation with human and bovine sequences. Functional promoter activity was confirmed using transient transfection analysis of cultured endothelial cells.
