RESUMEN

The regulatory elements that control basal and activated transcriptional expression of the polymeric IgA receptor gene (pIgR) have not been defined. In this study, we performed functional analysis of the murine pIgR 5'-upstream region. Transient transfection studies identified the gene's minimal promoter to reside within 110 nucleotides upstream from the start of transcription. Substitution mutations of this region identified both a putative activator (-78 to -70) and a repressor (-66 to -52) element. DNase I footprint analysis confirmed an area of protection that spans from nucleotides -85 to -62. Mobility shift assays of the putative region confirmed binding of upstream stimulatory factor 1 (USF1) to an E box element at positions -75 and -70, representing the putative enhancer. Overexpression studies using various forms of USF suggest that both USF1 and USF2 enhance activity of the pIgR minimal promoter. We report the identification and characterization of the murine pIgR minimal promoter, as well as the critical role of USF in enhancing its basal level of transcription in Caco-2 cells.

Asunto(s)

Intestino Delgado/metabolismo , Receptores Fc/genética , Secuencias Reguladoras de Ácidos Nucleicos , Transcripción Genética , Envejecimiento , Animales , Secuencia de Bases , Sitios de Unión , Línea Celular , Proteínas de Unión al ADN/metabolismo , Elementos de Facilitación Genéticos , Exones , Biblioteca Genómica , Humanos , Inmunoglobulina A/metabolismo , Intestino Delgado/crecimiento & desarrollo , Ratones/genética , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Oligodesoxirribonucleótidos , Reacción en Cadena de la Polimerasa , Regiones Promotoras Genéticas , Ratas/genética , Receptores Fc/biosíntesis , Proteínas Recombinantes/biosíntesis , Alineación de Secuencia , Homología de Secuencia de Aminoácido , TATA Box , Transfección