RESUMEN
Neuronal cell-specific BC1 RNA is a unique RNA polymerase III (Pol III) transcript. The transcription is controlled by an activator E2 site and by BCRE, a repressor element, in response to neuronal activity. BC1 RNA is localized to dendritic domains as ribonucleoprotein particles, and it has been suggested to play a functional role in translational regulation of dendritic mRNAs. In the present study, using a luciferase assay in NG108-15 cells, we found that the positive and negative regulators for BC1 RNA transcription can also function in the Pol II transcription system. Our results suggest that the neuronal activity-dependent expression of BC1 RNA by Pol III and a subset of neuronal mRNAs by Pol II may be simultaneously controlled by the E2 site and BCRE, as well as their binding proteins.
Asunto(s)
Encéfalo/metabolismo , Genes Reguladores/genética , Neuronas/metabolismo , ARN Polimerasa III/metabolismo , ARN Polimerasa II/metabolismo , ARN Citoplasmático Pequeño/biosíntesis , Transcripción Genética/genética , Animales , Sitios de Unión/genética , Línea Celular , Dendritas/metabolismo , Ratones , Unión Proteica/genética , Biosíntesis de Proteínas/genética , ARN Polimerasa II/genética , ARN Polimerasa III/genética , ARN Mensajero/metabolismo , ARN Citoplasmático Pequeño/genética , Ratas , Proteínas Represoras/genética , Activación Transcripcional/genéticaRESUMEN
The c-erbB-2 oncogene is frequently overexpressed in human breast cancer partly due to its elevated transcription level. The promoter regions of the c-erbB-2 gene could therefore activate the transcription of a linked foreign gene preferentially in breast cancer cells. Previous reports showed that the 533-bp (-495/+38, +1 corresponds to the transcription start site) or the 251-bp (-213/+38) genomic fragment included the cis-acting elements which stimulated the transcription of a fused gene in breast cancer cells. Our previous study also indicated that the 251-bp fragment could transcribe the reporter gene better than the 533-bp fragment and that the 124-bp (-86/+38) region did not support the transcription of a linked reporter gene. In this study, we precisely analyzed the promoter activity of the genomic region between -213/+38 and -86/+38 in breast cancer, non-breast cancer cells and fibroblasts, and found that deletion of 22-bp from the 251-bp fragment markedly decreased the transcriptional activation in breast cancer cells. Although the 22-bp deletion also decreased the promoter activity in non-breast cancer cells, the deletion did not influence the activity in fibroblasts. Since the promoter activity of shorter genomic fragments beyond the 22-bp deletion remained low in breast cancer cells, the -213/-191 region contains a cis-acting element(s) that is minimally required for the preferential expression in breast cancer cells.
