The Regulatory Function Played By Neuronal Restrictive Silencer Factor On Islet-related Genes

NRSF plays functional role in insulin and CART transcriptionThe transcriptional repressor RE1 silencer transcription factor (NRSF/REST) is an important factor that restricts some neuronal traits in neurons. Since these traits are also present in pancreatic islet cells, we searched NRSF-regulated genes involved in islet function. A NRSE-like motif was analysed in human insulin promoter. We evaluated its role by generating a model of insulin-secreting cells that stabley express NRSF. The presence of NRSF led to a decrease in activity of human insulin promoter by stable or transient transfection with human insulin-promoter luciferase. The predicted NRSE-like motif also confers NRSF-dependent transcriptional repression in the context of a surrogate gene promoter. Specific binding activity of NRSF/REST to the NRSE-like motif was confirmed by EMSA. These data showed that human insulin promoter is regulated by the transcriptional repressor NRSF/REST via the NRSE-Like motif.A NRSE-like motif identified in the upstream CART promoter is confirmed to bind to The factor NRSF in sequence-specific mannerby by EMSA and chromatin immunoprecipitation assays, respectively. Using cotransfection Studies, we showed that the NRSE confers NRSF-dependent trancriptional repression in NRSF-negative cells (PC 12, INS-1) with or without the contex of a surrogate gene promoter. The introduction of mutated NRSE or NRSE-deleted promoter relieved the repression activity in NRSF-positive cells. When the NRSF was disrupted in HeLa cells using small interfering RNA, the transcription of the endogenous target CART gene and NRSE-reporter increased significantly. Taken together, our data suggested that NRSF can function as a repressor of CART transcription, via a mechanism dependent on the CART NRSE.