The role of repressor element 1 silencing transcription factor (REST) in modulating the transcription of human secretin receptor gene

Abstract

Recently, we have characterized the human secretin receptor (hSR) gene and demonstrated that the hSR promoter (-263 to -158, relative to the ATG start codon) is controlled by the ratio of activator Sp1 to repressor Sp3 competitively interacting with two GC-boxes. In the present study, a repressor-like element was identified at the 3V region (-101 to -46) of the minimal promoter. Scanning mutations within this region revealed a putative repressor element 1 (RE-1) binding motif. RE-1, also known as neuron-restrictive silencer element, is a 21-bp long, negative-acting DNA regulatory element. RE-1 interacts with a transcription factor, namely RE-1 silencing transcription factor (REST). REST represses gene expression by two repressor domains which recruit mSin3 and CoREST. RE-1 has been identified in an increasing number of neuronal genes, such as type II sodium channel, mu opioid receptor, and GABAA receptor g2. Recently, functional REST sites have also been discovered in VIP and PACAP genes. These observations are consistent with the scanning mutation analysis indicating a relation between RE-1 and hSR gene expression. Competitive gel mobility shift and supershift studies revealed the binding of REST with the RE-1 motif. Over-expression of REST in a REST non-expressing cells, PC12, dramatically decreased the RE-1 containing hSR promoter activity. Consistent with these results, the promoter activity and the transcript level of hSR are also augmented in Panc-1 cells after siRNA knock-down of REST. In summary, hSR gene expression is negatively regulated by REST through the RE-1 motif.