Molecular Mechanisms Regulating Transcription of the Renin Gene.

For the past 10 years we have been examining the regulation of the gene encoding a protein (renin) central to the regulation of blood pressure and water and electrolyte homeostasis.  We have identified a strong enhancer of transcription 2.6 kb upstream of the mouse renin gene and its homolog 13.0 kb upstream of the human renin gene.  This enhancer is a complex regulatory element consisting of the binding sites for at least 7 different transcription factors including NF-Y, RARa, RXRa, CREM, CREB, USF-1 and USF-2.  These transcription factors serve to both up-regulate and down-regulate renin expression in response to physiological cues.  Using yeast one-hybrid analysis, we recently determined that Ear2, an orphan member of the nuclear hormone super-family, is a strong negative regulator of renin expression.  It represses transcription by binding to the same site as RARa on the enhancer and may therefore compete with it for binding.  We have also generated a number of transgenic mouse models to examine the regulation of renin transcription.  The most important model consists of a 160 kb P1 artificial chromosome (called PAC160) construct which contains the renin gene as well as the upstream PEPP3 and Kiss1 genes and the downstream FLJ10761 and Sox13 genes.  The regulation of renin transcription from this construct is exquisitely tight, responding exactly as anticipated to physiological signals which normally regulate the renin gene.  We are currently performing mutagenesis of each of the transcription factor binding sites in this PAC construct to assess their importance in tissue- and cell-specific expression of renin, its response to hormonal stimulation and its response to physiological signals.  We are also determining if the enhancer influences the transcription of the nearby upstream and downstream genes.