Differential regulation by multiple promoters of the gene encoding the neuron-restrictive silencer factor

NRSF/REST is a protein that silences transcription of a number of genes tha t contain a DNA element called the neuron-restrictive silencer element (NRS E). During embryogenesis, REST is expressed ubiquitously in nonneural cells , but is down-regulated during differentiation of neural progenitors into n eurons. REST is also up-regulated in adult neurons by activity, suggesting a possible role for the protein in synaptic plasticity. To understand mecha nisms that control expression of REST, we identified and characterized the promoter region of the mouse REST gene (mREST). A 4.5-kb DNA segment contai ning three exons (A, B, and C) that correspond to alternatively spliced 5' untranslated regions (5'UTRs) was isolated and its DNA sequence was determi ned. Reverse transcription-PCR analyses of fibroblasts, astrocytes, and neu ral progenitors identified variants in which these exons were spliced to ex on D, suggesting that exons A, B, and C may each have a promoter. Consisten t with this hypothesis, primer extension and in vitro transcription experim ents revealed clusters of RNA transcription initiation sites upstream of ex ons A, B, and C. Tests of REST/luciferase reporter constructs in Neuro2A an d NIH 3T3 cells revealed promoters upstream of exons A and B that were acti ve in both cell lines, and a promoter upstream of exon C that was weakly ac tive only in NIH 3T3 cells. Six enhancer and two repressor regions were fou nd to overlap each of the three promoters, and some of these were found to be cell type-specific. Combinatorial arrangements of these promoters with e nhancer and repressor regions may allow modulation of REST expression in pa rticular contexts.