Exonic Sp1 sites are required for neural-specific expression of the glycine receptor β subunit gene

Abstract

The gene encoding the beta subunit of the inhibitory glycine receptor (GlyR) is widely expressed throughout the mammalian central nervous system. To unravel the elements regulating its transcription, we isolated its 5' non-coding and upstream flanking regions from mouse. Sequence analysis revealed significant differences between the 5' region of the beta subunit gene and the corresponding regions of the homologous GlyR alpha subunit genes; it also identified a novel exon (exon 0) that encodes most of the 5'-untranslated portion of the GlyR beta mRNA. Primer extension experiments disclosed multiple transcriptional start sites. Transfection experiments with luciferase reporter gene constructs showed that sequences encompassing 1.58 kb of upstream flanking region and 180 bp of exon 0 displayed high promoter activity in two neuroblastoma cell lines but not in non-neural cells. Analysis of various deletion constructs showed that the 5' flanking region preceding the transcriptional start sites silences expression in non-neural cells but is not essential for general promoter activity. In contrast, the deletion of sequences within exon 0 drastically decreased or abolished transcription; the removal of sequences harbouring Sp1 consensus sequences within exon 0 decreased expression specifically in a neuroblastoma cell line. Band-shift assays confirmed the binding of Sp1 to sites within the deleted sequence. Our results indicate that neural-specific expression of the GlyR beta subunit gene might depend on a direct interaction of Sp1 transcription factors with cis elements located downstream from transcription initiation sites.

Regulation of transcription of the human MRP7 gene

“…A recent article published in FASEB (Ge et al, 2004) showed that one tsp within the human BACE gene promoter was 224 nt upstream and a second tsp was 376 nt further upstream of the basal promoter. An earlier report by Tintrup et al (2001) made similar observations and suggested on the basis of this and other reports cited that tsps remotely situated relative to the basal promoter are characteristic of promoters with multiple Sp1 sites embedded in this region.…”

Mithramycin A suppresses expression of the human melanoma-associated gene ABCB8

“…Sp1 and Sp3 are thought to be ubiquitously expressed, but these factors have also been implicated in cell typespeciWc regulation of several genes (Heicklen-Klein and Ginzburg 2000; Tintrup et al 2001;Valin et al 2009). Furthermore, the level of Sp1 expression may be highly variable between tissues, as has been shown in developmental studies in mice (SaVer et al 1991).…”

Sp1 and Sp3 regulate transcription of the cyclin-dependent kinase 5 regulatory subunit 2 (p39) promoter in neuronal cells

“…The p39 promoter lacks sequences resembling common core promoter elements such as initiator, DPE or BRE, which are present in many TATA-less promoters (for example the p35 promoter [11]) [21] REF. Multiple transcription start sites are a common feature of TATA-less promoters, and are found frequently in promoters of cell-type specific genes [22–24]. …”

“…Although Sp1 and Sp3 are ubiquitously expressed, these transcription factors have been implicated in cell type-specific regulation of several genes in neurons [24, 31, 32]. We have previously reported that a repeated GC box that binds Sp1, Sp3 and Sp4 in vitro is necessary and sufficient for neuron-specific expression of the cdk5 regulator p35 [11].…”