The isolation and characterization of the promoter of the human type 1 inositol 1,4,5-trisphosphate receptor

Abstract In humans, at least three types of inositol (1,4,5)-trisphosphate receptor (IP 3 R) are present. The gene encoding type 1 IP 3 R ( IP 3 R-I ) is expressed in all cell types, although expression predominates in Purkinje cells. To study the regulation of the human IP 3 R-I gene, we isolated and characterized a 2.1-kb 5′ flanking region. In transient expression assays using a rat cell line, analysis of various deletion mutants demonstrated that a fragment of only 86 bp 5′ of the putative tsp displayed a promoter activity similar to that of the 2.1-kb fragment. Also, we compared the sequence of the human IP 3 R-I promoter with the sequence of the mouse IP 3 R-I promoter. Considerable sequence homology is present in four distinct domains, which include several conserved putative binding sites for transcription factors. Further, we demonstrate a decrease in the activity of the isolated human IP 3 R-I promoter and of the endogenous IP 3 R-I promoter after 48 h of treatment with retinoic acid. Analysis of deletion constructs of the human promoter indicates that the decreased promoter activity in response to retinoic acid is likely to be mediated by a conserved AP-2 binding site.