Cell-specific activity of cis-acting regulatory elements in the promoter of the mouse multidrug resistance gene mdr1.

To define cis-acting elements implicated in transcriptional regulation of the mouse multidrug resistance gene mdr1, we have cloned and characterized the 5' end of the gene. Nucleotide sequence analysis identified TATA, GGGCGG, and CCAAT consensus sequence elements at positions -27, -47, and -83, respectively. The transcriptional activities of 5' deletion fragments from the promoter linked to a reporter gene were tested in mouse cell lines of different tissue origins shown to express different levels of endogenous mdr1 RNA. Sequences located between nucleotides -93 and +84 were able to confer basal promoter activity and cell specificity to the reporter gene. The addition to the basal promoter of sequences upstream of position -141 was found to up or down regulate the basal level of expression of the reporter gene in a cell-specific manner.