SEQUENCE-ANALYSIS AND FUNCTIONAL-CHARACTERIZATION OF THE 5'-FLANKING REGION OF THE RAT MULTIDRUG-RESISTANCE PROTEIN-2 (MRP2) GENE

Gene expression of the canalicular conjugate transporter mrp2 is induc ible by treatment with the DNA-damaging agents 2-acetylaminofluorene ( 50 and 100 mu M), and cisplatin (20 mu M) in primary rat hepatocytes a s well as in the rat hepatoma cell line H4IIE. Furthermore, phenobarbi tal (1 and 2 mM) induces mrp2 gene expression, probably explaining the increase in bile-salt-independent bile now caused by phenobarbital, w hile the cholestatic drug ethinyl estradiol (10(-6) M) leads to an inc rease in mrp2 mRNA but decreases Mrp2 protein level probably via a pos ttranscriptional mechanism. The 5'-flanking region of the rat mrp2 gen e was sequenced and cloned into a luciferase reporter vector. Transien t transfection assays with reporter vectors containing unidirectionall y deleted 5'-flanking regions using H4IIE cells indicate that two diff erent sequences of 17 and 37 bases comprising a Y-Box and a GC-Box are required for mrp2 gene basal expression. Sequences mediating 2-AAF in duction are located within a region 250 bases upstream of the translat ion start site while the inducing effect of phenobarbital seems to be mediated by another domain located further upstream. (C) 1998 Academic Press.