Basal expression of the rat, but not of the human, multidrug resistance protein 2 (MRP2) gene is mediated by CBF/NF-Y and Sp1 promoter-binding sites.
The most important biliary efflux transporter known so far is the multidrug resistance protein 2 (MRP2). Previously, we isolated and characterized the 5'-flanking region of the rat mrp2 gene. In the present study, we performed site-directed mutagenesis experiments indicating that both a Y-Box and a GC-Box in the rat mrp2 promoter are essential for the full basal expression of the gene, but have no significant relevance for its inducibility by the chemical carcinogen 2-acetylaminofluorene. Gel mobility shift experiments demonstrated the binding of the transcription factor CBF/NF-Y, but not of EFIA/YB-1, to the Y-Box. Site-directed mutations in the Y-Box decreasing reporter gene activity of a promoter construct prevented the binding of NF-Y. Consequently, NF-Y contributes substantially to the basal expression of the gene. A site-directed mutation in the GC-Box also reduced basal expression and resulted in a reduced complex formation with the transcription factor Sp1. The corresponding region of the human MRP2 promoter comprises no Sp1 site, but a Y-Box-like element binding YB-1 but not NF-Y, which, however, does not contribute to basal expression. In conclusion, NF-Y and Sp1 binding sites play a decisive role in the basal expression of the rat mrp2 gene, while the human MRP2 gene is regulated differently.
Kauffmann
H M
HM
Food Chemistry and Environmental Toxicology, University of Kaiserslautern, Erwin-Schroedinger-Strasse 52, D-67663 Kaiserslautern, Germany.
Vorderstemann
B
B
Schrenk
D
D
D015073:2-Acetylaminofluorene / Q000494:pharmacology; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters; D000818:Animals; D001665:Binding Sites; D023081:CCAAT-Binding Factor / Q000378:metabolism*; D002273:Carcinogens / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D011401:Promoter Regions, Genetic; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D015073:2-Acetylaminofluorene; D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D023081:CCAAT-Binding Factor; D002273:Carcinogens; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D016329:Sp1 Transcription Factor; C000715087:ABCC2 protein, human; C423013:Abcc2 protein, rat; C421109:multidrug resistance-associated protein 1