Constitutive rat multidrug-resistance protein 2 gene transcription is down-regulated by Y-box protein 1.
OBJECTIVE
Molecular mechanisms underlying transcriptional rat multidrug-resistance protein 2 (Mrp2, Abcc2) gene regulation are mostly unclear. Given the presence of putative binding sites for the Y-box binding protein YB-1 in the regulatory sequence, its trans-regulatory influence was analyzed.


METHODS
Reporter assays in HepG2 cells with various Mrp2 deletion constructs in the absence and presence of co-transfected YB-1 were performed. DNA binding studies with recombinant YB-1 protein and nuclear extracts obtained from HepG2 cells and rat liver tissue were carried out.


RESULTS
The minimal promoter sequence was confined to the proximal 186 bp. A YB-1 responsive element, Mrp2 YRE-1, was mapped at -186/-157, which exhibits specific YB-1 binding. YB-1 acts as a potent repressor of Mrp2 promoter activity in vitro.


CONCLUSIONS
Constitutive Mrp2 gene expression is conferred through the proximal -186 bp. YB-1 acts as a repressor in vitro by specific binding to a defined element in the proximal promoter sequence.
Geier
A
A
Department of Internal Medicine III, University Hospital, Aachen, Germany.
Mertens
P R
PR
Gerloff
T
T
Dietrich
C G
CG
En-Nia
A
A
Kullak-Ublick
G A
GA
Karpen
S J
SJ
Matern
S
S
Gartung
C
C
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D008297:Male; D008969:Molecular Sequence Data; D051839:NFI Transcription Factors; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism*; D020218:Response Elements; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D051840:Y-Box-Binding Protein 1
D018528:ATP-Binding Cassette Transporters; C423013:Abcc2 protein, rat; D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C486169:Ybx1 protein, rat