Received for publication February 17, 2006.
Revised April 28, 2006.
Accepted for publication April 28, 2006.

Hepatocyte nuclear factors 1 and 4 (HNF1 & HNF4) mediates hepatic MRP2 up-regulation during hepatitis C virus gene expression

Abstract

Hepatitis C virus (HCV) is known to induce hepatic oxidative stress which is implicated in the up regulation of multidrug resistance proteins (MRPs). The relationship between increased prooxidant production, MRPs and HCV has not been investigated. Here, we report that a homeodomain containing transcription factor, hepatocyte nuclear factor-1 (HNF-1) plays a central role in liver gene regulation during HCV gene expression and/or subgenome replication. MRP2 protein and mRNA expression was increased and MRP2 promoter activity was increased 7-fold. Mutations within the putative HNF1 binding site of the human MRP2 promoter abrogated HCV-induced activation, thus implicating HNF1 in the induction of MRP2 by HCV. The mechanism by which HNF1-mediated activation occurs appears to be transcriptional, as the regulated expression of HNF4, that is known to control HNF1 expression, was also increased. Consistent with this, HNF1 mRNA was increased 10 fold. A promoter-luciferase construct of the human HNF1 gene was activated in an HNF4-dependent manner, and a mutant construct lacking the HNF4 binding site was not activated in HCV-positive cells. Consistent with this hypothesis, HNF4 protein and mRNA levels, as well as HNF4 promoter activity and DNA binding activity were increased. The expression of HNF1 seems to play a critical role in the induction of hepatic MRP2 secondary to HCV subgenomic replication. The ability of HCV to induce HNF1 and HNF4 is attributed to 1) increased oxidative stress and 2) direct protein-protein interactions between HCV NS5A and HNF1, leading to enhanced HNF1 DNA binding. In conclusion, we describe novel mechanism, by which HCV gene expression may induce adaptive responses, involving MRP2 via HNF1 activation. This in part may constitute the cellular detoxification task force during HCV infection.

Key words: DNA binding sites, Promoter analysis, Organic anion, Liver transporters, Structure/function/mechanism, Oxidative stress/antioxidants