Hepatitis C virus core protein and cellular protein HAX-1 promote 5-fluorouracil-mediated hepatocyte growth inhibition.
Hepatitis C virus (HCV) often causes chronic infection and may lead to hepatocellular carcinoma (HCC). We have shown previously that HCV core protein has pleiotropic functions, including transcriptional regulation of a number of cellular genes, although the mechanism for gene regulation remains unclear. In this study, a mammalian two-hybrid screen identified a novel binding partner, HS1-associated protein X-1 (HAX-1), for HCV core protein from a human liver cDNA library. An association between HAX-1 and HCV core protein was further verified by confocal microscopy and coimmunoprecipitation in HepG2 cells expressing HCV core or full-length (FL) gene. Both HCV core protein and a chemotherapeutic agent for HCC, 5-flouorouracil (5-FU), are known to modulate p53. We examined here whether an association between core and HAX-1 has any functional relevance to p53 modulation in 5-FU-treated cells. For this, the role of HAX-1 on 5-FU treatment was examined in HepG2 cells expressing HCV core or FL gene using cell proliferation, p53 expression, and caspase activation analysis. Cells expressing HCV-core or FL gene were more susceptible to 5-FU-induced growth inhibition than control cells, whereas cell survival was enhanced after suppression of HAX-1 by small interfering RNA. Further, 5-FU-mediated p53 expression was reduced with concurrent HAX-1 suppression in core- or polyprotein-expressing cells compared to control HepG2 cells, and caspase-2 and -7 activities were diminished. On the other hand, HCV core protein did not play a detectable role in 5-FU-mediated caspase-7 activation in the absence of functional p53 in Hep3B or Huh-7 cells. These observations underscore an association between HCV core and HAX-1, which promotes 5-FU mediated p53-dependent caspase-7 activation and hepatocyte growth inhibition.
Banerjee
Arup
A
Department of Internal Medicine, Saint Louis University, St. Louis, Missouri 63119, USA.
Saito
Kousuke
K
Meyer
Keith
K
Banerjee
Sutapa
S
Ait-Goughoulte
Malika
M
Ray
Ratna B
RB
Ray
Ranjit
R
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D019556:COS Cells; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D005472:Fluorouracil / Q000494:pharmacology*; D022781:Hepatocytes / Q000821:virology*; D006801:Humans; D018613:Microscopy, Confocal / Q000379:methods; D011506:Proteins / Q000378:metabolism*; D014758:Viral Core Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000964:Antimetabolites, Antineoplastic; D018076:DNA, Complementary; C104759:HAX1 protein, human; D011506:Proteins; D014758:Viral Core Proteins; C069130:nucleocapsid protein, Hepatitis C virus; D053179:Caspase 7; D005472:Fluorouracil