Regulation of hepatitis C virus translation initiation by iron: Role of eIF3 and La protein

Abstract

Eukaryotic initiation factors (eIFs) are required for encoding polyprotein of hepatitis C virus (HCV) which is mediated by an internal ribosome-entry site (IRES). Iron overload, a common finding among HCV patients, may be correlated with HCV pathology, but the underlying molecular mechanisms are poorly understood. In this study, we investigated the possible relationship among iron status, eIFs and HCV IRES-mediated translation in vitro. Using bicistronic reporter gene constructs carrying HCV IRES sequence, we found that the levels of intracellular iron were positively associated with the HCV IRES-dependent translation initiation in Huh-7 cells. RT-PCR method showed that iron treatment specifically increased the levels of eIF3A mRNA and La mRNA, whereas iron chelation reduced them. Western blots also confirmed that iron-dependent changes in eIF3A mRNA and La mRNA affected the expression of their proteins. Moreover, antisense phosphorothioate oligodeoxynucleotides to eIF3A and La successfully suppressed the levels of eIF3A and La protein and significantly reduced iron-dependent HCV translation. Taken together, our results suggest that iron promotes the translation initiation of HCV by stimulating the expression of eIF3A and La proteins. Inhibition of eIF3A and La proteins substantially repressed iron-dependent HCV translation, a beneficial effect that may have significant clinical implications.