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Summary. Background: Hepatitis C virus (HCV) translation is initiated in a cap-independent manner by an internal ribosome entry site (IRES) located within the 5′ untranslated region (5′UTR). Sequence changes in this region could affect translation efficiency and presumably viral replication. Aim: To determine translation efficiency of 5′UTR variants developing during post-transfusion hepatitis C in two immunocompetent subjects and in two immunosuppressed liver recipients with recurrent HCV. Methods: Sequential samples were screened for 5′UTR changes by single-strand conformation polymorphism followed by cloning and sequencing whenever band pattern suggested sequence changes. 5′UTR variants were tested for IRES activity using a bicistronic dual luciferase expression plasmid transfected into HepG2 and Huh7 cell-lines. Results: In the transfused patients, translation efficiency of 5′UTR variants from early post-transfusion samples was 5.1- to 13.7-fold higher than that of predominant variants found in late follow-up samples. Post-transplant variants in the other two patients had 2.6- to 5.9-fold higher translation efficiency than those present only in pretransplant samples. Conclusion: In the immunocompetent host there may be selection of low translation efficiency HCV variants over the course of infection. However, in immunosuppressed subjects the opposite seems to be true as low translation efficiency variants are superseded by high translation efficiency variants.

Hepatitis C virus (HCV) is the major etiological agent of blood-borne non-A non-B hepatitis and a leading cause of liver cirrhosis and hepatocellular carcinoma worldwide. HCV core protein is a multifunctional protein with regulatory functions in cellular transcription and virus-induced transformation and pathogenesis. Here we report on the identification of a bZIP nuclear transcription protein as an HCV core cofactor for transformation. This bZIP factor, designated LZIP, activates CRE-dependent transcription and regulates cell proliferation. Loss of LZIP function in NIH 3T3 cells triggers morphological transformation and anchorage-independent growth. We show that HCV core protein aberrantly sequesters LZIP in the cytoplasm, inactivates LZIP function and potentiates cellular transformation. Our findings suggest that LZIP might serve a novel cellular tumor suppressor function that is targeted by the HCV core., published_or_final_version