POLIOVIRUS CHIMERAS REPLICATING UNDER THE TRANSLATIONAL CONTROL OF GENETIC ELEMENTS OF HEPATITIS-C VIRUS REVEAL UNUSUAL PROPERTIES OF THE INTERNAL RIBOSOMAL ENTRY SITE OF HEPATITIS-C VIRUS

Chimeric genomes of poliovirus (PV) have been constructed in which the cognate internal ribosomal entry site (IRES) element was replaced by genetic elements of hepatitis C virus (HCV). Replacement of PV IRES wi th nt 9-332 of the genotype Ib HCV genome, a sequence comprising all b ut the first eight residues of the 5' nontranslated region (5'NTR) of HCV, resulted in a lethal phenotype. Addition of 366 nt of the HCV cor e-encoding sequence downstream of the HCV 5'NTR yielded a viable PV/HC V chimera, which expressed a stable, small-plaque phenotype, This chim eric genome encoded a truncated HCV core protein that was fused to the N terminus of the PV polyprotein via an engineered cleavage site for PV proteinase 3C(pro), Manipulation of the HCV core-encoding sequence of this viable chimera by deletion and frameshift yielded results sugg esting that the 5'-proximal sequences of the HCV open reading frame we re essential for viability of the chimera and that the N-terminal basi c region of the HCV core protein is required for efficient replication of the chimeric virus, These data suggest that the bona fide HCV IRES includes genetic information mapping to the 5'NTR and sequences of th e HCV open reading frame, PV chimeras replicating under translational control of genetic elements of HCV can serve to study HCV IRES functio n in vivo and to search for anti-HCV chemotherapeutic agents.