INTERACTION OF POLY(RC) BINDING-PROTEIN-2 WITH THE 5' NONCODING REGION OF HEPATITIS-A VIRUS-RNA AND ITS EFFECTS ON TRANSLATION

Utilization of internal ribosome entry segment (IRES) structures in th e 5' noncoding region (5'NCR) of piconavirus RNAs for initiation of tr anslation requires a number of host cell factors whose distribution ma y vary in different cells and whose requirement may vary for different picornaviruses. We have examined the requirement of the cellular prot ein poly(rC) binding protein 2 (PCBP2) for hepatitis A virus (HAV) RNA translation. PCBP2 has recently been identified as a factor required for translation and replication of poliovirus (PV) RNA. PCBP2 was show n to be present in FRhK-4 cells, which are permissive for growth of HA V, as it is in HeLa cells, which support translation of HAV RNA but wh ich have not been reported to host replication of the virus. Competiti on RNA mobility shift assays showed that the 5'NCR of HAV RNA competed for binding of PCBP2 with a probe representing stem-loop IV of the PV 5'NCR. The binding site on HAV RNA was mapped to nucleotides 1 to 157 , which includes a pyrimidine-rich sequence. HeLa cell extracts that h ad been depleted of PCBP2 by passage over a PV stem-loop IV RNA affini ty column supported only low levels of HAV RNA translation. Translatio n activity was restored upon addition of recombinant PCBP2 to the depl eted extract. Removal of the 5'-terminal 138 nucleotides of the HAV RN A, or removal of the entire IRES, eliminated the dependence of HAV RNA translation on PCBP2.