Interaction of poly(rC)-binding protein 2 with the 5 '-terminal stem-loop of the hepatitis C virus genome

The 5' noncoding region (NCR) of hepatitis C virus (HCV) contains an intern al ribosome entry site for translation initiation. Cellular proteins (e.g. La, polypyrimidine tract-binding protein, and p25) that interact with HCV 5 ' NCR have been implicated in facilitating efficient internal initiation. T he 5' NCR may also contain RNA structures and specific RNA sequences that i nteract with cellular proteins to promote RNA replication. UV crosslinking experiments revealed a 43-kDa cellular protein (p43) also interacts with th e HCV 5' NCR. Further UV crosslinking experiments with deletion mutants of HCV 5' NCR demonstrated that p43 bound specifically to the 5'-terminal stem -loop of the HCV 5' NCR. Achromobactor proteinase I digests, competition ex periments, and immunoprecipitation confirmed that p43 was identical to huma n poly(rC)-binding protein 2 (PCBP2). We prepared a PCBP2-immunodepleted ra bbit reticulocyte lysate with an anti-PCBP2 antibody. Translation activity promoted by the HCV internal ribosome-entry site was the same in PCBP2-depl eted lysates as in mock-depleted lysates. In conclusion, PCBP2 specifically interacted with the 5' terminus of HCV genome but had no effect on HCV tra nslation. We speculate that PCBP2's interaction with HCV 5' NCR may be invo lved in the replication-initiation complex of HCV. (C) 2001 Elsevier Scienc e B.V. All rights reserved.