Mapping of protein domains of hepatitis A virus 3AB essential for interaction with 3CD and viral RNA

The small hydrophobic protein 3AB of the picornaviruses, encompassing the r eplication primer 3B, has been suggested to anchor the viral replication co mplex to membranes. For hepatitis A virus (HAV) 3AB, we have previously dem onstrated its ability to form stable homodimers, to bind to membranes, and to interact specifically with RNA, implicating its multiple involvement in viral replication. In the present report, we show that HAV 3AB additionally interacts with HAV protein sop, a feature also described for the correspon ding polypeptide of poliovirus. By assessing the interactions of three dele tion mutants, distinct domains of HAV 3AB were mapped. The hydrophobic doma in and the 3B moiety were found to be essential for the 3AB interaction wit h 3CD. Both electrostatic and hydrophobic forces are involved in this inter action. The cluster of charged amino acid residues at the C terminus of 3A seems to determine the specificity of 3AB interaction with RNA structures f ormed at either terminus of the HAV genome. Furthermore, our data implicate that 3A can interact with HAV RNA. Compared with poliovirus 3AB, which by itself is a nonspecific RNA-binding protein, HAV 3AB specifically recognize s HAV RNA structures that might be of relevance for initiation of viral RNA replication, (C) 1999 Academic Press.