INHIBITION OF PARVOVIRUS MINUTE VIRUS OF MICE REPLICATION BY A PEPTIDE INVOLVED IN THE OLIGOMERIZATION OF NONSTRUCTURAL PROTEIN NS1

The large nonstructural protein NS1 of the minute virus of mice and ot her parvoviruses is involved in essential steps of the viral life cycl e, such as DNA replication and transcriptional regulation, and is a ma jor contributor to the toxic effect on host cells. Various biochemical functions, such as ATP binding, ATPase, site-specific DNA binding and nicking, and helicase activities, have been assigned to NS1. Homo-oli gomerization is a prerequisite for a number of proteins to be fully fu nctional. In particular, helicases generally act as homo-oligomers. In direct evidence of NS1 self-association has been recently obtained by a nuclear cotransport assay (J. P, Nuesch and P. Tattersall, Virology 196:637-651, 1993). In order to demonstrate the oligomerizing property of NS1 in a direct way and localize the protein region(s) involved, t he yeast two-hybrid system was used in combination with deletion mutag enesis across the whole NS1 molecule, followed by high-resolution mapp ing of the homo-oligomerization domain by a peptide enzyme-linked immu nosorbent assay method. This study led to the identification of a dist inct NS1 peptide that contains a bipartite domain involved in NS1 olig omerization. Furthermore, this isolated peptide was found to act as a specific competitive inhibitor and suppress NS1 helicase activity in v itro and parvovirus DNA replication in vivo, arguing for the involveme nt of NS1 oligomerization in these processes. Our results point to dru g targeting of oligomerization motifs of viral regulatory proteins as a potentially useful antiviral strategy.