MAIZE STREAK VIRUS COAT PROTEIN BINDS SINGLE-STRANDED AND DOUBLE-STRANDED DNA IN-VITRO

Maize streak virus (MSV) coat protein (CP) is required for virus movem ent within the plant. Deletion or mutation of MSV CP does not prevent virus replication in single cells or protoplasts but leads to a loss o f infectivity in the inoculated plant. The mechanism by which MSV CP m ediates the transfer of MSV DNA from cell to cell and through the vasc ular bundle is still unknown. Towards understanding the role of MSV CP in virus movement, the interaction of the CP with viral DNA was inves tigated using the 'south-western' assay. Wild-type and truncated MSV C Ps were expressed in E. coli and the expressed CPs were used to invest igate interactions with single-stranded (ss) and double-stranded (ds) DNA. The results showed that MSV CP bound ss and ds viral and plasmid DNA in a sequence non-specific manner. The binding domain was mapped t o within the 104 N-terminal amino acids of the MSV CP. We propose that the binding of CP to MSV DNA is involved in viral DNA nuclear transpo rt as well as encapsidation and thus may have a role in intra- and int er-cellular movement as well as systemic infection.