Comparative investigations on the coat protein binding sites of the genomic RNAs of alfalfa mosaic and tobacco streak viruses

The genomic RNAs of alfalfa mosaic virus (AIMV) and tobacco streak virus (TSV) form complexes with viral coat protein. These complexes were subjected to digestion with ribonuclease T1 and filtered onto Millipore filters. It was shown that the major coat protein binding sites are located at the 3' ends of the genomic RNA species of AIMV and TSV in both heterologous and homologous RNA-coat protein combinations. Internal coat protein binding sites were found as well. Although there is homology between the 3'-terminal sequences, no structural features could be observed that are common to all coat protein binding sites. The fact that TSV and AIMV coat protein can mutually activate each others genome combined with the fact that the major target site of both coat protein preparations is located at the 3' ends of the genomic RNAs favors the assumption that binding of the coat protein to the 3' ends is an initiation event of the replication cycle.