Oligomeric structures of poliovirus polymerase are important for function

Central to the replication of poliovirus and other positive-strand RNA viru ses is the virally encoded RNA-dependent RNA polymerase. Previous biochemic al studies have suggested that direct polymerase-polymerase interactions mi ght be important for polymerase function, and the structure of poliovirus p olymerase has revealed two regions of extensive polymerase-polymerase inter action. To explore potential functional roles for the structurally observed polymerase-polymerase interactions, we have performed RNA binding and exte nsion studies of mutant polymerase proteins in solution, disulfide cross-li nking studies, mutational analyses in cells, ill vitro activity analyses an d RNA substrate modeling studies. The results of these studies indicate tha t both regions of polymerase-polymerase interaction observed in the crystal s are indeed functionally important and, furthermore, reveal specific funct ional roles for each. One of the two regions of interaction provides for ef ficient substrate RNA binding and the second is crucial for forming catalyt ic sites. These studies strongly support the hypothesis that the polymerase -polymerase interactions discovered in the crystal structure provide an exq uisitely detailed structural context for poliovirus polymerase function and for poliovirus RNA replication in cells.