Phosphorylation of cucumber mosaic virus RNA polymerase 2a protein inhibits formation of replicase complex.

The 2a (polymerase) protein of cucumber mosaic virus (CMV) was shown to be phosphorytated both in vivo and in vitro. In vitro assays using 2a protein mutants and tobacco protein kinases showed that the 2a protein has at least three phosphorylation sites, one of which is located within the N-terminal 126 amino acid region. This region is essential and sufficient for interaction with the CMV la protein. When phosphorylated in vitro, the 2a protein N-terminal region failed to interact with the la protein. Since the la-2a interaction is essential for the replication of CMV, this suggests that phosphorytation of the N-terminal region of the 2a protein negatively modulates the interaction in vivo, and may have a regulatory rote acting directly in viral infection. [ABSTRACT FROM AUTHOR]