Interaction of the Cauliflower mosaic virus coat protein with the pregenomic RNA leader

Using the yeast three-hybrid system, the interaction of the Cauliflower mos aic virus (CaMV) pregenomic 35S RNA (pgRNA) leader with the viral coat prot ein, its precursor,land a series of derivatives was studied. The purine-ric h domain in the center of the pgRNA leader was found to specifically intera ct with the coat protein. The zinc finger motif of the coat protein and the preceding basic domain were essential for this interaction. Removal of the N-terminal portion of the basic domain led to loss of specificity but did not affect the strength of the interaction. Mutations of the zinc finger mo tif abolished not only the interaction with the RNA but also viral infectiv ity. In the presence of the very acidic C-terminal domain, which is part of the preprotein but is not present in the mature CP, the interaction with t he RNA was undetectable.