Interaction between cauliflower mosaic virus inclusion body protein and capsid protein: implications for viral assembly.

The cauliflower mosaic virus (CaMV) inclusion body protein (pVI) is able to specifically interact with the viral capsid precursor protein (pIV). By using the yeast two-hybrid system and a blot assay, the pIV region required for the recognition of pVI was mapped to the lysine-rich domain. This region of only 48 amino acids when fused to dihydrofolate reductase (DHFR) mediated pVI and DNA binding in vitro. Competition experiments confirmed that pVI and DNA bind to the same region of pIV. Since pVI is absent from the mature virus, models are discussed in which pVI plays an accessory role in CaMV assembly, in addition to its function in transactivating translation.