FIG. 12.

Comparison of the expression strategies and regulation of replication of different members of the alpha-like supergroup of viruses. Shown is a schematic representation of the nonstructural replication proteins of TYMV, SIN, and RUB. Protein domains are designated as in Fig. 1. Cleavage sites are represented by filled triangles. The number below each cleavage site indicates the sequential order of the cleavage in the precursor protein. Cleavages that are required for minus-strand RNA synthesis are filled in black, whereas those required for switching from minus- to plus-strand synthesis are filled in gray.