Fig. 14.18

Genome organization and replication of togaviruses. (a) Sindbis virus. (b) Rubella virus. The RNA genomes encode a single version (rubella virus) or two versions of the non-structural polyprotein as well as one structural polyprotein. First, the precursor of the non-structural proteins is synthesized and autocatalytically cleaved into the individual components by the intrinsic protease activity of the polyprotein. As a result, RNA-dependent RNA polymerase is generated, which uses the positive-sense RNA genome as a template and synthesizes a negative-sense RNA. This in turn serves as a template for the synthesis of both new positive-sense RNA genomes and subgenomic RNA molecules. The latter is used as mRNA for translation of the polyprotein for the structural components and which is processed into the various individual components by the activity of cellular signalases. Appr-1 protein domain with homology to the cellular protein ADP-ribose 1-monophosphate processing enzyme, aa amino acids, M/G transferase methyltransferase/guanylyltransferase, NSP non-structural protein