Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 129

Thirteen families of viruses containing ssDNA genomes have been recognized; the families Anelloviridae, Circoviridae, Genomoviridae, and Parvoviridae include viruses that infect vertebrates. ssDNA must be copied into mRNA before proteins can be produced. However, RNA can be made only from a dsDNA template, whatever the sense of the ssDNA. Consequently, DNA synthesis must precede mRNA production in the replication cycles of these viruses. All synthesis of viral DNA is catalyzed by cellular DNA polymerases.

Figure 3.2 Structure and expression of viral double-stranded DNA genomes. (A) Synthesis of genomes, mRNA (shown as green line in yellow box), and protein (shown as brown line). The icon represents a polyomavirus particle. (B to E) Genome configurations. Ori, origin of replication; ITR, inverted terminal repeat; TP, terminal protein; L, long region; S, short region; U_L and U_S, long and short unique regions; IRL, internal repeat sequence, long region; IRS, internal repeat sequence, short region; TRL, terminal repeat sequence, long region; TRS, terminal repeat sequence, short region; OriL, origin of replication of the long region; OriS, origin of replication of the short region.

Figure 3.3 Structure and expression of viral gapped, circular, double-stranded DNA genomes. (A) Synthesis of genome, mRNA, and protein. (B) Configuration of the hepadnavirus genome.