Figure 1. General stages in viral replicative cycles. The main stages constituting the replicative cycle of a DNA virus are depicted. In the case of plant DNA viruses, there is a cell wall that imposes restrictions on viral release. In this case, it is also important that intercellular movement of viral particles is achieved through the plasmodesmata, unique structures that allow communication between the cytoplasm of neighbouring plant cells. Early/late gene expression (transcription) and the DNA replication stages can occur either in the cytoplasm (poxviruses) or in the nucleus of the infected cell.

Figure 2. Strategies of transcriptional genomic organization of different DNA virus families. Examples are given for viruses with a single-stranded DNA genome, either (a) linear (Parvoviridae, genus Dependovirus) or (b) circular (Geminiviridae, genus Mastrevirus), and with a double-stranded DNA genome, either (c) linear (Adenoviridae, genus Mastadenovirus) or (d) circular (Papovaviridae, genus Polyomavirus). Messenger RNA transcripts are indicated by arrows, with the arrowhead at the 3¢-terminus and the spliced-out intron sequences shown by angled thin lines. See text for details.

Figure 3. Strategies for initiation of translation in DNA viruses. A bicistronic capped (black square) RNA containing two open reading frames (ORF1 and ORF2) is depicted. In addition to the standard scanning process to start translation, two other mechanisms (ribosome shunting and leaky scanning) are used by different DNA viruses to control translation of various viral ORFs. See text for details.

Figure 4. General steps during virus DNA replication.