1-31-07

REPLICATION OF dsDNA GENOME VIRUSES
B. Poxviruses

The poxviruses have the largest virions among all viruses, containing a large dsDNA genome (roughly the same genome size range as the herpesviruses). Variola virus (smallpox) and Vaccinia virus (the vaccine against smallpox) have a genome size of about 190 Kbp, coding for about 180 proteins (about 150 of which are very similar between smallpox and vaccinia).

1. What are the general features of the replication cycle of the Poxviruses?

The poxviruses are the only DNA genome viruses that replicate and express their genome in the cytoplasm (rather than in the nucleus) of the infected cell. This implies that the viral genome must code for essentially all the enzymes needed for DNA replication and transcription, and moreover that several specific enzymes must actually be in the virion, and enter the cell along with the genome, to get viral gene expression started. We will expand on the following basic figure.


 

2. What do we know about the assembly and release of new poxvirus virions?

In 2002, the Journal of General Virology had a review article (Smith et al.) entitled "The formation and function of extracellular enveloped vaccinia virus". See Figure 1 in this review for an overview of what is known concerning the final stages of poxvirus assembly and release.

 


3. What is a 2006 update on the entry process?

Here's an April 2006 article in Proc. Nat. Acad. Sci.: "Ligand-induced and nonfusogenic dissolution of a viral membrane."

 

4. What's an example of a late 2006 journal article on poxvirus replication?

Here's a December 2006 article in Proc. Nat. Acad. Sci.: "Existence of an operative pathway from the endoplasmic reticulum to the immature poxvirus membrane."