Nucleic Acid Packaging in Viruses.

Viruses shield their genetic information by enclosing the viral nucleic acid inside a protein shell (capsid), in a process known as genome packaging. Viruses follow essentially two main strategies to package their genome: Either they co-assemble their genetic material together with the capsid protein or an empty shell (procapsid) is first assembled and then the genome is pumped inside the capsid by a molecular motor that uses the energy released by ATP hydrolysis. During packaging the viral nucleic acid is highly condensed through a meticulous arrangement in concentric layers inside the capsid. In this chapter we will first give an overview of the different strategies used for genome packaging to discuss later some specific virus models where the structures of the main proteins involved are presented and the biophysics underlying the packaging mechanism are discussed.