Viruses safeguard their genetic material by encasing the viral nucleic acid within a protein shell (capsid), a process known as genome packing. The viral nucleic acid (DNA or RNA) contains the genetic instructions for protein synthesis in order to create new viruses, i.e. the virus's genome. When a virus identifies a target cell, the nucleic acid is transferred into it.
The virus composition is made up of three major components: nucleic acid, capsid, and envelope. A virus's nucleic acid is located within its inner core and includes the genetic material for protein synthesis and replication. Viruses' hereditary substance can be single-stranded or double-stranded DNA or RNA. When a virus infects a recipient cell, the nucleic acid is replicated.transferred into the recipient cell. The viral nucleic acid enters the nucleus and directs the cell to create proteins that are assembled to produce more virus cells.
Viruses safeguard their genetic material by enclosing the viral nucleic acid inside a protein shell (capsid), a process known as genome packaging. Viruses package their genome in one of two ways: either they co-assemble their genetic material with the capsid protein, or they first build an empty casing (procapsid) and then pump the genome inside the capsid with a molecular engine powered by ATP hydrolysis. During packing, the viral nucleic acid is concentrated to a very high quantity by carefully arranging it in concentric layers inside the capsid. In this part, we will discussfirst 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, and the biophysics underlying the packaging mechanism, have been well documented.