Biology Reference
In-Depth Information
As non-enveloped viruses lack a membrane bilayer, they cannot fuse
with a cellular membrane to deliver their genome or modified viral par-
ticles into the cytoplasm of the host cell. Thus, two potential mecha-
nisms for membrane penetration of non-enveloped viruses have been
proposed: (1) virus-induced membrane rupture and (2) selective
genome translocation across a cellular membrane through pores formed
by viral proteins (Fig. 6). The first mechanism (Fig. 6A) is well charac-
terized for adenovirus, a DNA virus.
82
Adenovirus enters cells by recep-
tor-mediated, clathrin-dependent endocytosis. The viral protease is
activated within the reductive environment of endosomes. This results
Fig. 6.
Analysis of the mechanism of uncoating and penetration of non-
enveloped viruses by endosome rupture or by pore formation. (
A
) Endosome
rupture of adenovirus, for example, results in release of co-internalized fluid-
phase marker into the cytosol. Fluid-phase markers of low and high molecu-
lar mass are lost from the endosomes to a similar extent. (
B
) Formation of
virus-induced pores results in loss of low but not of high molecular mass
markers from otherwise intact endosomes. It is assumed that the minor group
HRV genome is transferred into the cytosol via such a size-restricting pore.
