Assembly and release
Heinrich G. Göttlinger and Winfried Weissenhorn
from: Retroviruses: Molecular Biology, Genomics and Pathogenesis (Edited by: Reinhard Kurth and Norbert Bannert). Caister Academic Press, U.K. (2010)
Retroviral assembly and release are both mediated by the viral Gag polyprotein. Proteolytic processing of Gag within the immature virus particle yields the internal structural proteins of the mature virion, of which matrix (MA), capsid (CA), and nucleocapsid (NC) are common to all retroviruses. Within the context of the unprocessed polyprotein, the MA domain is primarily required for Gag membrane targeting and for the incorporation of the viral surface glycoproteins into progeny virions. The CA domain of Gag provides the major driving force for the assembly of immature particles. After rearranging into a different type of lattice subsequent to the proteolytic processing of Gag, CA forms the core of the mature virion. NC nucleates immature particle assembly through the concentration of Gag on RNA molecules, and also plays an essential role in the encapsidation of the viral RNA genome. Retroviral Gag proteins also harbour conserved motifs that co-opt a cellular budding machinery to promote the separation of the lipid envelope of the nascent virion from the cell surface, and thus the release of an extracellular virion. The distinct roles of the various Gag domains in virus morphogenesis are the subject of this review read more ...