Nucleocapsid Structure, Assembly and DNA Packaging of Herpes Simplex Virus
James F. Conway and Fred L. Homa
from: Alphaherpesviruses: Molecular Virology (Edited by: Sandra K. Weller). Caister Academic Press, U.K. (2011)
The herpes simplex virion consists of an external membrane envelope, a proteinaceous layer called the tegument, and an icosahedral capsid containing the double-stranded linear DNA genome. The capsid shell is 125 nm in diameter and consists of 162 capsomers (150 hexons, 11 pentons and a portal) which lie on a T=16 icosahedral lattice. The capsid shell consists of four major structural proteins VP5, VP19C, VP23 and VP26 which are the products of the HSV UL19, UL38, UL18 and UL35 genes. In addition to the four major structural proteins the HSV-1 capsid contains a number of minor capsid proteins. These include the UL6, UL15, UL17, UL25, UL28 and UL33 proteins, all of which (along with the HSV-1 UL32 protein) are required for the processing and packaging of replicated viral DNA into preformed capsid shells. The UL6, UL17, UL25 and UL33 proteins remain associated with DNA containing capsids while UL15 and UL28 do not. This review is a summary of our present knowledge with respect to how the capsid is assembled, how DNA is packaged and what is known about the role of the seven packaging proteins in this process. In addition, recent advances in our understanding the structure of the four distinct types of capsids that are present in HSV infected cells as determined by three dimensional image reconstructions from cryo-electron microscopy (cryoEM) will be presented and discussed read more ...