Investigating the mechanism of HSV-1 capsid maturation and virion assembly
Chi, Jung Hee Isabella
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Herpes simplex virus type 1 (HSV-1) consists of four morphologically distinct structures, the core, capsid, tegument, and envelope. The core is composed of a dsDNA genome packaged within an icosahedral capsid that is assembled in the nucleus of an infected host cell. The tegument and the envelope surround the capsid and are acquired at a later stage of viral infection in the cytoplasm.;Utilizing the reversible temperature sensitive HSV-1 mutant tsProt.A in the process of capsid assembly and maturation, we demonstrated that the expression of hexon specific 8F5/5C epitopes on capsids and recruitment of VP26 to the hexons followed the same kinetics in an ATP dependent manner. Thus, the process of 8F5/5C epitope generation may be driven by the recruitment of VP26 onto the tips of hexons.;Once capsids have matured and packaged the viral genome in the nucleus, they then enter the cytoplasm to acquire tegument and envelope. The molecular mechanism of cytoplasmic envelopment is unclear, but evidence suggests that the viral glycoprotein tails may play an important role in the recruitment of tegument and capsids to the site of final envelopment.;Using a GST binding assay, we examined the role of the cytoplasmic tail of viral glycoprotein D. This study demonstrated that a 38-kDa tegument protein VP22 and capsids bound specifically to the gD tail. Alanine scanning mutagenesis revealed that these interactions were dependent on arginine and lysine residues, at positions 5 and 6, respectively in the tail.