HSV-1 model structure and genome arrangement. (a) The icosahedral, DNA-containing capsid is asymmetrically located within the virion and surrounded by an amorphous protein layer called the tegument, and a membrane envelope heterogeneously studded with morphologically distinct spikes formed by 12 different glycoprotein species. (b) The HSV-1 genome arrangement showing repeats surrounding UL designated ab and b′a′, and those surrounding US designated a′c′ and ca. There are two different origins of replication, oriL in the long segment and oriS in the short segment. Abbreviations: UL: long unique sequence; US: short unique sequence; TRL: terminal repeats of long segment; TRS: terminal repeats of short segment; IRL: internal repeat of the long segment; IRS: internal repeat of short segment.
