Herpesvirus Genome: Important Properties

+ Linear, double-stranded DNA

+ Monopartite

+ DNA wrapped around a fibrillar spool which makes up the core

+ *A unique feature*: reiterated DNA sequences
(i) At the ends
(ii) Some herpesviruses have internal repeats which divide the genome into unique short (US) and unique long (UL) sequences.
(iii) These repeats can invert to give rise to up to four different isomers of a genome, which present in equimolar proportions.

+ *Another unique feature*: Herpesviruses themselves encode most of the enzymes that they require to replicate viral DNA.
Scientists hypothesize that this allows the virus to replicate in slowly-dividing or non-dividing cells such as neurons.
e.g. For HSV, about 50% of its 73 genes are not critical for viral replication in vitro. The other genes may encode regulatory proteins and virokines to help with in vivo pathogenesis.

Size of Genomes

HSV (type 1 and type2)152 kilobases
VZV 125 kb
EBV 172 kb
CMV 229 kb
HHV-6 162 kb


Created: March 4, 1999
Last modified: March 4, 1999