Biology Reference
In-Depth Information
Introduction
Historically, viruses were assigned to the herpesvirus family based on the architec-
ture of their virions. Herpesvirus virions contain a linear double-stranded DNA
genome packaged in an icosahedral (T = 16) capsid. The capsid is surrounded by a
structured protein layer known as the tegument, and this, in turn, is enclosed in
a glycoprotein-containing lipid bilayer. The capsid of herpesviruses ranges from
approximately 115 to 130 nm in diameter, and the complete virion measures about
150-200 nm in diameter.
Biological criteria, such as host range and growth kinetics, were used to assign
the herpesviruses to three different subfamilies, the α-, β- and γ-herpesviruses.
These groupings have proven to accurately reflect the diversity in organization and
gene content of herpesvirus genomes as well. Herpesviruses that infect mammals
populate each of the subfamilies. Mammalian herpesviruses have genomes that
vary in size by a factor of about two. The α-herpesviruses have the smallest
genomes, γ-herpesviruses are intermediate in size and the β-herpesviruses are
Table 1
Sequenced members of the
β
-herpesvirus subfamily
Genome
GenBank accession
Virus
Genus
type/size
a
number
Viruses of humans
Human herpes virus 5
Cytomegalovirus
E/~235
AD169: X17403
(human cytomegalovirus)
AC146999
Towne: AC146851
Towne: AY315197
Toledo: AC146905
FIX:
AC146907
TR:
AC146904
PH:
AC146904
Merlin: AY446894
Human herpes virus 6A
Roseolovirus
A/~165
X83413
Human herpes virus 6B
Roseolovirus
A/~165
AB021506
AF157706
Human herpes virus 7
Roseolovirus
A/~145
AF037218
U43400
Viruses of nonhuman primates
Chimpanzee cytomegalovirus
Cytomegalovirus
E/~241
AF480884
Rhesus cytomegalovirus
Cytomegalovirus
F/~221
AY186194
DQ120516
Tree shrew herpesvirus
Unassigned
F/~196
AF281817
Viruses of rodents
Mouse cytomegalovirus Muromegalovirus A/~235 U68299
Rat cytomegalovirus Muromegalovirus A/~230 AF232689
a
The type of genome sequence arrangement (Pellet and Roizman 2006) and approximate size
(kbp) of the genome are indicated
