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UL
US
a
TRL
IRL IRS
TRS
a
b
b
a
c
c
a
ori-L
ori-S
ori-S
Infection
a a'
b
a a'
c
Replication
a' US a UL a' US a UL a'
US a
(150 kbp)
concatemers
concatemers
(150 kbp)
(150 kbp)
(150 kbp)
a a'
Encapsidation
a' US a UL a' a' US a UL a'
US a
a
Procapsid
a'
a
a'
Capsid
Fig. 2
Replication of the HSV-1 genome. (
a
) The double-stranded (ds) viral DNA
is composed of two unique sequences, designated as unique long (UL) and
unique short (US), surrounded by terminal (TRS) and internal (IRS) repeated
sequences. The repeated inverted sequences
a
and
a
(
black rectangles
) contain
the cleavage/packaging sequence signals. The repeated inverted sequences
b
and
b
′
and
c
are denoted by
grey rectangles
. The virus genome contains
three origins of viral DNA synthesis (
black circles
), one located in the middle of
UL (oriL) and two in the repeated sequences
c
and
c
′
and
c
′
that surround US (oriS).
(
b
) Immediately after entry into the nucleus, the virus DNA circularizes. (
c
) The
circular viral DNA initiates bidirectional replication that is rapidly converted,
probably by recombination between the repeated sequences, into a rolling circle
like mechanism. The newly synthesized long concatemeric viral DNA is then
cleaved at signals
a
or
a
′
allowing the genomic units to become packaged into
preformed empty capsids, thus producing mature intranuclear capsids that are
then translocated into the cytoplasm where they will acquire the tegument and
the envelope
′
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