AIDS/HIV, Molecular and Cell Biology
105
R
U5 PB
gag
pol
env
U3
R
5
3
3
5
3
R
U5
3
PB
gag
pol
env
U3
R
5
3
R
U5
PB
gag
pol
env
U3
R
PB
gag
pol
env
U3
3
R
U5
PB
gag
pol
env
U3
3
R
U5
U3
PB
5'
3
R U5
U3
PB
5
3
R
U5
U3
PB
R U5 PB
gag
pol
env
U3
R
5
3
3
U3
U5
5
LTR
LTR
Fig. 5
Reverse transcription.
to the lack of RT proof-reading, produces
the remarkable sequence diversity seen
in HIV.
The DNA provirus is transported into
the nucleus as a preintegration complex
(PIC) using karyophilic signals found on
proteins with the complex including the
matrix protein, the integrase, and the Vpr
accessory protein. There is some func-
tional redundancy between these signals.
In lentiviruses, the PIC can cross an intact
nuclear membrane, meaning that these
viruses have the unique capability among
retroviruses of being able to integrate into
cells that are not undergoing mitosis.
The integration step involves the inte-
grase enzyme cleaving the cellular DNA
and making a 3
0
to 5
0
recess in the two
ends of the proviral DNA. The chromoso-
mal DNA undergoes a similar staggered
previous page 105 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online next page 107 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online Home Toggle text on/off