Transportin-SR2 imports HIV into the nucleus.
BACKGROUND
The human immunodeficiency virus type 1 (HIV-1) and other lentiviruses have the capacity to infect nondividing cells like macrophages. This requires import of the preintegration complex (PIC) through the nuclear pore. Although many cellular and viral determinants have been proposed, the mechanism leading to nuclear import is not yet understood.


RESULTS
Using yeast two-hybrid and pull-down, we identified and validated transportin-SR2 (TRN-SR2) as a bona fide binding partner of HIV-1 integrase. We confirmed the biological relevance of this interaction by RNAi. Depletion of TRN-SR2 interfered with the replication of HIV-1 and HIV-2 but not MoMLV in HeLaP4 cells. Knockdown of TRN-SR2 in primary macrophages likewise interfered with HIV-1 replication. Using Q-PCR, we pinpoint this block in replication to the early steps of the viral lifecycle. A reduction in 2-LTR formation suggests a block in PIC nuclear import upon siRNA-mediated knockdown. Different lines of evidence clearly proved that the late steps of viral replication are not affected. In an in vivo nuclear-import assay using labeled HIV-1 particles, the defect in nuclear import after depletion of TRN-SR2 was directly visualized. In comparison with control cell lines, the great majority of siRNA-treated cells did not contain any PIC in the nucleus.


CONCLUSIONS
Our data clearly demonstrate that TRN-SR2 is the nuclear-import factor of HIV.
Christ
Frauke
F
Laboratory for Molecular Virology and Gene Therapy, KU Leuven and IRC, Kapucijnenvoer 33, B-3000 Leuven, Flanders, Belgium.
Thys
Wannes
W
De Rijck
Jan
J
Gijsbers
Rik
R
Albanese
Alberto
A
Arosio
Daniele
D
Emiliani
Stephane
S
Rain
Jean-Christophe
JC
Benarous
Richard
R
Cereseto
Anna
A
Debyser
Zeger
Z
D002467:Cell Nucleus / Q000378:metabolism / Q000821:virology*; D015658:HIV Infections / Q000821:virology; D019427:HIV Integrase / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism* / Q000502:physiology; D020798:Two-Hybrid System Techniques; D014779:Virus Replication; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*
D028961:beta Karyopherins; C424165:transportin SR2; D019427:HIV Integrase; C514801:p31 integrase protein, Human immunodeficiency virus 1