HIV-1 exploits importin 7 to maximize nuclear import of its DNA genome.
BACKGROUND
Nuclear import of the HIV-1 reverse transcription complex (RTC) is critical for infection of non dividing cells, and importin 7 (imp7) has been implicated in this process. To further characterize the function of imp7 in HIV-1 replication we generated cell lines stably depleted for imp7 and used them in conjunction with infection, cellular fractionation and pull-down assays.


RESULTS
Imp7 depletion impaired HIV-1 infection but did not significantly affect HIV-2, simian immunodeficiency virus (SIVmac), or equine infectious anemia virus (EIAV). The lentiviral dependence on imp7 closely correlated with binding of the respective integrase proteins to imp7. HIV-1 RTC associated with nuclei of infected cells with remarkable speed and knock down of imp7 reduced HIV-1 DNA nuclear accumulation, delaying infection. Using an HIV-1 mutant deficient for reverse transcription, we found that viral RNA accumulated within nuclei of infected cells, indicating that reverse transcription is not absolutely required for nuclear import. Depletion of imp7 impacted on HIV-1 DNA but not RNA nuclear import and also inhibited DNA transfection efficiency.


CONCLUSIONS
Although imp7 may not be essential for HIV-1 infection, our results suggest that imp7 facilitates nuclear trafficking of DNA and that HIV-1 exploits imp7 to maximize nuclear import of its DNA genome. Lentiviruses other than HIV-1 may have evolved to use alternative nuclear import receptors to the same end.
Zaitseva
Lyubov
L
Wohl Virion Centre, Division of Infection and Immunity, University College London, London, UK.
Cherepanov
Peter
P
Leyens
Lada
L
Wilson
Sam J
SJ
Rasaiyaah
Jane
J
Fassati
Ariberto
A
D021581:Active Transport, Cell Nucleus; D002460:Cell Line; D002467:Cell Nucleus / Q000821:virology; D004279:DNA, Viral / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000378:metabolism; D019427:HIV Integrase / Q000378:metabolism; D015497:HIV-1 / Q000502:physiology*; D015498:HIV-2 / Q000502:physiology; D006801:Humans; D004860:Infectious Anemia Virus, Equine / Q000502:physiology; D028884:Karyopherins / Q000378:metabolism*; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015302:Simian Immunodeficiency Virus / Q000502:physiology; D014779:Virus Replication
D004279:DNA, Viral; C466996:IPO7 protein, human; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D019427:HIV Integrase; D004706:Endodeoxyribonucleases; C058608:endonuclease-integrase