title: The ability of TNPO3-depleted cells to inhibit HIV-1 infection requires CPSF6.
abstract: BACKGROUND
  Expression of the cellular karyopherin TNPO3/transportin-SR2/Tnp3 is necessary for HIV-1 infection. Depletion of TNPO3 expression in mammalian cells inhibits HIV-1 infection after reverse transcription but prior to integration.
  
  
  RESULTS
  This work explores the role of cleavage and polyadenylation specificity factor subunit 6 (CPSF6) in the ability of TNPO3-depleted cells to inhibit HIV-1 infection. Our findings showed that depletion of TNPO3 expression inhibits HIV-1 infection, while the simultaneous depletion of TNPO3 and CPSF6 expression rescues HIV-1 infection. Several experiments to understand the rescue of infectivity by CPSF6 were performed. Our experiments revealed that the HIV-1 capsid binding ability of the endogenously expressed CPSF6 from TNPO3-depleted cells does not change when compared to CPSF6 from wild type cells. In agreement with our previous results, depletion of TNPO3 did not change the nuclear localization of CPSF6. Studies on the formation of 2-LRT circles during HIV-1 infection revealed that TNPO3-depleted cells are impaired in the integration process or exhibit a defect in the formation of 2-LTR circles. To understand whether the cytosolic fraction of CPSF6 is responsible for the inhibition of HIV-1 in TNPO3-depleted cells, we tested the ability of a cytosolic full-length CPSF6 to block HIV-1 infection. These results demonstrated that overexpression of a cytosolic full-length CPSF6 blocks HIV-1 infection at the nuclear import step. Fate of the capsid assays revealed that cytosolic expression of CPSF6 enhances stability of the HIV-1 core during infection.
  
  
  CONCLUSIONS
  These results suggested that inhibition of HIV-1 by TNPO3-depleted cells requires CPSF6.
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine Bronx, New York, NY 10461, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Fricke
authors.forename: Jose Carlos
authors.initials: JC
authors.lastname: Valle-Casuso
authors.forename: Tommy E
authors.initials: TE
authors.lastname: White
authors.forename: Alberto
authors.initials: A
authors.lastname: Brandariz-Nuñez
authors.forename: William J
authors.initials: WJ
authors.lastname: Bosche
authors.forename: Natalia
authors.initials: N
authors.lastname: Reszka
authors.forename: Robert
authors.initials: R
authors.lastname: Gorelick
authors.forename: Felipe
authors.initials: F
authors.lastname: Diaz-Griffero
mesh_terms: D002460:Cell Line; D015497:HIV-1 / Q000276:immunology* / Q000502:physiology*; D006801:Humans; D048348:Reverse Transcription; D016662:Virus Integration; D028961:beta Karyopherins / Q000378:metabolism*; D039221:mRNA Cleavage and Polyadenylation Factors / Q000378:metabolism*
chemical_list: C546476:TNPO3 protein, human; D028961:beta Karyopherins; C450562:cleavage factor Im, human; D039221:mRNA Cleavage and Polyadenylation Factors