HIV-1 capsid is involved in post-nuclear entry steps.
BACKGROUND
HIV-1 capsid influences viral uncoating and nuclear import. Some capsid is detected in the nucleus but it is unclear if it has any function. We reported that the antibiotic Coumermycin-A1 (C-A1) inhibits HIV-1 integration and that a capsid mutation confers resistance to C-A1, suggesting that capsid might affect post-nuclear entry steps.


RESULTS
Here we report that C-A1 inhibits HIV-1 integration in a capsid-dependent way. Using molecular docking, we identify an extended binding pocket delimited by two adjacent capsid monomers where C-A1 is predicted to bind. Isothermal titration calorimetry confirmed that C-A1 binds to hexameric capsid. Cyclosporine washout assays in Jurkat CD4+ T cells expressing engineered human TRIMCyp showed that C-A1 causes faster and greater escape from TRIMCyp restriction. Sub-cellular fractionation showed that small amounts of capsid accumulated in the nuclei of infected cells and C-A1 reduced the nuclear capsid. A105S and N74D capsid mutant viruses did not accumulate capsid in the nucleus, irrespective of C-A1 treatment. Depletion of Nup153, a nucleoporin located at the nuclear side of the nuclear pore that binds to HIV-1 capsid, made the virus less susceptible to TRIMCyp restriction, suggesting that Nup153 may help maintain some integrity of the viral core in the nucleus. Furthermore C-A1 increased binding of CPSF6, a nuclear protein, to capsid.


CONCLUSIONS
Our results indicate that capsid is involved in post-nuclear entry steps preceding integration.
Division of Infection and Immunity, University College London, Cruciform Building, 90 Gower Street, London, WC1E 6BT, UK.|Division of Infectious Diseases, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, 5 Fuhsing Street, Kueishan, Taoyuan, 333, Taiwan.
Nan-Yu
NY
Chen
Division of Infection and Immunity, University College London, Cruciform Building, 90 Gower Street, London, WC1E 6BT, UK.|Genome Damage and Stability Centre, University of Sussex, Science Park Road, Falmer, Brighton, BN1 9RQ, UK.
Lihong
L
Zhou
Medicinal Chemistry Group, University College London, Cruciform Building, Gower Street, London, WC1E 6BT, UK.|Chemical Computing Group, St. John's Innovation Centre, Cowley Road, Cambridge, CB4 0WS, UK.
Paul J
PJ
Gane
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
Silvana
S
Opp
Mill Hill Laboratory, The Francis Crick Institute, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
Neil J
NJ
Ball
Mill Hill Laboratory, The Francis Crick Institute, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
Giuseppe
G
Nicastro
Department of Microbiology and Molecular Medicine, University of Geneva, 1 Rue Michel Servet, CH-1211, Geneva, Switzerland.|Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Biotech 2, Suite 319, Worcester, MA, 01605, USA.
Madeleine
M
Zufferey
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
Cindy
C
Buffone
Department of Microbiology and Molecular Medicine, University of Geneva, 1 Rue Michel Servet, CH-1211, Geneva, Switzerland.|Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Biotech 2, Suite 319, Worcester, MA, 01605, USA.|Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 373 Plantation Street, Biotech 2, Suite 319, Worcester, MA, 01605, USA.
Jeremy
J
Luban
Medicinal Chemistry Group, University College London, Cruciform Building, Gower Street, London, WC1E 6BT, UK.
David
D
Selwood
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
Felipe
F
Diaz-Griffero
Mill Hill Laboratory, The Francis Crick Institute, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
Ian
I
Taylor
Division of Infection and Immunity, University College London, Cruciform Building, 90 Gower Street, London, WC1E 6BT, UK. a.fassati@ucl.ac.uk.
Ariberto
A
Fassati
D049933:Aminocoumarins / Q000378:metabolism; D000998:Antiviral Agents / Q000378:metabolism; D002460:Cell Line; D016655:HIV Core Protein p24 / Q000378:metabolism*; D015497:HIV-1 / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D053586:Virus Internalization
D049933:Aminocoumarins; D000998:Antiviral Agents; D016655:HIV Core Protein p24; C004628:coumermycin
Capsid; Coumermycin-A1; HIV-1; Integration; Nucleoporins; Nucleus; Nup153; Uncoating