title: Anti-HIV-1 activity of the G-quadruplex ligand BRACO-19.
abstract: OBJECTIVE
  A dynamic G-quadruplex region has been previously shown to form in the long terminal repeat (LTR) promoter of the HIV-1 integrated DNA genome. Inhibition of promoter activity and antiviral effects have been observed when this region was stabilized by BRACO-19, a trisubstituted acridine derivative that binds G-quadruplexes. Here, we aimed at characterizing the antiviral mechanism of action of BRACO-19 by analysing its activity towards a broad range of HIV-1 strains, host cells and infection modes.
  
  
  METHODS
  The antiviral activity of BRACO-19 in cell lines and primary cells infected or persistently infected by HIV-1 strains was evaluated at different times post-infection. Virucidal, viral binding, time-dependent and drug-dependent assays were performed to identify the viral target step. Circular dichroism, UV spectroscopy and a reverse transcriptase (RT) stop assay were used to assess RNA G-quadruplex folding and inhibition of RT processing.
  
  
  RESULTS
  Thorough virological assays demonstrated that BRACO-19 acts both at the reverse transcription and the post-integration level during the virus life cycle. This behaviour was rationalized by the observation that a G-quadruplex-forming sequence identical to that of the LTR DNA is present at the 3'-end of the virus RNA genome. Biophysics and biomolecular testing showed that this region has the ability to fold into very stable G-quadruplex structures that are even more stabilized by BRACO-19, therefore inhibiting the reverse transcription process at the template level.
  
  
  CONCLUSIONS
  Our findings strongly support the activity of BRACO-19 at the viral G-quadruplex level and therefore strengthen the use of viral G-quadruplexes as new anti-HIV-1 targets.
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy.
authors.forename: Rosalba
authors.initials: R
authors.lastname: Perrone
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Butovskaya
authors.affiliation: Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Daelemans
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Palù
authors.affiliation: Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Christophe
authors.initials: C
authors.lastname: Pannecouque
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy sara.richter@unipd.it.
authors.forename: Sara N
authors.initials: SN
authors.lastname: Richter
mesh_terms: D000166:Acridines / Q000494:pharmacology*; D019380:Anti-HIV Agents / Q000494:pharmacology*; D054856:G-Quadruplexes / Q000187:drug effects*; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D011533:Proviruses / Q000187:drug effects; D012367:RNA, Viral / Q000187:drug effects*; D048348:Reverse Transcription / Q000187:drug effects
chemical_list: D000166:Acridines; D019380:Anti-HIV Agents; D012367:RNA, Viral; C454064:BRACO-19
keywords: G-quadruplex RNA; antiviral activity; nucleic acid secondary conformation; small molecule; time of addition