title: A tryptophan-rich hexapeptide inhibits nucleic acid destabilization chaperoned by the HIV-1 nucleocapsid protein.
abstract: The nucleocapsid protein (NC) of HIV-1 exerts critical functions in viral genome replication and virus assembly. Since the recognition of target nucleic acids is required in the initial step of most NC-mediated processes, attempts were made to find small molecules capable of competing with this recognition. In particular, several Trp-rich hexapeptides were recently found to strongly bind RNA sequences targeted by NC. To further validate these peptides as potential anti-NC agents, we studied the ability of Ac-HKWPWW-NH2, taken as a representative, to interfere with the NC chaperone properties required during reverse transcription. Using NMR and steady-state and time-resolved fluorescence spectroscopy, we characterized the structure of Ac-HKWPWW-NH2 as well as its binding to viral sequences such as TAR and PBS involved in the two obligatory strand transfers of reverse transcription. Results show that Ac-HKWPWW-NH2 exhibits an almost symmetric cis-trans equilibrium at the level of the Pro residue where it is structured. The peptide binds both TAR and PBS sequences with low micromolar affinities. The cis-Pro and trans-Pro conformations of the peptide bind with comparable affinities to (-)PBS, mainly through stacking interactions between the Trp residues and the (-)PBS bases. Though all three Trp residues may contribute to the (-)PBS/Ac-HKWPWW-NH2 complex formation, Trp3 and Trp5 residues are the key residues in the complexes with the cis-Pro and trans-Pro conformations, respectively. Moreover, Ac-HKWPWW-NH2 stabilizes cTAR secondary structure and largely inhibits the NC-directed melting of cTAR. This further strengthens the interest of this peptide for deriving modified peptides capable of inhibiting NC and HIV-1 replication.
authors.affiliation: Département Pharmacologie et Physicochimie, Faculté de Pharmacie, Institut Gilbert-Laustriat, UMR 7175 CNRS/Université Louis Pasteur (Strasbourg I), 74 route du Rhin, 67401 Illkirch, France.
authors.forename: Chinappan
authors.initials: C
authors.lastname: Raja
authors.forename: Jan
authors.initials: J
authors.lastname: Ferner
authors.forename: Ursula
authors.initials: U
authors.lastname: Dietrich
authors.forename: Sergiy
authors.initials: S
authors.lastname: Avilov
authors.forename: Damien
authors.initials: D
authors.lastname: Ficheux
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Darlix
authors.forename: Hugues
authors.initials: H
authors.lastname: de Rocquigny
authors.forename: Harald
authors.initials: H
authors.lastname: Schwalbe
authors.forename: Yves
authors.initials: Y
authors.lastname: Mély
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015497:HIV-1 / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009696:Nucleic Acids / Q000737:chemistry / Q000378:metabolism; D019590:Nucleocapsid Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism*; D000099253:Trans-Activation Responsive RNA-Binding Protein
chemical_list: D018832:Molecular Chaperones; D009696:Nucleic Acids; D019590:Nucleocapsid Proteins; D009842:Oligopeptides; D016601:RNA-Binding Proteins; D014364:Tryptophan; D000099253:Trans-Activation Responsive RNA-Binding Protein