title: Site-selective probing of cTAR destabilization highlights the necessary plasticity of the HIV-1 nucleocapsid protein to chaperone the first strand transfer.
abstract: The HIV-1 nucleocapsid protein (NCp7) is a nucleic acid chaperone required during reverse transcription. During the first strand transfer, NCp7 is thought to destabilize cTAR, the (-)DNA copy of the TAR RNA hairpin, and subsequently direct the TAR/cTAR annealing through the zipping of their destabilized stem ends. To further characterize the destabilizing activity of NCp7, we locally probe the structure and dynamics of cTAR by steady-state and time resolved fluorescence spectroscopy. NC(11-55), a truncated NCp7 version corresponding to its zinc-finger domain, was found to bind all over the sequence and to preferentially destabilize the penultimate double-stranded segment in the lower part of the cTAR stem. This destabilization is achieved through zinc-finger-dependent binding of NC to the G(10) and G(50) residues. Sequence comparison further revealed that C•A mismatches close to the two G residues were critical for fine tuning the stability of the lower part of the cTAR stem and conferring to G(10) and G(50) the appropriate mobility and accessibility for specific recognition by NC. Our data also highlight the necessary plasticity of NCp7 to adapt to the sequence and structure variability of cTAR to chaperone its annealing with TAR through a specific pathway.
authors.affiliation: Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, UMR 7213 CNRS, Université de Strasbourg, 67401 Illkirch, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Godet
authors.forename: Cyril
authors.initials: C
authors.lastname: Kenfack
authors.forename: Frédéric
authors.initials: F
authors.lastname: Przybilla
authors.forename: Ludovic
authors.initials: L
authors.lastname: Richert
authors.forename: Guy
authors.initials: G
authors.lastname: Duportail
authors.forename: Yves
authors.initials: Y
authors.lastname: Mély
mesh_terms: D015075:2-Aminopurine / Q000737:chemistry; D001483:Base Sequence; D017124:Conserved Sequence; D004279:DNA, Viral / Q000737:chemistry; D016325:HIV Long Terminal Repeat; D009154:Mutation; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D013050:Spectrometry, Fluorescence; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; C071884:NCP7 protein, Human immunodeficiency virus 1; D054301:gag Gene Products, Human Immunodeficiency Virus; D015075:2-Aminopurine