Analysis of NCp7-dependent activation of HIV-1 cDNA integration and its conservation among retroviral nucleocapsid proteins.
HIV-1 nucleocapsid protein NCp7 is a small basic protein with two zinc fingers, found in the virion core where several hundred molecules coat the genomic RNA. NCp7 has nucleic acid chaperone properties that guide reverse transcriptase (RT) to synthesize the proviral DNA flanked by the long terminal repeats (LTR). In vitro, NCp7 can strongly activate magnesium-dependent LTR-DNA strand transfer by integrase (IN). Here we show that IN activation relies on both the basic residues and the zinc fingers of NCp7. NCp7 lacking the zinc fingers binds DNA but moderately stimulates strand transfer by IN. The NCp7 zinc-finger domain binds DNA poorly and does not efficiently stimulate IN activity. However, the NC zinc-finger domain can complement DNA binding to restore full activation of strand transfer by IN. We propose that the basic residues and the zinc fingers function together to stabilize IN at the LTR ends and promote the formation of a nucleoprotein complex competent for integration. We also show that these properties of HIV-1 NCp7 are remarkably conserved among nucleocapsid proteins of retrotransposon and retrovirus origins.
Poljak
Leonora
L
Laboratoire de Biologie Moléculaire Eucaryote, CNRS UMR 5099, IFR 109, 118 route de Narbonne, 31062 Toulouse Cedex 4, France.
Batson
Susan M
SM
Ficheux
Damien
D
Roques
Bernard P
BP
Darlix
Jean-Luc
JL
Käs
Emmanuel
E
D000595:Amino Acid Sequence; D000818:Animals; D002213:Capsid / Q000737:chemistry* / Q000378:metabolism*; D036022:Capsid Proteins; D017124:Conserved Sequence; D004279:DNA, Viral / Q000235:genetics*; D019143:Evolution, Molecular; D015683:Gene Products, gag / Q000737:chemistry* / Q000378:metabolism*; D019427:HIV Integrase / Q000378:metabolism; D016325:HIV Long Terminal Repeat / Q000235:genetics; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins; D016662:Virus Integration; D016335:Zinc Fingers; D054301:gag Gene Products, Human Immunodeficiency Virus
D036022:Capsid Proteins; D004279:DNA, Viral; D015683:Gene Products, gag; C071884:NCP7 protein, Human immunodeficiency virus 1; D014764:Viral Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus; D019427:HIV Integrase