Cooperative and specific binding of Vif to the 5' region of HIV-1 genomic RNA.
The viral infectivity factor (Vif) protein of human immunodeficiency virus type 1 (HIV-1) is essential for viral replication in vivo. Packaging of Vif into viral particles is mediated by an interaction with viral genomic RNA and association with viral nucleoprotein complexes. Despite recent findings on the RNA-binding properties of Vif suggesting that Vif could be involved in retroviral assembly, no RNA sequence or structure specificity has been determined so far. To gain further insight into the mechanisms by which Vif might regulate viral replication, we studied the interactions of Vif with HIV-1 genomic RNA in vitro. Using extensive biochemical analysis, we have measured the affinity of recombinant Vif proteins for synthetic RNAs corresponding to various regions of the HIV-1 genome. We found that recombinant Vif proteins bind specifically to HIV-1 viral RNA fragments corresponding to the 5'-untranslated region (5'-UTR), gag and the 5' part of pol (K(d) between 45 nM and 65 nM). RNA encompassing nucleotides 1-497 or 499-996 of the HIV-1 genomic RNA bind 9+/-2 and 21+/-3 Vif molecules, respectively, and at least some of these proteins bind in a cooperative manner (Hill constant alpha(H) = 2.3). In contrast, RNAs corresponding to other parts of the HIV-1 genome or heterologous RNAs showed poor binding capacity and weak cooperativity (K(d) > 200 nM). Moreover, RNase T1 footprinting revealed a hierarchical binding of Vif, pointing to TAR and the poly(A) stem-loop structures as primary strong affinity targets, and downstream structures as secondary sites with moderate affinity. Taken together, our findings suggest that Vif may assist other proteins to maintain a correct folding of the genomic RNA in order to facilitate its packaging and further steps such as reverse transcription. Interestingly, our results suggest also that Vif could bind the viral RNA in order to protect it from the action of the antiviral factor APOBEC-3G/3F.
Henriet
Simon
S
Unité Propre de Recherche 9002 du CNRS conventionnée à l'Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg cedex, France.
Richer
Delphine
D
Bernacchi
Serena
S
Decroly
Etienne
E
Vigne
Robert
R
Ehresmann
Bernard
B
Ehresmann
Chantal
C
Paillart
Jean-Christophe
JC
Marquet
Roland
R
D020121:5' Untranslated Regions / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D024202:Electrophoretic Mobility Shift Assay; D016346:Gene Products, vif / Q000378:metabolism*; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D054320:vif Gene Products, Human Immunodeficiency Virus
D020121:5' Untranslated Regions; D016346:Gene Products, vif; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D054320:vif Gene Products, Human Immunodeficiency Virus