HIV-1 Vif binds to APOBEC3G mRNA and inhibits its translation.
The HIV-1 viral infectivity factor (Vif) allows productive infection of non-permissive cells (including most natural HIV-1 targets) by counteracting the cellular cytosine deaminases APOBEC-3G (hA3G) and hA3F. The Vif-induced degradation of these restriction factors by the proteasome has been extensively studied, but little is known about the translational repression of hA3G and hA3F by Vif, which has also been proposed to participate in Vif function. Here, we studied Vif binding to hA3G mRNA and its role in translational repression. Filter binding assays and fluorescence titration curves revealed that Vif tightly binds to hA3G mRNA. Vif overall binding affinity was higher for the 3'UTR than for the 5'UTR, even though this region contained at least one high affinity Vif binding site (apparent K(d) = 27 +/- 6 nM). Several Vif binding sites were identified in 5' and 3'UTRs using RNase footprinting. In vitro translation evidenced that Vif inhibited hA3G translation by two mechanisms: a main time-independent process requiring the 5'UTR and an additional time-dependent, UTR-independent process. Results using a Vif protein mutated in the multimerization domain suggested that the molecular mechanism of translational control is more complicated than a simple physical blockage of scanning ribosomes.
Mercenne
Gaëlle
G
Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 15 rue René Descartes, 67084, Strasbourg cedex, France.
Bernacchi
Serena
S
Richer
Delphine
D
Bec
Guillaume
G
Henriet
Simon
S
Paillart
Jean-Christophe
JC
Marquet
Roland
R
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000071480:APOBEC-3G Deaminase; D001665:Binding Sites; D003564:Cytidine Deaminase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009154:Mutation; D014176:Protein Biosynthesis; D023302:Protein Footprinting; D012333:RNA, Messenger / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D012333:RNA, Messenger; D054320:vif Gene Products, Human Immunodeficiency Virus; C514847:vif protein, Human immunodeficiency virus 1; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase