title: An anti-apoptotic protein, Hax-1, inhibits the HIV-1 rev function by altering its sub-cellular localization.
abstract: The human immunodeficiency virus type 1 (HIV-1) Rev protein facilitates the nuclear export of viral mRNA containing the Rev response element (RRE). Although several host proteins co-operating with Rev in viral RNA export have been reported, little is known about the innate host defense factors that Rev overcomes to mediate the nuclear export of unspliced viral mRNAs. We report here that an anti-apoptotic protein, HS1-associated protein X-1 (Hax-1), a target of HIV-1 Vpr, interacts with Rev and inhibits its activity in RRE-mediated gene expression. Co-expression of Sam68 emancipates Rev activity from Hax-1-mediated inhibition. Hax-1 does not bind to RRE RNA by itself, but inhibits Rev from binding to RRE RNA in vitro. The impact of Hax-1 on Rev/RRE interactions in vitro correlates well with the reduced level of RRE-containing mRNA in vivo. Immunofluorescence studies further reveal that Hax-1 and Rev are cytoplasmic and nuclear proteins, respectively, when expressed independently. However, in Hax-1 co-expressing cells, Rev is translocated from the nucleus to the cytoplasm, where it is co-localized with Hax-1 in the cytoplasm. We propose that over-expression of Hax-1, possibly through binding to Rev, may interfere with the stability/export of RRE-containing mRNA and target the RNA for degradation.
authors.affiliation: Department of Immunology and Microbiology, Wayne State University-School of Medicine, Detroit, Michigan 48201, USA.
authors.forename: Suhasini
authors.initials: S
authors.lastname: Modem
authors.forename: Thipparthi R
authors.initials: TR
authors.lastname: Reddy
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015694:Gene Products, rev; D005982:Glutathione Transferase / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D009154:Mutation; D010957:Plasmids; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D020218:Response Elements; D013347:Subcellular Fractions / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism; D014162:Transfection; D054321:rev Gene Products, Human Immunodeficiency Virus / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D015694:Gene Products, rev; C104759:HAX1 protein, human; C489559:KHDRBS1 protein, human; D011506:Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D054321:rev Gene Products, Human Immunodeficiency Virus; C514860:rev protein, Human Immunodeficiency Virus-1; D015500:Chloramphenicol O-Acetyltransferase; D005982:Glutathione Transferase