Highly stable oligomerization forms of HIV-1 Tat detected by monoclonal antibodies and requirement of monomeric forms for the transactivating function on the HIV-1 LTR

Tosi, Giovanna; Meazza, Raffaella; Barbaro, Andrea De Lerma; D’Agostino, Antonella; Mazza, Stefania; Corradin, Giampietro; Albini, Adriana; Noonan, Douglas M.; Ferrini, Silvano; Accolla, Roberto S.

doi:10.1002/(sici)1521-4141(200004)30:4<1120::aid-immu1120>3.0.co;2-4

Cited by 29 publications

(18 citation statements)

References 18 publications

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“…Based on this, we suggest that the faster-migrating protein corresponds to the monomeric form of CotC, whereas the slower one results from the assembly of CotC monomers into a homodimer. Cases of dimers and also oligomers resistant to detergent treatment and strong reducing conditions have been reported previously and are rather frequent (25,28,29). CotC-CotC interaction in a yeast two-hybrid system.…”

Section: Vol 186 2004supporting

confidence: 53%

Assembly of Multiple CotC Forms into the Bacillus subtilis Spore Coat

et al. 2004

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We report evidence that the CotC polypeptide, a previously identified component of the Bacillus subtilis spore coat, is assembled into at least four distinct forms. Two of these, having molecular masses of 12 and 21 kDa, appeared 8 h after the onset of sporulation and were probably assembled on the forming spore immediately after their synthesis, since no accumulation of either of them was detected in the mother cell compartment, where their synthesis occurs. The other two components, 12.5 and 30 kDa, were generated 2 h later and were probably the products of posttranslational modifications of the two early forms occurring directly on the coat surface during spore maturation. None of the CotC forms was found either on the spore coat or in the mother cell compartment of a cotH mutant. This indicates that CotH serves a dual role of stabilizing the early forms of CotC and promoting the assembly of both early and late forms on the spore surface.The Bacillus subtilis spore is encased within a complex multilayered protein structure known as the coat, whose role is to protect the spore against bactericidal enzymes and chemicals, such as lysozyme and chloroform, and to influence the spore's ability to germinate in response to appropriate germinants. However, the recent finding that a component of the B. subtilis coat has laccase activity (20) suggests that the coat may have other, so far unexplored, roles. The coat is composed of a heterogeneous group of over 25 polypeptides arranged into three main structural layers: a diffuse undercoat, a laminated lightly staining inner layer, and a thick electron-dense outer coat. Several of these polypeptides have been studied, and their structural genes (cot genes) have been identified. Expression of all cot genes is governed by a cascade of four transcription factors, acting specifically in the mother cell compartment of the sporangium in the sequence sigma E-SpoIIID-sigma K-GerE, with sigma E and sigma K being RNA polymerase sigma factors and SpoIIID and GerE being DNA-binding proteins acting in conjunction with sigma E-and sigma K-driven RNA polymerase (5, 11).

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Section: Vol 186 2004supporting

confidence: 53%

Assembly of Multiple CotC Forms into the Bacillus subtilis Spore Coat

et al. 2004

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“…Previous reports stated that antibodies directed to the Tat N-terminal domain or to the basic region could equally inhibit exogenous Tat-induced transactivation by preventing Tat uptake by the cell (29,30). The limited ability of B1E3 and J3B2 to neutralize transactivation in this assay could be linked to their poor reactivity to rTat, as observed in Western blotting, immunoprecipitation, or Biacore experiments, while scFvs seem to bind strongly to the rTat N-terminal epitope under these experimental conditions.…”

mentioning

confidence: 72%

Generation and Characterization of Neutralizing Human Monoclonal Antibodies against Human Immunodeficiency Virus Type 1 Tat Antigen

Moreau

Hoebeke

Zagury

et al. 2004

J Virol

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The human immunodeficiency virus Tat regulatory protein is essential for virus replication and pathogenesis. From human peripheral blood mononuclear cells of three Tat toxoid-immunized volunteers, we isolated five Tat-specific human monoclonal antibodies (HMAbs): two full-length immunoglobulin G (IgG) antibodies and three single-chain fragment-variable (scFv) antibodies. The two IgGs were mapped to distinct epitopes within the basic region of Tat, and the three scFvs were mapped to the N-terminal domain of Tat. The three scFvs were highly reactive with recombinant Tat in Western blotting or immunoprecipitation, but results were in contrast to those for the two IgGs, which are sensitive to a particular folding of the protein. In transactivation assays, scFvs were able to inhibit both active recombinant Tat and native Tat secreted by a transfected CEM cell line while IgGs neutralized only native Tat. These HMAbs were able to reduce viral p24 production in human immunodeficiency virus type 1 strain IIIB chronically infected cell lines in a dose-dependent manner.

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“…The mAb 7B11 (IgG2a), which blocks CCR3, was provided by Leukosite (Boston, MA); the mAbs against HIV-1 Tat protein (6.3G12 and 6.15F4) were produced by immunizing BALB/c mice with synthetic 1-86 Tat protein, and characterizing them for their epitope specificity as recently described (45). Ab 6.3G12 recognizes a conformational epitope of 1-86 Tat protein, whereas Ab 6.15F4 recognizes the epitope RRQR (45) of the Tat basic region domain.…”

Section: Reagentsmentioning

confidence: 99%

“…A mouse monoclonal IgG anti-␣ chain of the high affinity receptor for IgE (anti-Fc⑀RI) was donated by Dr. John Hakimi (Hoffmann-LaRoche, Nutley, NJ). The HIV-1 Tat protein used in these experiments was obtained by solid phase synthesis using the F-moc/dextran-coated charcoal/HOBL strategy (45). HIV-1 Tat was dissolved at 10 g/ml in PBS buffer containing 0.1 mM DTT and was frozen in aliquots at Ϫ80°C.…”

Section: Reagentsmentioning

confidence: 99%

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Tat Protein Is an HIV-1-Encoded β-Chemokine Homolog That Promotes Migration and Up-Regulates CCR3 Expression on Human FcεRI+ Cells

Paulis

Palma

Gioia

et al. 2000

The Journal of Immunology

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Human basophils and mast cells express the chemokine receptor CCR3, which binds the chemokines eotaxin and RANTES. HIV-1 Tat protein is a potent chemoattractant for basophils and lung mast cells obtained from healthy individuals seronegative for Abs to HIV-1 and HIV-2. Tat protein induced a rapid and transient Ca2+ influx in basophils and mast cells, analogous to β-chemokines. Tat protein neither induced histamine release from human basophils and mast cells nor increased IL-3-stimulated histamine secretion from basophils. The chemotactic activity of Tat protein was blocked by preincubation of FcεRI+ cells with anti-CCR3 Ab. Preincubation of Tat with a mAb anti-Tat (aa 1–86) blocked the migration induced by Tat. In contrast, a mAb specific for the basic region (aa 46–60) did not inhibit the chemotactic effect of Tat protein. Tat protein or eotaxin desensitized basophils to a subsequent challenge with the autologous or the heterologous stimulus. Preincubation of basophils with Tat protein up-regulated the level of CCR3 mRNA and the surface expression of the CCR3 receptor. Tat protein is the first identified HIV-1-encoded β-chemokine homologue that influences the directional migration of human FcεRI+ cells and the expression of surface receptor CCR3 on these cells.

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Highly stable oligomerization forms of HIV-1 Tat detected by monoclonal antibodies and requirement of monomeric forms for the transactivating function on the HIV-1 LTR

Cited by 29 publications

References 18 publications

Assembly of Multiple CotC Forms into the Bacillus subtilis Spore Coat

Assembly of Multiple CotC Forms into the Bacillus subtilis Spore Coat

Generation and Characterization of Neutralizing Human Monoclonal Antibodies against Human Immunodeficiency Virus Type 1 Tat Antigen

Tat Protein Is an HIV-1-Encoded β-Chemokine Homolog That Promotes Migration and Up-Regulates CCR3 Expression on Human FcεRI+ Cells

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