%0 Journal Article
%T Modulation of microtubule assembly by the HIV-1 Tat protein is strongly dependent on zinc binding to Tat
%A Caroline Egel¨¦
%A Pascale Barbier
%A Pascal Didier
%A Etienne Pi¨¦mont
%A Diane Allegro
%A Olivier Chaloin
%A Sylviane Muller
%A Vincent Peyrot
%A Yves M¨¦ly
%J Retrovirology
%D 2008
%I BioMed Central
%R 10.1186/1742-4690-5-62
%X To investigate the role of zinc, we first characterized Tat apo- and holo-forms by fluorescence correlation spectroscopy and time-resolved fluorescence spectroscopy. Both of the Tat forms are monomeric and poorly folded but differ by local conformational changes in the vicinity of the cysteine-rich region. The interaction of the two Tat forms with tubulin dimers and microtubules was monitored by analytical ultracentrifugation, turbidity measurements and electron microscopy. At 20ˇăC, both of the Tat forms bind tubulin dimers, but only the holo-Tat was found to form discrete complexes. At 37ˇăC, both forms promoted the nucleation and increased the elongation rates of tubulin assembly. However, only the holo-Tat increased the amount of microtubules, decreased the tubulin critical concentration, and stabilized the microtubules. In contrast, apo-Tat induced a large amount of tubulin aggregates.Our data suggest that holo-Tat corresponds to the active form, responsible for the Tat-mediated apoptosis.Human Immunodeficiency Virus type 1 (HIV-1) infection is characterized by a massive depletion of CD4+ T cells that leads to the loss of immune competence [1,2]. This is in part mediated by the HIV-1 Tat protein, which is produced by HIV-infected cells and is efficiently taken up by the neighboring cells [3-5]. Tat is an 86 to 106-amino acid-long protein whose primary role is to transactivate the transcription of the HIV-1 proviral DNA from the long terminal repeat (LTR) by binding to the nascent TAR (Trans-Acting Responsive element) RNA sequence [6-8].In addition, extracellular Tat shows many additional functions, which contribute to the AIDS syndrome. In particular, Tat induces the apoptosis of macrophages and cytotoxic T-lymphocytes by several mechanisms [9]. These different pathways include the up-regulation of Fas ligand [10], the down-regulation of cellular genes encoding for superoxide-dismutase [11] and manganese-dependent superoxide dismutase [12], and the activation of
%U http://www.retrovirology.com/content/5/1/62