Fig. 4.

Residues 253-285 of CIITA are essential but not sufficient to inhibit Tat-mediated HIV-1 LTR transactivation. a 293T cells were co-transfected with fixed amounts of pHIV-1LTR Luc, phRL-CMV, pTat and increasing amounts of flag-tagged CIITA full-length or the deletion mutants listed below the western blot analyses. The results of a representative experiment are shown. Mean luciferase activities, normalized to Renilla activity, are presented as percentages relative to activation by Tat set to 100 % (black column 2). Column 1 represents the basal activity of cells transfected with the pcDNA3 vector. The expression of recombinant fCIITA proteins in cell extracts was evaluated by anti-flag western blotting. b Schematic representation of the results of the gene reported assay illustrated in panel a. CIITA proteins used for the mapping are shown, along with their capacity to inhibit Tat-dependent activation of LTR promoter (+). The endpoints of CIITA full-length and CIITA deletion mutants are indicated. At the top is a diagram of CIITA with its domains, labeled as follows: AD activation domain, P/S/T proline/serine/threonine-rich domain, GBD GTP-binding domain, and LRR leucine-rich repeats