Fig. 6

TOP1-dependent repression of HIV-1 LTR promoter activity requires LTR III G4 folding and TOP1 interaction to this G4 structure. A Mutations disrupting G4 folding and TOP1 interaction reactivate HIV-1 promoter activity. The luciferase activities of HeLa LTR luciferase clones containing WT or mutated HIV-1 LTR upstream of the luciferase gene were measured and normalized for the activity of the WT clone (n = 3). B Scheme of the LTR HIV-1 promoter and GFP/Luciferase transcribed genes present in the J-Lat A1 and HeLa LTR Luciferase cell genomes. This scheme highlights the G4 region in the LTR (grey box) and the regions studied by TOP1 ChIP (Nuc0, Enhancer, Nuc1, GFP and Luc coding). C TOP1 occupancy along the HIV-1 promoter (Nuc1, Enhancer and Nuc0 regions) and transcribed gene (GFP region) present in the HIV-1 minigenome integrated in J-Lat A1 cells [63]. The occupancy was measured by ChIP assay (n = 3) performed in cells with Top1 gene previously silenced (shTop1) or control (sh-) (similar conditions as in Fig. 2). D TOP1 occupancy along the HIV-1 promoter (Nuc1, Enhancer and Nuc0 regions) and the transcribed gene (Luciferase coding region) measured by ChIP assay (n = 3) performed in HeLa LTR luciferase cells of WT, Mut1 or Mut4 LTR III sequence [62]