Hexim and 7SK are not recruited at the HIV-1 transcription site. U2OS_HIV-1 cells were transfected with vectors expressing Tat alone (upper panel), or Tat and MS2-GFP (middle and lower panels). 24h later, cells were fixed and processed. Upper panel: cells were hybridized in situ with fluorescent oligonucleotide probes detecting 7SK (red) or the MS2 repeat (green). Middle and lower panels, cells were labeled with antibodies against Hexim1 (red, middle panel), or cyclin T1 (red, lower panel).