Fig. 4. H2AZ does not colocalize with sites of transcription. (A) Nascent RNA transcripts from bloodstream-form cells were labeled with BrUTP and examined by indirect immunofluorescence. H2AZ (red) and BrUTP (green) occupy distinct sites within the nucleus. (B) In the presence of 100 µg/ml -amanitin, incorporation of BrUTP (green) is limited to sites of RNA polymerase I transcription, which do not overlap with H2AZ (red). For both A and B, DNA (blue) was detected with DAPI. Bar, 2 µm. BrUTP incorporation into the kinetoplasts is detected in the presence and, less obviously, in the absence of -amanitin, probably reflecting the massive uridine incorporation that occurs during RNA editing, including in the bloodstream form (Schnaufer et al., 2001).