Schematic overview of rRNA transcription and processing in T. brucei. The top part represents a rRNA gene repeat, showing the position of the genes encoding the eight rRNA species. The four domains (I to IV) that comprise the promoter region are indicated. The arrow represents the transcription start site. Please note that the scales are different upstream and downstream of the transcription start site. After transcription by Pol I, a primary transcript is generated (9.6 kb). The location of 5′- and 3′-UTRs and ITSs (1 to 7) is shown. Processing of the primary transcript produces the eight mature rRNA species, which are part of the SSU (18S) or the LSU (5.8S, 24Sα, sr1, 24Sβ, sr2, sr4, and sr6). The positions of the main cleavage sites are denoted with small vertical arrows.