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. 2009 Jun 1;23(11):1247–1269. doi: 10.1101/gad.1792809

Figure 3.

Figure 3.

Organization of the rDNA genes in yeast and mouse. The rDNA transcription unit is 9.1-kb long in yeast and 43-kb long in human. It consists of a 35S precursor in yeast and 45S in human. The precursor contains the sequences of the mature 18S, 5.8S, and 25S/28S rRNAs separated by two ITSs, ITS1 and ITS2, and is flanked by two ETSs, the 5′ETS and 3′ETS. In yeast, the IGS is interrupted by the 5S rDNA gene, which is transcribed by RNAPIII in the opposite orientation. In yeast, RNAPI terminates predominantly at the T1 terminator, apparently dependent on Reb1 and located ∼90 bp downstream from the 25S sequence, in IGS1 (IGS upstream of the 5S gene). The “fail-safe” terminator (T2) is located ∼250 bp downstream from the 25S sequence. The RFB that binds Fob1 is located downstream from T2. In mouse, the major terminator (Sal box 1) is located ∼550 nt downstream from the 28S RNA. The origin of bidirectional replication (OBR) in mouse and the autonomously replicating sequence (ARS) in yeast are indicated, as well as the Rnt1 cleavage and the T0 terminator.