FIGURE 6.

Run-on transcription assays. (A) The rDNA transcription unit. RNA polymerase I transcribes the 35S primary rRNA transcript, whereas RNA polymerase III transcribes the 5S rRNA in the opposite direction. PCR products corresponding to the indicated segments of the 5′ external transcribed spacer (5′ETS), the 25S rRNA, NTS, and the 5S rRNA were cloned into the pTOPO plasmid. (B) Transcription run-on analysis. The wild-type and rrp14Δ strains were cultured, permeabilized, and exposed to α-³²P-UTP for 10 min. RNA was extracted and hybridized to the plasmids slot-blotted onto Nitran membrane. Autoradiograph [B(b)] is exposed for longer than autoradiograph [B(a)].