FIG. 4.

Transcription in the absence and presence of an archaeal nucleosome. Ternary complexes containing a ³²P-labeled 24-nt U-less transcript incubated with HMtA2 (+HMtA2) or without HMtA2 (−HMtA2) were added to a complete reaction mixture and placed at 58°C. Aliquots were taken at the times indicated (seconds), and the transcripts synthesized were separated by electrophoresis and visualized by phosphorimaging. Control lanes contained nucleotide size standards (S1 and S2). In the diagrams, the template DNA is shown to scale, with or without the positioned archaeal nucleosome. Footprinting studies indicate that an archaeal RNAP in a ternary complex extends ∼12 bp downstream from the site of nucleoside triphosphate polymerization (52). The rate of transcription was estimated, as indicated, from the increase in length of transcripts during a 2-s incubation at 58°C.