Figure 1. Nucleosome-induced transcription arrest. The nucleosome is viewed from top. Only one superhelical turn of the DNA around a histone octamer (green circle) is shown. The RNA in the elongation complex is shown as a red arrow. RNA polymerase in the active elongation complex is shown in blue; in the paused or arrested elongation complex, it is shown in pink. Pol II, RNA polymerase II; TFIIS, transcription factor S-II.