Figure 5. Run-on incorporation of [α-³²P]UTP into nascent RNA in nuclei isolated and incubated in polymer solution in 100 µM K-Hepes.

K⁺ was added to the medium to ∼1 mM to neutralise the nucleotide triphosphate RNA precursors. (A) nuclei isolated and incubated in 50% Ficoll; data points and error bars show means ±SEM (n = 5) for 30 min, and means and ranges (n = 2) for other points. (B) nuclei isolated and incubated in 12% 8 kDa PEG; data points and error bars show means ±SEM (n = 9 for 30 min, n = 3 for other points). Full lines show incorporation in the complete system, dashed lines with addition of α-amanitin (200 µg/ml) to inhibit RNA pol II, and dotted lines in the absence of polymer.