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. Author manuscript; available in PMC: 2017 Apr 7.
Published in final edited form as: Cell. 2016 Mar 24;165(2):372–381. doi: 10.1016/j.cell.2016.02.045

Figure 6. The onset of splicing coincides with intron exit from Pol II.

Figure 6

(A) Splicing catalysis starts when WT and Fast Pol II reach ~26 and 27 nt downstream of 3’SSs (green), respectively. Splicing saturation is reached within ~130 and 353 nt (blue), respectively. The spliceosome and mutant Pol II are separated by a longer stretch of nascent RNA at splicing completion.

(B) Schematic diagram showing that 15 nt of nascent RNA is protected by Pol II, and 9 nt is bound by the spliceosome (grey shades). At splicing onset 26–27 nt downstream of 3’SSs, the spliceosome and Pol II are separated by only 2–3 nt nascent RNA. Introns (red) and exons (black) are depicted.