Capping, splicing, and 3' processing are independently stimulated by RNA polymerase II: different functions for different segments of the CTD.
Fong N, Bentley DL. Capping, splicing, and 3' processing are independently stimulated by RNA polymerase II: different functions for different segments of the CTD. Genes Dev. 2001 Jul 15; 15(14):1783-95.