Coupling of RNA polymerase II (pol II) transcription can influence processing reactions in three ways.
# localization
#* positions mRNA processing factors at the elongation complex, which raises their local concentration in the vicinity of the nascent transcript 
# kinetic coupling
#* the rate of transcript can have profound effects on RNA folding and the assembly of RNA-protein complexes
# allosteric
#* contact between the pol II elongation complex and mRNA processing factors can allosterically inhibit or activate mRNA processing factors