Connecting transcription to messenger RNA processing.

The production of messenger RNA by gene transcription requires at least three RNA-processing mechanisms: capping, splicing and polyadenylation. All three reactions occur in intimate association with the elongating polymerase complex through the C terminus of the largest subunit of RNA polymerase II. The processing of mRNA is therefore orchestrated to act on the nascent RNA as soon as it emerges from the polymerase complex.