of mRNA; polyadenylation of 3' tail
[Left] The hnRNA runs 5'3'
from the top left to lower right, where transcription
terminates. [Right] Upon recognition of the AAUAAA signal,
the 3' end is removed by an enzyme
complex [CFI, II] at the cut site. Another enzyme
complex [PA] synthesizes a poly(A) tail and ligates it to the free 3' of the pre-message.