Post-transcriptional
processing
of mRNA: polyadenylation of 3' tail
[Left] The RNA
transcript is oriented 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 [PAP, PAII & III]
synthesizes a poly(A) tail and ligates it to the
free 3' of the RNA
transcript (pre-mRNA).
Note: for our purposes, appreciate that
post-transcriptional processing is done by enzyme complexes
that act on information in the RNA molecule.