Polyadenylation of the 3' tail

The hnRNA product includes a signal sequence (AAUAAA) towards the 3' end. An enzyme complex cuts off the 3' end, and another enzyme complex synthesizes a poly-A tract and attaches it to the free 3' end.

[Note: The molecule shown is hnRNA, not mRNA, and is cut upstream of the signal sequence.]

Figure © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2012 by Steven M. Carr