Figure 6.

Possible steps leading to the elimination of a DSR-containing mRNA. Step 1, Mmi1p bound to the DSR sequence interacts with a conventional polyadenylation complex and promotes a polyadenylation reaction of a somewhat unusual nature. Step 2, the poly(A)-binding protein Pab2p is recruited to the produced poly (A) tail. The affinity of Mmi1p for Pab2p is likely to facilitate this recruitment. Step 3, Pab2p, probably in collaboration with Mmi1p, recruits a nuclear exosome to the target transcript, which then digests it from the 3’ end. Reproduced from Ref. 76.