Speckle targeted PIP5K1A-regulated poly(A) polymerase (TUT1)

Poly(A) polymerase that creates the 3'-poly(A) tail of particular pre-mRNAs. In addition to polyadenylation, it's also necessary for the 3'-end cleavage of pre-mRNAs: binds to the 3'UTR of targeted pre-mRNAs and promotes the recruitment and assembly of the CPSF complex on the 3'UTR of pre-mRNAs.

In addition to adenylyltransferase activity, also has uridylyltransferase activity. However, the ATP ratio is higher than UTP in cells, suggesting that it functions primarily as a poly(A) polymerase.