U6 snRNA-specific terminal uridylyltransferase 1; speckle targeted PIP5K1A-regulated poly(A) polymerase; Star-PAP; RNA-binding motif protein 21; RNA-binding protein 21; U6-TUTase (TUT1, RBM21)

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Function

poly(A) polymerase that creates the 3'-poly(A) tail of specific pre-mRNAs
localizes to nuclear speckles together with PIP5K1A & mediates polyadenylation of a selected mRNAs, including HMOX1
in addition to polyadenylation, also required for the 3'-end cleavage of pre-mRNAs
- binds to the 3'UTR of targeted pre-mRNAs
- promotes recruitment & assembly of the CPSF complex on the 3'UTR of pre-mRNAs
in addition to adenylyltransferase activity, also has uridylyltransferase activity
- since the ATP ratio is higher than UTP in cells, it likely functions primarily as a poly(A) polymerase
- acts as a specific terminal uridylyltransferase for U6 snRNA in vitro
  - responsible for a controlled elongation reaction that results in restoration of the four 3'-terminal UMP- residues found in newly transcribed U6 snRNA
not involved in replication-dependent histone mRNA degradation
phosphorylated by CK1 in the proline-rich (Pro-rich) region
phosphorylated upon DNA damage, probably by ATM or ATR
associates with the CPSF complex
- interacts with CPSF1 & CPSF3
interacts with PIP5K1A

UTP + RNA(n) = diphosphate + RNA(n+1)

ATP + RNA(n) = diphosphate + RNA(n+1)

widely expressed