In eukaryotes, almost all RNA molecules are processed at their 3’ ends and most mRNAs are polyadenylated in the nucleus by canonical poly(A) polymerases (PAPs). Recently, several new non-canonical poly(A) (ncPAPs) and poly(U) polymerases (PUPs) have been discovered that have more specific regulatory roles. In contrast to canonical ones, their functions are more diverse; some induce RNA decay while ...