Cytoplasmic uridylyltransferase that mediates the terminal uridylation of mRNAs with short poly(A) tails such as such as act1, hcn1 and urg1 mRNAs, hence facilitating global mRNA decay (PubMed:17353264, PubMed:17449726, PubMed:19430462, PubMed:22751018, PubMed:22885303). Uridylates the 3' ends of actin mRNAs upon S-phase arrest (PubMed:17353264). Has also a weak poly(A) polymerase (PAP) activity (PubMed:22751018, PubMed:22885303). Residue His-336 is responsible for the specificity for UTP (PubMed:22751018, PubMed:22885303). Involved in cell cycle arrest where in association with crb2/rhp9 and chk1 it inhibits unscheduled mitosis (PubMed:10757807). RNA(n) + UTP = diphosphate + RNA(n)-3'-uridine ribonucleotide ATP + RNA(n) = diphosphate + RNA(n)-3'-adenine ribonucleotide Mutation of His-336 to Asn decreases the Km for ATP to 65 uM and increases the Km for UTP to 45 uM. Stabilizes urg1 transcripts (PubMed:19430462). Belongs to the DNA polymerase type-B-like family. Has been first identified as a cytoplasmic poly(A) polymerase (PAP) implicated in cell cycle checkpoint controls (PubMed:12218190). Further studies showed that cid1 had robust poly(U) polymerase activity in vitro and that is was rather an RNA uridylyltransferase (PubMed:17353264, PubMed:17449726).