Cytoplasmic poly(A) RNA polymerase that adds successive AMP monomers to the 3'-end of specific RNAs, forming a poly(A) tail. In contrast to the canonical nuclear poly(A) RNA polymerase, it only adds poly(A) to selected cytoplasmic mRNAs (PubMed:15070731). Does not play a role in replication-dependent histone mRNA degradation (PubMed:18172165). Adds a single nucleotide to the 3' end of specific miRNAs, monoadenylation stabilizes and prolongs the activity of some but not all miRNAs (PubMed:23200856). ATP + RNA(n) = diphosphate + RNA(n)-3'-adenine ribonucleotide Interacts with CPEB1, CPEB2, CPSF1 and PABPC1. Expressed in brain. Within brain, it is expressed in cerebellum, hippocampus and medulla. Belongs to the DNA polymerase type-B-like family. GLD2 subfamily.