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. Does not play a role in replication-dependent histone mRNA degradation (By similarity). ATP + RNA(n) = diphosphate + RNA(n)-3'-adenine ribonucleotide Interacts with CPEB1, CPEB2, CPSF1 and PABPC1. Ubiquitous. In brain, it is highly expressed in the cerebral cortex, cerebellum, hippocampus and olfactory bulb. Expressed in oocytes from metaphase I to metaphase II during oocyte maturation. Mice are normal and healthy. Poly-A tail elongation in oocytes is not affected and mice are fertile. Belongs to the DNA polymerase type-B-like family. GLD2 subfamily.