Cytoplasmic non-canonical poly(A) RNA polymerase that catalyzes the transfer of one adenosine molecule from an ATP to an mRNA poly(A) tail bearing a 3'-OH terminal group and participates in the cytoplasmic polyadenylation (PubMed:33882302). Polyadenylates mRNA encoding extracellular matrix constituents and other genes crucial for bone mineralization and during osteoblast mineralization, mainly focuses on ER-targeted mRNAs (By similarity). . This is the function of Ensembl gene identifier ENSG00000112773 (TENT5A, terminal nucleotidyltransferase 5A).