The function of TENT5C (terminal nucleotidyltransferase 5C, Ensembl gene identifier ENSG00000183508) is as follows. Catalyzes the transfer of one adenosine molecule from an ATP to an mRNA poly(A) tail bearing a 3'-OH terminal group and enhances mRNA stability and gene expression (PubMed:28931820, PubMed:32009146, PubMed:34048638). Can also elongate RNA oligos ending with uridine molecule, provided that the sequence is adenosine-rich (PubMed:34048638). Mainly targets mRNAs encoding endoplasmic reticulum- targeted protein (PubMed:28931820). {ECO:0000269|PubMed:28931820, ECO:0000269|PubMed:32009146, ECO:0000269|PubMed:34048638}. (Microbial infection) Seems to enhance replication of some viruses, including yellow fever virus, in response to type I interferon. .