Prolyl 3,4-dihydroxylase that catalyzes 3,4-dihydroxylation of 'Pro-64' of small ribosomal subunit uS12 (RPS23A and RPS23B), thereby regulating protein translation termination efficiency. Part of a messenger ribonucleoprotein (mRNP) complex at the 3'-UTR of mRNAs. It associates specifically with components of the translation termination complex and is involved in both translation termination and in regulation of normal mRNA decay through translation termination-coupled poly(A) shortening. 2-oxoglutarate + [ribosomal protein uS12]-L-proline + O2 = [ribosomal protein uS12]-(3S)-3-hydroxy-L-proline + CO2 + succinate 2-oxoglutarate + [ribosomal protein uS12]-(3S)-3-hydroxy-L-proline + O2 = [ribosomal protein uS12]-(3S)-3,4-dihydroxy-L-proline + CO2 + succinate Binds 1 Fe(2+) ion per subunit. Monomer and homodimer (PubMed:20630870, PubMed:20040577). Interacts with FRK1, eRF1 (SUP1), eRF3 (SUP35) and polyadenylate-binding protein PAB1. Interacts with ETT1 (PubMed:16809762, PubMed:20489023). Decrease of translation termination efficacy and an increase in mRNAs half-lives and longer mRNA poly(A) tails. Present with 8910 molecules/cell in log phase SD medium. Belongs to the TPA1 family.