TENT5B (terminal nucleotidyltransferase 5B) is a non-canonical poly(A) polymerase that catalyzes the addition of adenosine residues to mRNA 3' poly(A) tails in an ATP-dependent manner 1. The enzyme preferentially modifies adenosine-rich RNA substrates 1 and functions to maintain translational efficiency by preventing mRNA degradation 1. Beyond its role in mRNA polyadenylation, TENT5B exhibits tumor-suppressive functions through ubiquitination of β-catenin/CTNNB1, thereby inhibiting cell proliferation and cell cycle progression 2. In breast cancer progression, TENT5B expression is dynamically regulated through DNA methylation changes; transcriptional silencing of TENT5B promotes cell proliferation in normal breast cells, suggesting its methylation-dependent downregulation contributes to malignant progression 3. TENT5B is also identified as a potential target gene regulated by the histone methyltransferase MLL4 in non-small-cell lung cancer 4. These findings position TENT5B as a multifunctional regulator linking mRNA metabolism to cell cycle control and cancer suppression, with potential therapeutic implications in epigenome-directed cancer treatment.