The C-terminal region of TENT5 Proteins Drives ER-associated mRNA Polyadenylation via FNDC3 interaction [RNA-seq]

Spatial regulation of mRNA polyadenylation is a key emerging mechanism shaping cellular function. The TENT5/FAM46 family comprises four non-canonical poly(A) polymerases that stabilize transcripts encoding ER-targeted proteins, with mutations linked to diseases of professional secretory cells. Using transcriptomic profiling coupled with systematic mutagenesis, we uncover how paralog-specific evolutionary divergence dictates distinct subcellular localization, interaction, and functional outcomes. TENT5D, the most ER-associated member, triggers widespread proteome remodeling, boosting the concerted expression of ER, ERGIC, Golgi, and lysosomal proteins. In contrast, TENT5B lacks ER targeting and regulates proteins involved in cell division. Mechanistically, a member-specific C-terminal region that binds ER-transmembrane FNDC3 proteins is necessary and sufficient for ER localization. Altogether, our findings reveal a domain-encoded mechanism linking TENT5 localization to transcript selectivity and secretory output. The TENT5–FNDC3 axis thus emerges as a key orchestrator of the cellular translatome and organelle identity.