RTCA (RNA 3'-terminal phosphate cyclase) catalyzes the conversion of 3'-phosphate ends to 2',3'-cyclic phosphodiester ends on RNA molecules through a three-step mechanism involving ATP-dependent adenylation and nucleophilic attack by the adjacent 2'-hydroxyl group. The enzyme can also cyclize 2'-phosphate RNA ends, though at substantially lower rates 1. RTCA likely functions in cellular RNA processing and repair pathways; in bacteria, it is coregulated with the RtcB RNA ligase in an operon activated by damaged tRNAs 2. Recent evidence indicates RTCA plays a broader role in alternative splicing regulation, with large-scale evaluation identifying it among hundreds of endogenous splicing events it modulates 3. Notably, RTCA inhibits central nervous system axon regeneration following injury by regulating expression and transport of the mechanosensitive ion channel Piezo1 through the Rab10 GTPase pathway 4. Loss of RTCA promotes axon regeneration after spinal cord injury or optic nerve crush in adult mice, suggesting therapeutic potential for regenerative medicine. The gene is associated with multiple disease contexts including cancer, leukodystrophy, and neurological conditions, though specific mechanistic links in these settings require further investigation.