Translin (also known as TB-RBP), and its binding partner protein TRAX (translin-associated factor-X) are a paralogous pair of conserved proteins, and oligomeric complexes of TRAX and translin are known as C3PO proteins (for component 3 promoter of RNA-induced silencing complex or RISC). The Translin-Trax complex enhances the removal of the passenger strand in RNAi and the formation of active RISC. Translin and Trax participate in a variety of nucleic acid metabolism pathways in addition to RNAi and have been implicated in a wide range of biological activities, including mRNA processing, cell growth regulation, spermatogenesis, neuronal development/function, genome stability regulation and carcinogenesis; however, their precise role in some of the processes remains unclear. It has been shown that Trax subunit, but not Translin, possesses a Glu-Glu-Asp catalytic center with the capacity to digest RNA as well as DNA; this catalytic activity is required for passenger-strand removal and RISC activation in RNAi. In Archaeoglobus fulgidus, Trax-like-subunits assemble into an octameric structure, highly similar to human C3PO; its complex with duplex RNA reveals that the octamer entirely encapsulates a single 13-base-pair RNA duplex inside a large inner cavity.
Jiyao W et al.(2023). "The conserved domain database in 2023.",