TRBP (transactivation response RNA binding protein) is a protein that increases HIV-1 expression and replication by inhibition of the interferoninduced protein kinase PKR. TRBP overexpression is associated with reduced abundance of phosphorylated PKR and stimulation of protein translation. TRBP has a physiological role in spermatogenesis and growth control during development. It is oncogenic upon overexpression, likely because of its association with PKR, with the PKR activator PACT, and with the tumor suppressor Merlin. TRBP was identified as a merlin interacting protein by Gal4-based yeast two-hybrid screening of a human adult brain cDNA library. Merlin can inhibit tumorigenesis mediated by TRBP and can regulate the protein translation pathways controlled by TRBP. Dicer is a key enzyme involved in RNA interference (RNAi) and microRNA (miRNA) pathways. Ago-2, a member of the Argonaute family, Dicer and TRBP comprise the catalytic core of the RNA induced silencing complex (RISC).