Sequential Inverse Dysregulation of the RNA Helicases DDX3X and DDX3Y Facilitates MYC-Driven Lymphomagenesis

DDX3X is a ubiquitously expressed RNA helicase involved in multiple stages of RNA biogenesis. DDX3X is frequently mutated in Burkitt lymphoma but the functional basis for this is unknown. Here, we show that loss-of-function DDX3X mutations are also commonly found in MYC-translocated diffuse large B cell lymphoma and reveal functional co-operation between mutant DDX3X and MYC. DDX3X promotes translation of mRNAs encoding components of the core translational machinery, thereby driving global protein synthesis. Loss-of-function DDX3X mutations moderate MYC-driven global protein synthesis, thereby buffering MYC-induced proteotoxic stress during early lymphomagenesis. Established lymphoma cells subsequently restore full protein synthetic capacity by aberrant expression of DDX3Y, a Y-chromosome homologue that is normally expressed exclusively in testis.  These findings show that DDX3X loss-of-function can buffer MYC-driven proteotoxic stress, and highlight the capacity of male B cell lymphomas to later compensate for this loss by ectopic DDX3Y expression.