The loss of UBQLN1 from the BJAB B-cell lymphoma led to a rapid but reversible loss of proliferative capacity, and a comprehensive quantitative proteomic analysis revealed that the major effect of UBQLN1 was to suppress the accumulation of hydrophobic mitochondrial proteins in the cytosol. The gene discussed is UBQLN1; the disease is B-cell non-Hodgkin lymphoma.