Based on the identification of TRIM25 as an ERG-binding protein and on the observation that TRIM25 knockdown causes an increase in ERG protein levels in VCaP cells, we hypothesized that TRIM25 functions as an ERG ubiquitin ligase, which initiates a pathway leading to ERG degradation in fusion-positive prostate cancer. The gene discussed is TRIM25; the disease is Familial prostate cancer.