Two novel Ub-protein ligases, atrogin-1 (muscle atrophy F-box protein) and muscle ring-finger protein (MuRF-1), are consistently up-regulated in murine models of muscle atrophy, and are thought to ubiquitinate both regulatory (e.g. calcineurin and MyoD) and structural (e.g. myosin and troponin I) proteins, thus directing the specific degradation of proteins during muscle atrophy [1], [12], [13], [15]–[21]. The gene discussed is TRIM63; the disease is muscle atrophy.