In UPS, the most well-known ubiquitin enzymes associated with muscle atrophy are two E3 ubiquitin-protein ligases, TRIM63 (Tripartite Motif Containing 63, or MuRF1), and FBXO32 (F-box only protein 32, or atrogin 1). The gene discussed is FBXO32; the disease is Atrophy.