Among the eight described mammal homologs, XIAP (X-linked IAP) [2], cIAP1 (cellular IAP1), cIAP2, ML-IAP (Melanoma IAP) [3] and ILP-2 (IAP-like protein 2) [4] are enzymes of the ubiquitination reaction involved in proteostasis and the regulation of the assembly of intracellular signaling platforms. The gene discussed is XIAP; the disease is melanoma.