From the N- to the C-terminal, sacsin is reported to be composed of a ubiquitin-like domain that binds to the proteasome, three large sacsin repeats forming a “sacsin repeating region” (SRR) that may have an Hsp90-like chaperone function [5], a xeroderma pigmentosum complementation group C binding (XPCB) domain that binds to the Ube3A ubiquitin protein ligase, a DnaJ domain binding Hsc70, and a higher eukaryotes and prokaryotes nucleotide-binding (HEPN) domain mediating sacsin dimerization and binding to nucleotides or their analogs [1,5,6]. The gene discussed is SACS; the disease is xeroderma pigmentosum.