COPS5 and Machado-Joseph disease: Ubiquitination is reversed by ∼100 deubiquitinase enzymes (DUBs) that are proteases consisting of five subfamilies: ubiquitin-specific proteases (USP), ubiquitin carboxyl-terminal hydrolases (UCH), ovarian tumour-like (OTUs), Machado-Joseph disease (MJD) protein domain proteases and the JAMM (JAB1/MPN/MOV34) metalloprotease family [49].