COPS5 and Machado-Joseph disease: DUBs can be classified into six families: ubiquitin C-terminal hydrolase (UCH), ubiquitin-specific protease (USP), ovarian tumor (OTU), Machado-Joseph disease (MJD), motif interacting with Ub-containing novel DUB (MINDY), and JAB1/MPN/Mov34 metalloenzyme (JAMM) families [19–21].