UBB and juvenile Huntington disease: Although UBB+1 is successfully degraded under normal conditions when its levels are very low in the cells (Lindsten et al., 2002), it tends to accumulate specifically in affected cells in several neurodegenerative diseases characterized by the presence of misfolded proteins, such as Alzheimer’s disease (AD) and Huntington’s disease (van Leeuwen et al., 1998b; de Pril et al., 2004), as well as in some non-neuronal pathologies such as liver pathologies (French et al., 2001; Wu et al., 2002) and sporadic inclusion body myositis muscle fibers (Fratta et al., 2004).