Parkin ubiquitinates itself predominantly via K27- and K29-linked chains which may protect it from autophagic degradation, and preferential cleavage of these chains by polyQ-expanded ataxin-3 can result in enhanced autophagic degradation of parkin, as reflected by a profound reduction in parkin levels in MJD mice [89]. Here, PRKN is linked to Spinocerebellar ataxia type 3.