HAP1 and Machado-Joseph disease: STB/HAP1 can also interact with the causal agents of some other polyQ diseases, such as with Abelson helper integration site 1 in Joubert syndrome (Sheng et al., 2008), ataxin 3 in Machado-Joseph disease (Takeshita et al., 2011) and TATA binding protein in spinocerebellar ataxia type 17 (Prigge and Schmidt, 2007).