CASP3 and spinocerebellar ataxia 7: At the molecular level, aggregates of mutant ataxin-7 sequester ubiquitin proteasome subunit 20S, chaperones Hsp70 and Hsp40, caspase-3, transcription factor CREB-binding protein (CBP) and p53, as shown in cellular and mouse models of SCA7, and in brain and retina postmortem tissues derived from SCA7 patients [17,18,19].