TBP and spinocerebellar ataxia type 17: TBP (TATA-binding protein), the disease protein in SCA 17, was reported to show fragmentation and fragment-dependent formation of aggregates in SCA 17 mice [18], but in vitro assays did not show a TBP substrate-specificity for caspases [22], suggesting different proteolytic enzymes to be involved in truncation of TBP.