Background: TBP (TATA-box-binding protein) is a key component of the multiprotein transcription factor TFIID (transcription factor IID) which binds to core promoters and activates RNA polymerase II transcription. TBP is responsible for directing TFIID binding to the TATA-box to form the pre-initiation transcriptional complex. Mutations in the polyglutamine tract of TBP are associated with the neurodegenerative disorder spinocerebellar ataxia 17.