Interaction Analysis Between Polyglutamine-expanded TATA Box Binding Protein (TBP) and High Mobility Group Box 1 (HMGB1)

Abstract

Spinocerebellar ataxia type 17 (SCA17) involves the expression of a polyglutamine-expanded TATA box binding protein (TBP), a general transcription initiation factor. TBP interacts with other protein factors, including high mobility group box 1 (HMGB1), to regulate gene expression. In this study, we examined the effect of TBP Q-tract length on HMGB1 binding using recombinant HMGB1 and N-terminal TBP/Q20~61 proteins. The intracellular association of HMGB1 with TBP was first confirmed by using a half-in vivo co-immunoprecipitation (co-IP) and glutathione S-transferase (GST) pull-down assays in HMGB1 and TBP co-expressed HEK-293 cells. GST pull-down assay using soluble recombinant HMGB1 and TBP/Q20~61 proteins expressed in E. coli also revealed the binding activity between recombinant HMGB1 and TBP. When the binding strength was explored by using a real time quartz crystal microbalance (QCM) assay, a Q-tract length-dependent decrease of HMGB1-TBP interaction was demonstrated. Together with the reported HMGB1-TBP interaction to increase the rate of TBP binding and the stability of the TBP/TATA interaction, our study results suggest that decrease HMGB1 binding to polyQ-expanded TBP may contribute to the pathogenesis of SCA17.