Transcriptional coactivator that stimulates GCN4-dependent transcriptional activity by bridging the DNA-binding region of GCN4 and TBP (SPT15), thereby recruiting TBP to GCN4-bound promoters. Interacts with TBP and the transcription factor GCN4. Present with 47277 molecules/cell in log phase SD medium. Belongs to the MBF1 family.