May constitute a novel regulatory system for basal transcription. Negatively regulates ABT1. Interacts with ABT1. Forms a complex with ABT1 and suppresses the ABT1-induced activation of polymerase II-directed transcription in mammalian cells. Disrupts the interaction between ABT1 and TATA-binding protein (TBP), and suppresses the ABT1-induced activation of polymerase II-directed basal transcription in vitro. Is concomitantly relocalized into discrete nuclear bodies at higher expression. Ubiquitously expressed. Belongs to the ESF1 family.