ABT1 (activator of basal transcription 1) is a nuclear protein that functions in both transcriptional regulation and ribosome biogenesis. ABT1 enhances RNA polymerase II-directed basal transcription by binding to the TATA-binding protein (TBP) and DNA 1. The protein localizes to both the nucleolus and nucleoplasm, consistent with dual roles in transcription and pre-rRNA processing 1. ABT1 physically interacts with IGHMBP2, a UPF1-like helicase, significantly enhancing its ATPase and helicase activities and processivity 2. The IGHMBP2/ABT1 complex associates with the 47S pre-rRNA 5' external transcribed spacer and U3 snoRNA, indicating involvement in pre-rRNA processing 2. ABT1 also associates with tRNAs, particularly tRNA(Tyr), and interacts with transcription factor IIIC-220 and ribosome biogenesis helicases Reptin and Pontin, suggesting a role in the translational machinery 3. Clinically, ABT1 serves as a disease modifier for SMARD1, with intracerebroventricular injection of ABT1 significantly increasing lifespan and reducing neuromuscular junction denervation in mouse models 2. ABT1's activity is negatively regulated by ABTAP, which disrupts ABT1-TBP interactions and suppresses transcriptional activation 1.