Cloning and Biochemical Characterization of TAF-172, a Human Homolog of Yeast Mot1

ABSTRACT

The TATA binding protein (TBP) is a central component of the eukaryotic transcriptional machinery and is the target of positive and negative transcriptional regulators. Here we describe the cloning and biochemical characterization of an abundant human TBP-associated factor (TAF-172) which is homologous to the yeast Mot1 protein and a member of the larger Snf2/Swi2 family of DNA-targeted ATPases. Like Mot1, TAF-172 binds to the conserved core of TBP and uses the energy of ATP hydrolysis to dissociate TBP from DNA (ADI activity). Interestingly, ATP also causes TAF-172 to dissociate from TBP, which has not been previously observed with Mot1. Unlike Mot1, TAF-172 requires both TBP and DNA for maximal (∼100-fold) ATPase activation. TAF-172 inhibits TBP-driven RNA polymerase II and III transcription but does not appear to affect transcription driven by TBP-TAF complexes. As it does with Mot1, TFIIA reverses TAF-172-mediated repression of TBP. Together, these findings suggest that human TAF-172 is the functional homolog of yeast Mot1 and uses the energy of ATP hydrolysis to remove TBP (but apparently not TBP-TAF complexes) from DNA.

ACKNOWLEDGMENTS

We thank W. Herr and R. Tjian for supplying the cDNA libraries used in the cloning, D. Reinberg for the P.3 used in the isolation of TAF-172, and R. Meyers and P. Sharp for supplying the B-TFIID fraction. We thank members of the Pugh and Auble laboratories for many fruitful discussions.

This work was supported by grants from the National Institutes of Health (GM47855 to B.F.P. and GM55763 to D.T.A.), the Searle Scholars Program/The Chicago Community Trust (B.F.P.), and the Leukemia Society of America (B.F.P.).