Abstract
Mot1 is an essential Snf2/Swi2-related Saccharomyces cerevisiae protein that binds the TATA-binding protein (TBP) and removes TBP from DNA using ATP hydrolysis. Mot1 functions in vivo both as a repressor and as an activator of transcription. Mot1 catalysis of TBP.DNA disruption is consistent with its function as a repressor, but the Mot1 mechanism of activation is unknown. To better understand the physiologic role of Mot1 and its enzymatic mechanism, MOT1 mutants were generated and tested for activity in vitro and in vivo. The results demonstrate a close correlation between the TBP.DNA disruption activity of Mot1 and its essential in vivo function. Previous results demonstrated a large overlap in the gene sets controlled by Mot1 and NC2. Mot1 and NC2 can co-occupy TBP.DNA in vitro, and NC2 binding does not impair Mot1-catalyzed disruption of the complex. Residues on the DNA-binding surface of TBP are important for Mot1 binding and the Mot1.TBP binary complex binds very poorly to DNA and does not dissociate in the presence of ATP. However, the binary complex binds DNA well in the presence of the transition state analog ADP-AlF(4). A model for Mot1 action is proposed in which ATP hydrolysis causes the Mot1 N terminus to displace the TATA box, leading to ejection of Mot1 and TBP from DNA.
Highlights
A critical step in the assembly of an active transcription complex at an RNA polymerase II promoter involves recruitment of TATA-binding protein (TBP)1 and TBP-associated factors [1,2,3]
Catalysis of TBP1⁄7DNA disruption requires a grip by Mot1 on both upstream DNA and TBP, the upstream DNA and the TBP1⁄7DNA complex can be conformationally uncoupled without impairing catalysis [13]
These results suggest that ATP hydrolysis causes a change in either the conformation of TBP or the interaction of Mot1 with the DNA-binding surface of TBP and that these ATP-driven conformational changes explain how Mot1 drives disruption of the TBP1⁄7DNA complex
Summary
A critical step in the assembly of an active transcription complex at an RNA polymerase II promoter involves recruitment of TATA-binding protein (TBP)1 and TBP-associated factors [1,2,3]. These results suggest that ATP hydrolysis causes a change in either the conformation of TBP or the interaction of Mot1 with the DNA-binding surface of TBP and that these ATP-driven conformational changes explain how Mot1 drives disruption of the TBP1⁄7DNA complex.
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