Structural and Functional Characterization of a Phosphatase Domain within Yeast General Transcription Factor IIIC

This is the authors' abstract. We don't add key points for this paper.

Saccharomyces cerevisiae τ55, a subunit of the RNA polymerase III-specific general transcription factor TFIIIC, comprises an N-terminal histidine phosphatase domain (τ55-HPD) whose catalytic activity and cellular function is poorly understood. We solved the crystal structures of τ55-HPD and its closely related paralogue Huf and used in silico docking methods to identify phosphoserine- and phosphotyrosine-containing peptides as possible substrates that were subsequently validated using in vitro phosphatase assays. A comparative phosphoproteomic study identified additional phosphopeptides as possible targets that show the involvement of these two phosphatases in the regulation of a variety of cellular functions. Our results identify τ55-HPD and Huf as bona fide protein phosphatases, characterize their substrate specificities, and provide a small set of regulated phosphosite targets in vivo . Background: Subunit τ55 of TFIIIC contains a phosphatase domain of unknown function. Results: Crystal structures of the τ55 phosphatase domain and its paralogue Huf, in silico docking, in vitro candidate approaches, and in vivo phosphoproteomics identified phosphopeptides as substrates. Conclusion: τ55-HPD and Huf hydrolyze phosphopeptides in proteins of different cellular functions. Significance: Protein phosphatase activities of τ55 and Huf contribute to regulating metabolic networks.