Site specific phosphorylation of yeast RNA polymerase I

Abstract

All nuclear RNA polymerases are phosphoprotein complexes. Yeast RNA polymerase I (Pol I) contains approximately 15 phosphate groups, distributed to 5 of the 14 subunits. Information about the function of the single phosphosites and their position in the primary, secondary and tertiary structure is lacking. We used a rapid and efficient way to purify yeast RNA Pol I to determine 13 phosphoserines and -threonines. Seven of these phosphoresidues could be located in the 3D-homology model for Pol I, five of them are more at the surface. The single phosphorylated residues were systematically mutated and the resulting strains and Pol I preparations were analyzed in cellular growth, Pol I composition, stability and genetic interaction with non-essential components of the transcription machinery. Surprisingly, all Pol I phosphorylations analyzed were found to be non-essential post-translational modifications. However, one mutation (subunit A190 S685D) led to higher growth rates in the presence of 6AU or under environmental stress conditions, and was synthetically lethal with a deletion of the Pol I subunit A12.2, suggesting a role in RNA cleavage/elongation or termination. Our results suggest that individual major or constitutively phosphorylated residues contribute to non-essential Pol I-functions.

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@inproceedings{Gerber2008SiteSP, title={Site specific phosphorylation of yeast RNA polymerase I}, author={Jochen Gerber and Alarich Reiter and Robert Steinbauer and Steffen Jakob and Claus-Dieter Kuhn and Patrick Cramer and Joachim Griesenbeck and Philipp Milkereit and Herbert Tschochner}, booktitle={Nucleic acids research}, year={2008} }