Nucleic Acids Research Advance Access originally published online on December 15, 2007
Nucleic Acids Research 2008 36(3):793-802; doi:10.1093/nar/gkm1093
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Nucleic Acids Research, 2008, Vol. 36, No. 3 793-802
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Site specific phosphorylation of yeast RNA polymerase I
1Institut für Biochemie, Mikrobiologie und Genetik, Universität Regensburg and 2Gene Center Munich and Center for integrated Protein Science CiPS M, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
*To whom correspondence should be addressed. Tel: +49 941 943 2472; Fax: +49 941 943 2474; Email: herbert.tschochner{at}vkl.uni-regensburg.de
Received October 29, 2007. Revised November 22, 2007. Accepted November 22, 2007.
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.