Nucleic Acids Research Advance Access originally published online on March 25, 2009
Nucleic Acids Research 2009 37(10):3288-3300; doi:10.1093/nar/gkp197
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2009, Vol. 37, No. 10 3288-3300
© 2009 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.
Gene Regulation, Chromatin and Epigenetics |
CK2 phosphorylation of the PRH/Hex homeodomain functions as a reversible switch for DNA binding
1Institute for Biomedical Research, Birmingham University Medical School, Edgbaston, Birmingham, B15 2TT, UK, 2LBPA (UMR 8113 du CNRS), Ecole Normale Superieur de Cachan, 61 Avenue du President Wilson, 94235 Cachan, France and 3Department of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
* To whom correspondence should be addressed. Tel: +44 0121 414 6820; Email: p.jayaraman{at}bham.ac.uk
Received April 11, 2008. Revised March 10, 2009. Accepted March 11, 2009.
The proline-rich homeodomain protein (PRH/Hex) regulates transcription by binding to specific DNA sequences and regulates mRNA transport by binding to translation initiation factor eIF4E. Protein kinase CK2 plays multiple roles in the regulation of gene expression and cell proliferation. Here, we show that PRH interacts with the β subunit of CK2 in vitro and in cells and that CK2 phosphorylates PRH. Phosphorylation of PRH by CK2 inhibits the DNA binding activity of this protein and dephosphorylation restores DNA binding indicating that this modification acts as a reversible switch. We show that phosphorylation of the homeodomain is sufficient to block DNA binding and we identify two amino acids within this the domain that are phosphorylated by CK2: S163 and S177. Site-directed mutagenesis demonstrates that mutation of either of these residues to glutamic acid partially mimics phosphorylation but is insufficient to completely block DNA binding whereas an S163E/S177E double mutation severely inhibits DNA binding. Significantly, the S163E and S177E mutations and the S163E/S177E double mutation all inhibit the ability of PRH to regulate transcription in cells. Since these amino acids are conserved between many homeodomain proteins, our results suggest that CK2 may regulate the activity of several homeodomain proteins in this manner.