Phosphorylation by Protein Kinase CK2 Changes the DNA Binding Properties of the Human Chromatin Protein DEK
Abstract
Phosphorylation by Protein Kinase CK2 Changes the DNA Binding Properties of the Human Chromatin Protein DEK Ferdinand Kappes 1 , * , Catalina Damoc 2 , Rolf Knippers 1 , Michael Przybylski 2 , Lorenzo A. Pinna 3 and Claudia Gruss 1 1 Department of Biology 2 Department of Chemistry, University of Konstanz, 78457 Konstanz, Federal Republic of Germany 3 Department of Biological Chemistry, University of Padua, Padua, Italy ABSTRACT We have examined the posttranslational modification of the human chromatin protein DEK and found that DEK is phosphorylated by the protein kinase CK2 in vitro and in vivo. Phosphorylation sites were mapped by quadrupole ion trap mass spectrometry and found to be clustered in the C-terminal region of the DEK protein. Phosphorylation fluctuates during the cell cycle with a moderate peak during G 1 phase. Filter binding assays, as well as Southwestern analysis, demonstrate that phosphorylation weakens the binding of DEK to DNA. In vivo, however, phosphorylated DEK remains on chromatin. We present evidence that phosphorylated DEK is tethered to chromatin throughout the cell cycle by the un- or underphosphorylated form of DEK.