Identification of the human DEAD-box protein p68 as a substrate of Tlk1.
The activity of the human protein kinase Tlk1 is down-regulated within minutes after exposure of cells to ionizing radiation. In order to identify signaling pathways which might be relevant in the radiation response of mammalian cells we screened nuclear proteins for substrates of Tlk1. Among several proteins one could be identified as p68 RNA helicase. Furthermore, it could be shown that Tlk1 phosphorylates immunoprecipitated p68. The phosphorylation of the C-terminal fragment of p68 by rTlk1 reduced its affinity to single stranded RNA in a gel shift assay. In addition, it could be demonstrated that increasing the Tlk1 activity in HT1080 cells by forced Tlk1 overexpression leads to an increased phosphorylation of endogenous p68, arguing that p68 might be a physiological substrate of Tlk1. These findings open the possibility that Tlk1 might participate in diverse biologic functions like cell growth and differentiation, pre-mRNA splicing, and transcriptional coactivation.
Kodym
Reinhard
R
Department of Radiobiology, Clinic for Radiotherapy and Radiobiology, Medical University of Vienna, Vienna, Austria. reinhard.kodym@meduniwien.ac.at
Henöckl
Christian
C
Fürweger
Christoph
C
D053487:DEAD-box RNA Helicases; D018922:HL-60 Cells; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020365:RNA Helicases / Q000378:metabolism*
D009687:Nuclear Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; C425323:TLK1 protein, human; C506749:Ddx5 protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases