To examine whether TAF7 could be phosphorylated by DNA-PKcs directly. An in vitro kinase assays were performed. Firstly, human DNA-PKcs was purified from TGF1 treated HK2 cells by immunoprecipitation with a DNA-PKcs antibody (abcam) and IgG was used as a negative control. The purified proteins and human GST-TAF7 (purchased from proteintech) were incubated in kinase assay buffer (50 mM Tris-HCl, pH 7.5, 150 mM NaCl, 10 mM MgCl2, and 1 mM MnCl2) supplemented with 200 M ATP in 50 l reactions for 30 min at 30°C. Then, phosphorylation of TAF7 was analyzed by mass spectrometry (MS)