p53 modulates the activity of the GLI1 oncogene through interactions with the shared coactivator TAF9

•TAF9 interacts with the oncogenic GLI family members GLI1 and GLI2 but not GLI3.•Removal of the GLI1 TAF9-binding domain reduced cell transformation by GLI1.•GLI-TAF9 binding appears important for oncogenic activity.•p53 binds TAF9 with greater affinity than does GLI1.•p53 sequesters TAF9 from GLI1, providing a mechanism for the GLI1-p53 inhibitory loop