p53 modulates the activity of the GLI1 oncogene through interactions with the shared coactivator TAF9.
The GLI1 oncogene and p53 tumor suppressor gene function in an inhibitory loop that controls stem cell and tumor cell numbers. Since GLI1 and p53 both interact with the coactivator TATA Binding Protein Associated Factor 9 (TAF9), we hypothesized that competition between these transcription factors for TAF9 in cancer cells may contribute to the inhibitory loop and directly affect GLI1 function and cellular phenotype. We showed that TAF9 interacts with the oncogenic GLI family members GLI1 and GLI2 but not GLI3 in cell-free pull-down assays and with GLI1 in rhabdomyosarcoma and osteosarcoma cell lines. Removal of the TAF9-binding acidic alpha helical transactivation domain of GLI1 produced a significant reduction in the ability of GLI1 to transform cells. We then introduced a point mutation into GLI1 (L1052I) that eliminates TAF9 binding and a point mutation into GLI3 (I1510L) that establishes binding. Wild-type and mutant GLI proteins that bind TAF9 showed enhanced transactivating and cell transforming activity compared with those that did not. Therefore, GLI-TAF9 binding appears important for oncogenic activity. We then determined whether wild-type p53 down-regulates GLI function by sequestering TAF9. We showed that p53 binds TAF9 with greater affinity than does GLI1 and that co-expression of p53 with GLI1 or GLI2 down-regulated GLI-induced transactivation, which could be abrogated using mutant forms of GLI1 or p53. This suggests that p53 sequesters TAF9 from GLI1, which may contribute to inhibition of GLI1 activity by p53 and potentially impact therapeutic success of agents targeting GLI-TAF9 interactions in cancer.
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA.
Joon Won
JW
Yoon
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA.
Marilyn
M
Lamm
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA.
Stephen
S
Iannaccone
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA.
Nicole
N
Higashiyama
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA.
King Fu
KF
Leong
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA.
Philip
P
Iannaccone
Developmental Biology Program of the Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA. Electronic address: d-walterhouse@northwestern.edu.
David
D
Walterhouse
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D035381:TATA-Binding Protein Associated Factors / Q000235:genetics / Q000378:metabolism*; D035362:Transcription Factor TFIID / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2; D000074290:Zinc Finger Protein Gli3
C400551:GLI1 protein, human; C082593:GLI2 protein, human; C065683:GLI3 protein, human; D051741:Kruppel-Like Transcription Factors; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C106849:TAF9 protein, human; D035381:TATA-Binding Protein Associated Factors; C495901:TP53 protein, human; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2; D000074290:Zinc Finger Protein Gli3
Coactivator; GLI1; TAF9; p53