Secondary interaction between MDMX and p53 core domain inhibits p53 DNA binding.
The MDMX oncoprotein is an important regulator of tumor suppressor p53 activity during embryonic development. Despite sequence homology to the ubiquitin E3 ligase MDM2, MDMX depletion activates p53 without significant increase in p53 level, implicating a degradation-independent mechanism. We present evidence that MDMX inhibits the sequence-specific DNA binding activity of p53. This function requires the cooperation between MDMX and CK1α, and phosphorylation of S289 on MDMX. Depletion of MDMX or CK1α increases p53 DNA binding without stabilization of p53. A proteolytic fragment release assay revealed that in the MDMX-p53 complex, the MDMX acidic domain and RING domain interact stably with the p53 DNA binding domain. These interactions are referred to as secondary interactions because they only occur after the canonical-specific binding between the MDMX and p53 N termini, but exhibit significant binding stability in the mature complex. CK1α cooperates with MDMX to inhibit p53 DNA binding by further stabilizing the MDMX acidic domain and p53 core domain interaction. These results suggest that secondary intermolecular interaction is important in p53 regulation by MDMX, which may represent a common phenomenon in complexes containing multidomain proteins.
Department of Molecular Oncology, Moffitt Cancer Center, Tampa, FL 33612; Department of Diagnostic and Therapeutic Ultrasonography, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China;
Xi
X
Wei
Department of Neuro Oncology, MD Anderson Cancer Center, Houston, TX 77030;
Shaofang
S
Wu
Department of Molecular Oncology, Moffitt Cancer Center, Tampa, FL 33612;
Tanjing
T
Song
Department of Molecular Oncology, Moffitt Cancer Center, Tampa, FL 33612;
Lihong
L
Chen
Department of Thyroid and Cervical Tumor, Tianjin Medical University Cancer Institute and Hospital, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China;
Ming
M
Gao
Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620; Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33620.
Wade
W
Borcherds
Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620; Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33620.
Gary W
GW
Daughdrill
Department of Molecular Oncology, Moffitt Cancer Center, Tampa, FL 33612; jiandong.chen@moffitt.org.
Jiandong
J
Chen
D001665:Binding Sites; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D004273:DNA, Neoplasm / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D009369:Neoplasms / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D000072417:Protein Domains; D025941:Protein Interaction Mapping / Q000379:methods; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism*
D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53
CK1α; DNA binding; MDMX; p53; secondary interaction