Structural convergence of unstructured p53 family transactivation domains in MDM2 recognition

• Published in: Cell cycle (Georgetown, Tex.) Vol. 14; no. 4; pp. 533 - 543
• Main Authors: Shin, Jae-Sun, Ha, Ji-Hyang, Lee, Dong-Hwa, Ryu, Kyoung-Seok, Bae, Kwang-Hee, Park, Byoung Chul, Park, Sung Goo, Yi, Gwan-Su, Chi, Seung-Wook
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 15.02.2015
• Subjects: Amino Acid Sequence; Circular Dichroism; DNA-Binding Proteins - genetics; Gene Components; Humans; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Sequence Data; Multiprotein Complexes - genetics; Nuclear Proteins - genetics; Protein Binding; Protein Conformation; Proto-Oncogene Proteins c-mdm2 - genetics; Transcription Factors - genetics; Transcriptional Activation - genetics; Tumor Protein p73; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Proteins - genetics; HSQC, heteronuclear single quantum coherence; IDP, Intrinsically disordered protein; complex structure; transactivation domain; RDC, Residual dipolar coupling; NOESY, nuclear Overhauser effect spectroscopy; p73; ITC, Isothermal titration calorimetry; TAD, transactivation domain; NMR; AIRs, Ambiguous interaction restraints; NMR, nuclear magnetic resonance; MDM2; MDM2, mouse double minute 2; p53 family
• ISSN: 1538-4101; 1551-4005; 1551-4005
• DOI: 10.1080/15384101.2014.998056

The p53, p63, and p73 proteins belong to the p53 family of transcription factors, which play key roles in tumor suppression. Although the transactivation domains (TADs) of the p53 family are intrinsically disordered, these domains are commonly involved in the regulatory interactions with mouse double minute 2 (MDM2). In this study, we determined the solution structure of the p73TAD peptide in complex with MDM2 using NMR spectroscopy and biophysically characterized the interactions between the p53 family TAD peptides and MDM2. In combination with mutagenesis data, the complex structures revealed remarkably close mimicry of the MDM2 recognition mechanism among the p53 family TADs. Upon binding with MDM2, the intrinsically disordered p73TAD and p63TAD peptides adopt an amphipathic α-helical conformation, which is similar to the conformation of p53TAD, although the α-helical content induced by MDM2 binding varies. With isothermal titration calorimetry (ITC) and circular dichroism (CD) data, our biophysical characterization showed that p73TAD resembles p53TAD more closely than p63TAD in terms of helical stability, MDM2 binding affinity, and phosphorylation effects on MDM2 binding. Therefore, our structural information may be useful in establishing alternative anticancer strategies that exploit the activation of the p73 pathway against human tumors bearing p53 mutations.