Two Distinct Motifs within the p53 Transactivation Domain Bind to the Taz2 Domain of p300 and Are Differentially Affected by Phosphorylation

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• 作者：Lisa M. Miller Jenkins ; Hiroshi Yamaguchi ; Ryo Hayashi ; Scott Cherry ; Joseph E. Tropea ; Maria Miller ; Alexander Wlodawer ; Ettore Appella ; Sharlyn J. Mazur
• 刊名：Biochemistry
• 出版年：2009
• 出版时间：February 17, 2009
• 年：2009
• 卷：48
• 期：6
• 页码：1244-1255
• 全文大小：257K
• 年卷期：v.48,no.6(February 17, 2009)
• ISSN：1520-4995

文摘

The tumor suppressor p53 functions as a transcriptional activator for many genes, including several key genes involved in cell cycle arrest and apoptosis. Following DNA damage-induced stress, p53 undergoes extensive posttranslational modification, resulting in increased stability and activity. Two critical cofactors for p53-mediated transactivation are the histone acetyltransferase paralogues CREB-binding protein (CBP) and p300. The N-terminal transactivation domain of p53 interacts with several domains of CBP/p300, including the Taz2 domain. Here, we report the effects of specific p53 phosphorylations on its interaction with the Taz2 domain of p300. Using a competitive fluorescence anisotropy assay, we determined that monophosphorylation of p53 at Ser₁₅ or Thr₁₈ increased the affinity of p53(1−39) for Taz2, and diphosphorylations at Ser₁₅ and Ser₃₇ or Thr₁₈ and Ser₂₀ further increased the affinity. In addition, we identified a second binding site for Taz2 within p53 residues 35−59. This second site bound Taz2 with a similar affinity as the first site, but the binding was unaffected by phosphorylation. Thus, p53 posttranslational modification modulates only one of the two binding sites for p300 Taz2. Further investigation of Taz2 binding to p53(1−39) or p53(35−59) by isothermal titration calorimetry indicated that upon complex formation, the change in heat capacity at constant pressure, ΔC_p, was negative for both sites, suggesting the importance of hydrophobic interactions. However, the more negative value of ΔC_p for Taz2 binding to the first (−330 cal/(mol·K)) compared to the second site (−234 cal/(mol·K)) suggests that the importance of nonpolar and polar interactions differs between the two sites.