Extended String Binding Mode of the Phosphorylated Transactivation Domain of Tumor Suppressor p53

Abstract

The transactivation domain (TAD) of tumor suppressor p53 has homologous subdomains, TAD1 and TAD2. Both are intrinsically disordered in their free states, but all structures of TAD1 and TAD2 bound to their target proteins have demonstrated use of an amphipathic α-helix, suggesting that the binding-coupled helix folding mechanism of TAD1 and TAD2 is essential. Although phosphorylation of TAD is important to switch the function of p53, bound structures of phosphorylated TAD1 and TAD2 have not been determined. Here, we reveal the recognition mechanism of the phosphorylated TAD2 bound to a pleckstrin homology (PH) domain from human TFIIH subunit p62 in an extended string-like conformation. This string-like binding mode of TAD2 seems to be independent of its phosphorylation in spite of enhanced binding activity upon phosphorylation. This is in contrast to the amphipathic helical binding mode of the unphosphorylated TAD2 to the yeast tfb1 PH domain and demonstrates that the p53 TAD2 has much higher conformational malleability than previously appreciated.

Recognition of the disordered p53 transactivation domain by the transcriptional adapter zinc finger domains of CREB-binding protein

“…A similar AD2 structure is observed in the complex with HMGB1, although the helix is somewhat shorter (64). Somewhat surprisingly, given the strong propensity of AD2 to fold into a helix, a doubly phosphorylated p53 AD2 motif binds in a more extended conformation to a highly electropositive region of the PH domain of human TFIIH p62 (65).…”

Structural Insight into the Mechanism of TFIIH Recognition by the Acidic String of the Nucleotide Excision Repair Factor XPC

“…In addition to XPC, the p62 PH domain binds to an acidic domain of the general transcription factor TFIIEa Okuda et al, 2008), the transactivation domain (TAD) of the tumor suppressor p53 (Di Lello et al, 2006;Okuda and Nishimura, 2014). Although various partners of the p62 PH domain have been identified (Di Lello et al, 2005;Iyer et al, 1996;Mas et al, 2011), only two tertiary structures of the human p62 PH domain bound to the TFIIEa acidic domain (Okuda et al, 2008) and phosphorylated p53 TAD (Okuda and Nishimura, 2014) have been reported.…”

<b>Prevalence of low-penetrant germline </b><i><b>TP53</b></i><b> D49H mutation in Japanese cancer </b><b>patients </b>

“…Lee et al demonstrated that the transactivation domain 2 of p53 protein forms a complex with CREB binding protein, and that a salt bridge between D49 of p53 protein and R2105 of nuclear coactivator binding domain of CREB binding protein may contribute to the binding specificity (11). Okuda and Nishimura suggested that the transactivation domain 2 of p53 protein binds the human TFIIH subunit p62 in an extended string-like conformation; they claimed that two phosphorylation sites, S46 and T55, play an important role (14) . It is worth noting that D49 locates between these amino acids.…”