MDMX contains an autoinhibitory sequence element
MDMX contains an autoinhibitory sequence element
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DOI：
10.1073/pnas.1317398110
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发表时间：
2013-10-29
影响因子：
11.1
通讯作者：
Fersht, Alan R.
中科院分区：
文献类型：
--
作者：
Bista, Michal;Petrovich, Miriana;Fersht, Alan R.
MDM2 和 MDMX 是与 p53 结合并调节其活性的同源蛋白。两者都包含三个折叠结构域，并且类似于 70% 的本质无序区域。先前详细的结构和生物物理研究集中在孤立的折叠域上。两者的 N 端结构域均对 p53 (p53TAD) 的无序 N 端表现出高亲和力，并抑制其反式激活功能。在这里，我们研究了全长 MDMX，发现对 p53TAD 的亲和力比其分离的 N 端结构域弱 100 倍。我们从 NMR 波谱和结合研究中发现，MDMX（但不是 MDM2）含有保守的、无序的自抑制元件，可在分子内竞争与 p53TAD 的结合。这个基序，我们称之为 WWW 元件，以残基 Trp200 和 Trp201 为中心。该元件的删除或突变增加了 MDMX 与分离的 N 端结构域水平的结合亲和力。 MDMX 的自我抑制意味着其活性的调节变构机制。 MDMX 处于潜伏状态，其中其与 p53TAD 的结合活性被自身抑制所掩盖。 MDMX 的激活需要与调节蛋白结合。 WWW 元件的抑制功能可以解释 MDMX 的选择性剪接变体的致癌作用，该变体不包含 WWW 元件，并且存在于一些侵袭性癌症中。
MDM2 and MDMX are homologous proteins that bind to p53 and regulate its activity. Both contain three folded domains and similar to 70% intrinsically disordered regions. Previous detailed structural and biophysical studies have concentrated on the isolated folded domains. The N-terminal domains of both exhibit high affinity for the disordered N-terminal of p53 (p53TAD) and inhibit its transactivation function. Here, we have studied full-length MDMX and found a similar to 100-fold weaker affinity for p53TAD than does its isolated N-terminal domain. We found from NMR spectroscopy and binding studies that MDMX (but not MDM2) contains a conserved, disordered self-inhibitory element that competes intramolecularly for binding with p53TAD. This motif, which we call the WWW element, is centered around residues Trp200 and Trp201. Deletion or mutation of the element increased binding affinity of MDMX to that of the isolated N-terminal domain level. The self-inhibition of MDMX implies a regulatory, allosteric mechanism of its activity. MDMX rests in a latent state in which its binding activity with p53TAD is masked by autoinhibition. Activation of MDMX would require binding to a regulatory protein. The inhibitory function of the WWW element may explain the oncogenic effects of an alternative splicing variant of MDMX that does not contain the WWW element and is found in some aggressive cancers.