Mechanism of TAp73 inhibition by ΔNp63 and structural basis of p63/p73 hetero-tetramerization
Mechanism of TAp73 inhibition by ΔNp63 and structural basis of p63/p73 hetero-tetramerization
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DOI：
10.1038/cdd.2016.83
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发表时间：
2016-12-01
影响因子：
12.4
通讯作者：
Doetsch, Volker
中科院分区：
文献类型：
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作者：
Gebel, Jakob;Luh, Laura M.;Doetsch, Volker
p53肿瘤抑制家族的成员以多种亚型表达。具有N-末端反式激活结构域的同种型具有转录活性，而缺乏该结构域的同种型通常抑制其他家族成员的转录活性。在鳞状细胞癌中，Delta Np 63 α的高表达水平抑制了TAp 73 β的肿瘤抑制功能。原则上，这可能是由于启动子的阻断或两种蛋白质之间的直接相互作用。p63和p73可以通过它们的四聚化结构域异源寡聚化，并且由两个p63和两个p73分子组成的异源四聚体在化学上比两个同源四聚体更稳定。在这里，我们表明，表达p63和p73的细胞存在于小鼠表皮和毛囊中，异源四聚体复合物可以通过免疫沉淀法在分化的角质形成细胞中检测到。通过对异源四聚体的结构测定，我们揭示了为什么异源四聚体是生物学上优选的物种。我们已经创建了专门形成异源四聚体或同源四聚体的突变体，从而可以研究这些p63/p73异源四聚体的功能。使用这些工具，我们表明鳞状细胞癌中TAp 73 β的抑制是由于启动子抑制而不是直接相互作用。
Members of the p53 tumor-suppressor family are expressed as multiple isoforms. Isoforms with an N-terminal transactivation domain are transcriptionally active, while those ones lacking this domain often inhibit the transcriptional activity of other family members. In squamous cell carcinomas, the high expression level of Delta Np63 alpha inhibits the tumor-suppressor function of TAp73 beta. This can in principle be due to blocking of the promoter or by direct interaction between both proteins. p63 and p73 can hetero-oligomerize through their tetramerization domains and a hetero-tetramer consisting of two p63 and two p73 molecules is thermodynamically more stable than both homo-tetramers. Here we show that cells expressing both p63 and p73 exist in mouse epidermis and hair follicle and that hetero-tetramer complexes can be detected by immunoprecipitation in differentiating keratinocytes. Through structure determination of the hetero-tetramer, we reveal why this hetero-tetramer is the thermodynamically preferred species. We have created mutants that exclusively form either hetero-tetramers or homo-tetramers, allowing to investigate the function of these p63/p73 hetero-tetramers. Using these tools, we show that inhibition of TAp73 beta in squamous cell carcinomas is due to promoter squelching and not direct interaction.