Ho William C, Fitzgerald Mary X, Marmorstein Ronen
The Wistar Institute, Pennsylvania 19104, USA.
J Biol Chem. 2006 Jul 21;281(29):20494-502. doi: 10.1074/jbc.M603634200. Epub 2006 May 22.
The p53 tumor suppressor protein binds to DNA as a dimer of dimers to regulate transcription of genes that mediate responses to cellular stress. We have prepared a cross-linked trapped p53 core domain dimer bound to decamer DNA and have determined its structure by x-ray crystallography to 2.3A resolution. The p53 core domain subunits bind nearly symmetrically to opposite faces of the DNA in a head-to-head fashion with a loophelix motif making sequence-specific DNA contacts and bending the DNA by about 20 degrees at the site of protein dimerization. Protein subunit interactions occur over the central DNA minor groove and involve residues from a zinc-binding region. Analysis of tumor derived p53 mutations reveals that the dimerization interface represents a third hot spot for mutation that also includes residues associated with DNA contact and protein stability. Residues associated with p53 dimer formation on DNA are poorly conserved in the p63 and p73 paralogs, possibly contributing to their functional differences. We have used the dimeric protein-DNA complex to model a dimer of p53 dimers bound to icosamer DNA that is consistent with solution bending data and suggests that p53 core domain dimer-dimer contacts are less frequently mutated in human cancer than intra-dimer contacts.
p53肿瘤抑制蛋白以二聚体的二聚体形式与DNA结合，以调节介导细胞应激反应的基因的转录。我们制备了与十聚体DNA结合的交联捕获p53核心结构域二聚体，并通过X射线晶体学确定了其结构，分辨率为2.3埃。p53核心结构域亚基以头对头的方式几乎对称地结合到DNA的相对面上，带有一个环螺旋基序，与DNA形成序列特异性接触，并在蛋白质二聚化位点使DNA弯曲约20度。蛋白质亚基相互作用发生在中央DNA小沟上，涉及来自锌结合区域的残基。对肿瘤来源的p53突变的分析表明，二聚化界面代表了突变的第三个热点，该热点还包括与DNA接触和蛋白质稳定性相关的残基。与p53在DNA上形成二聚体相关的残基在p63和p73旁系同源物中保守性较差，这可能导致了它们的功能差异。我们使用二聚体蛋白质-DNA复合物对与二十聚体DNA结合的p53二聚体的二聚体进行了建模，该模型与溶液弯曲数据一致，并表明p53核心结构域二聚体-二聚体接触在人类癌症中发生突变的频率低于二聚体内接触。
