Martinez J D, Craven M T, Pennington M E
Department of Radiation Oncology, University of Arizona, Tuscon 85724, USA.
Oncogene. 1998 Jan 29;16(4):453-8. doi: 10.1038/sj.onc.1201565.
The p53 tumor suppressor protein binds two copies of a ten base pair motif that is degenerate in eight out of ten bases and conforms to the sequence, 5'PuPuPuC(A/T)(T/A)GPyPyPy-3'. As a consequence of this high degree of degeneracy, p53 response elements show a great deal of variation and it has been speculated that the variation aids in the selective activation of p53 responsive genes by specific stimuli. Here, we examined the DNA binding characteristics of several different p53 protein complexes present in nuclear extracts prepared from a cell line expressing the murine temperature sensitive p53 protein, p53val135. Interestingly, the complexes exhibited a distinct preference for binding to some p53 response elements and not others. A critical determinant of this specificity was the sequence at the center of the ten base pair motif and alteration of a single base within this region was sufficient to alter the set of complexes that associated with the oligonucleotide. In addition, thermal denaturation experiments demonstrated that some complexes could bind DNA even though the p53val135 protein had a mutant conformation. Our results are consistent with the hypothesis that p53 can distinguish between various response elements and suggest that this selectivity is manifested, in part, by the sequence of the motif and conformation of the p53 protein.
p53肿瘤抑制蛋白结合两个十碱基对基序的拷贝，该基序在十个碱基中有八个是简并的，符合5'PuPuPuC(A/T)(T/A)GPyPyPy-3'的序列。由于这种高度的简并性，p53反应元件表现出很大的变异性，有人推测这种变异性有助于特定刺激对p53反应基因的选择性激活。在这里，我们研究了从表达鼠温度敏感型p53蛋白p53val135的细胞系制备的核提取物中存在的几种不同p53蛋白复合物的DNA结合特性。有趣的是，这些复合物对某些p53反应元件表现出明显的结合偏好，而对其他元件则不然。这种特异性的一个关键决定因素是十碱基对基序中心的序列，该区域内单个碱基的改变足以改变与寡核苷酸结合的复合物的组合。此外，热变性实验表明，即使p53val135蛋白具有突变构象，一些复合物仍能结合DNA。我们的结果与p53可以区分各种反应元件的假设一致，并表明这种选择性部分地由基序序列和p53蛋白的构象表现出来。
