McKinney Kristine, Mattia Melissa, Gottifredi Vanesa, Prives Carol
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
Mol Cell. 2004 Nov 5;16(3):413-24. doi: 10.1016/j.molcel.2004.09.032.
In cells, sequence-specific transcription factors must search through an entire genome to find their target sites in promoters. Such sites may be identified by using one-dimensional (linear diffusion) and/or three-dimensional (association/dissociation) mechanisms. We show here that wild-type p53 possesses the ability to linearly diffuse on DNA. p53 lacking its C terminus is incapable of such sliding along DNA, while the isolated C terminus of p53 is even more effective than the full-length protein at one-dimensional linear diffusion. Importantly, neither acetylation-mimicking mutations nor phosphorylation of residues within the C terminus stimulates linear diffusion by p53. Supporting these in vitro observations, we found that C-terminally deleted p53 (p53Delta30) expressed at physiological levels is deficient in binding to and transactivating downstream promoters in vivo. Therefore, our data show that the C terminus is a positive regulator of DNA binding in vivo and in vitro, and indicate that the mechanism may involve linear diffusion.
在细胞中，序列特异性转录因子必须在整个基因组中进行搜索，以找到其在启动子中的靶位点。此类位点可通过一维（线性扩散）和/或三维（结合/解离）机制来识别。我们在此表明，野生型p53具有在DNA上进行线性扩散的能力。缺少C末端的p53无法沿DNA进行此类滑动，而p53的分离C末端在一维线性扩散方面甚至比全长蛋白更有效。重要的是，无论是模拟乙酰化的突变还是C末端内残基的磷酸化都不会刺激p53的线性扩散。支持这些体外观察结果的是，我们发现以生理水平表达的C末端缺失型p53（p53Delta30）在体内与下游启动子的结合及反式激活方面存在缺陷。因此，我们的数据表明，C末端在体内和体外都是DNA结合的正调节因子，并表明该机制可能涉及线性扩散。
