Loughery Jayne, Cox Miranda, Smith Linda M, Meek David W
Division of Cancer Research, Medical Research Institute, The University of Dundee, Ninewells Hospital, James Arrott Drive, Dundee DD1 9SY, United Kingdom.
Division of Cancer Research, Medical Research Institute, The University of Dundee, Ninewells Hospital, James Arrott Drive, Dundee DD1 9SY, United Kingdom
Nucleic Acids Res. 2014 Jul;42(12):7666-80. doi: 10.1093/nar/gku501. Epub 2014 Jun 13.
The p53 tumour suppressor is induced by various stress stimuli and coordinates an adaptive gene expression programme leading to growth arrest or cell death. Some stimuli, such as DNA damage, lead to rapid and substantial multisite phosphorylation of p53, nucleated initially through phosphorylation of serine 15. Other stimuli, such as hyper-proliferation, do not stimulate p53-phosphorylation, raising questions regarding the physiological role for phosphorylation. Here, we show that a basal level of Ser15 phosphorylation occurs in both unstimulated cells and cells stimulated pharmacologically to induce p53. p53 in which Ser15 is substituted by alanine (S15A) fails to mediate p53-dependent transcription or growth arrest but can be rescued by substitution with aspartate (S15D: a phospho-mimic). Chromatin immunoprecipitation (ChIP) analyses show that, while wt- and S15A-p53 are detectable on the CDKN1A (p21) promoter (as a representative p53-responsive promoter), S15A-p53 does not stimulate histone acetylation (a measure of chromatin relaxation), nor is its recruitment stimulated, in response to a DNA damage or pharmacological stimulus. These data demonstrate that Ser15 phosphorylation is required for p53 function in the physiological context of p53-responsive promoters and suggest a key and possibly universal role even for low levels of this modification in promoting p53-transcription function.
p53肿瘤抑制因子可由多种应激刺激诱导产生，并协调一个适应性基因表达程序，从而导致细胞生长停滞或死亡。某些刺激，如DNA损伤，会导致p53迅速发生大量多位点磷酸化，最初是通过丝氨酸15的磷酸化引发的。而其他刺激，如过度增殖，则不会刺激p53磷酸化，这引发了关于磷酸化生理作用的问题。在此，我们表明，在未受刺激的细胞以及经药物刺激诱导p53的细胞中，均存在基础水平的丝氨酸15磷酸化。丝氨酸15被丙氨酸取代（S15A）的p53无法介导p53依赖性转录或生长停滞，但用天冬氨酸取代（S15D：一种磷酸化模拟物）则可使其恢复功能。染色质免疫沉淀（ChIP）分析表明，虽然野生型p53和S15A-p53在CDKN1A（p21）启动子（作为一个代表性的p53反应性启动子）上均可检测到，但S15A-p53不会刺激组蛋白乙酰化（一种染色质松弛的指标），在DNA损伤或药物刺激下，其募集也不会受到刺激。这些数据表明，在p53反应性启动子的生理背景下，丝氨酸15磷酸化是p53发挥功能所必需的，这表明即使是低水平的这种修饰在促进p53转录功能方面也可能发挥关键且普遍的作用。
