Critical roles for the serine 20, but not the serine 15, phosphorylation site and for the polyproline domain in regulating p53 turnover
Critical roles for the serine 20, but not the serine 15, phosphorylation site and for the polyproline domain in regulating p53 turnover
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DOI：
10.1042/0264-6021:3590459
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发表时间：
2001-10-15
影响因子：
4.1
通讯作者：
Meek, DW
中科院分区：
文献类型：
--
作者：
Dumaz, N;Milne, DM;Meek, DW
P53肿瘤抑制蛋白是一种短暂的转录因子，在广泛的细胞压力下会变得稳定。泛素化和蛋白酶体对p53的靶向降解是由p53的负调控伙伴MDM2(小鼠双分钟克隆2)介导的。先前的研究表明，DNA损伤诱导的关键N端P53的磷酸化在调节与MDM2的相互作用中起着关键作用，但丝氨酸15和20的确切作用尚不清楚。在这里，我们表明丝氨酸15和其他一系列关键的N末端磷酸化位点被丙氨酸取代，而丙氨酸不能被磷酸化，对全长人类p53的泛素化和降解几乎没有影响。相反，丝氨酸20的替代使p53对MDM2介导的周转高度敏感。这些结果定义了丝氨酸15和20的不同作用，这两个位点以前被证明依赖于通过DNA损伤和ATM(共济失调毛细血管扩张突变)介导的机制的磷酸化。我们还表明，P53的多聚赖氨酸区域，在P53诱导的细胞凋亡中起关键作用的区域，对MDM2介导的P53的周转起着关键的影响。
The p53 tumour suppressor protein is a short-lived transcription factor that becomes stabilized in response to a wide range of cellular stresses. Ubiquitination and the targeting of p53 for degradation by the proteasome are mediated by Mdm2 (mouse double minute clone 2), a negative regulatory partner of p53. Previous studies have suggested that DNA-damage-induced phosphorylation of p53 at key N-terminal sites has a pivotal role in regulating the interaction with Mdm2 but the precise role of phosphorylation of serines 15 and 20 is still unclear. Here we show that replacement of serine 15 and a range of other key N-terminal phosphorylation sites with alanine, which cannot be phosphorylated, has little effect on the ubiquitination and degradation of full-length human p53. In contrast, replacement of serine 20 makes p53 highly sensitive to Mdm2-mediated turnover. These results define distinct roles for serines 15 and 20, two sites previously demonstrated to be dependent on phosphorylation through mechanisms mediated by DNA damage and ATM (ataxia telangiectasia mutated). We also show that the polyproline region of p53, a domain that has a key role in p53-induced apoptosis, exerts a critical influence over the Mdm2-mediated turnover of p53.