锌指蛋白Miz1磷酸化对其泛素化作用的影响研究

Effect of Phosphorylation by Akt on Miz1's Ubiquitination

蛋白的磷酸化与其泛素化作用有着广泛而密切的联系。有研究报道,在DNA损伤的情况下,蛋白激酶Akt能磷酸化转录因子Miz1,参与细胞周期停滞的调节;同时,Miz1因子还可在TNFα诱导下被E3泛素连接酶Mule泛素化而降解,从而解除其对JNK信号通路的阻遏,致使JNK信号通路激活。对鼠源野生型Miz1因子(WT Miz1)的AKT磷酸化保守位点进行定点突变,得到磷酸化的突变因子S419AMiz1,并进行了免疫印记和细胞体内泛素化分析。结果显示:Miz1的磷酸化非但不是其泛素化所必需的因素,反而会对其泛素化起到一定的抑制作用。

Miz1 is an important transcription factor,and also a signal-and pathway-specific modulator or regulator.Upon TNFα stimulation,Miz1 undergoes ubiquitination and degradation,releasing its inhibition on JNK signaling pathway,which leads to the activation of JNK.Phosphorylation and ubiquitination have multiple connections.Recent study showes that protein kinase Akt can specifically phosphorylate Miz1 to regulate cell-cycle arrest after DNA damage.Through the site-directed mutagenesis of Mus wild-type Miz1 at specifically phosphorylation site to get S419A Miz1,and then immunoblotting and in vivo ubiquitination assay,the results show that phosphorylation of Miz1 by Akt is not requied for its ubiquitination,and even suppresses it