MRC Centre for Protein Engineering, Hills Road, Cambridge, CB20QH, UK.
Nucleic Acids Res. 2010 Jan;38(3):893-906. doi: 10.1093/nar/gkp1041. Epub 2009 Nov 20.
p53 maintains genome integrity by initiating the transcription of genes involved in cell-cycle arrest, senescence, apoptosis and DNA repair. The activity of p53 is regulated by both post-translational modifications and protein-protein interactions. p53 that has been phosphorylated at S366, S378 and T387 binds 14-3-3 proteins in vitro. Here, we show that these sites are potential 14-3-3 binding sites in vivo. Epsilon (epsilon) and gamma (gamma) isoforms required phosphorylation at either of these sites for efficient interaction with p53, while for sigma (sigma) and tau (tau) these sites are dispensable. Further, sigma and tau bound more weakly to p53 C-terminal phosphopeptides than did epsilon and gamma. However, the four isoforms bound tightly to di-phosphorylated p53 C-terminal peptides than did the mono-phosphorylated counterparts. Interestingly, all the isoforms studied transcriptionally activated wild-type p53. sigma and tau stabilized p53 levels in cells, while epsilon and gamma stimulated p53-DNA binding activity in vitro. Overall, the results suggest that structurally and functionally similar 14-3-3 isoforms may exert their regulatory potential on p53 through different mechanisms. We discuss the isoform-specific roles of 14-3-3 in p53 stabilization and activation of specific-DNA binding.
p53 通过启动涉及细胞周期停滞、衰老、细胞凋亡和 DNA 修复的基因的转录来维持基因组完整性。p53 的活性受翻译后修饰和蛋白质-蛋白质相互作用的调节。体外磷酸化的 p53 在 S366、S378 和 T387 位点与 14-3-3 蛋白结合。在这里，我们表明这些位点在体内是潜在的 14-3-3 结合位点。在体内，对于有效与 p53 相互作用，epsilon (epsilon) 和 gamma (gamma) 同工型需要在这些位点之一上磷酸化，而 sigma (sigma) 和 tau (tau) 同工型则不需要。此外，sigma 和 tau 与 p53 C 端磷酸肽的结合比 epsilon 和 gamma 弱。然而，与单磷酸化相比，这四种同工型更紧密地结合双磷酸化的 p53 C 端肽。有趣的是，所有研究的同工型都转录激活野生型 p53。sigma 和 tau 稳定细胞中的 p53 水平，而 epsilon 和 gamma 则在体外刺激 p53-DNA 结合活性。总的来说，结果表明结构和功能相似的 14-3-3 同工型可能通过不同的机制发挥其对 p53 的调节潜能。我们讨论了 14-3-3 在 p53 稳定和特定 DNA 结合激活中的同工型特异性作用。
