主调控因子招募细胞周期蛋白C：细胞周期蛋白依赖性激酶8来磷酸化Notch胞内结构域，并协调激活与周转过程。

Mastermind recruits CycC:CDK8 to phosphorylate the Notch ICD and coordinate activation with turnover.

作者信息

Fryer Christy J, White J Brandon, Jones Katherine A

机构信息

Regulatory Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.

出版信息

Mol Cell. 2004 Nov 19;16(4):509-20. doi: 10.1016/j.molcel.2004.10.014.

DOI:10.1016/j.molcel.2004.10.014

PMID:15546612

Abstract

Notch signaling releases the Notch receptor intracellular domain (ICD), which complexes with CBF1 and Mastermind (MAM) to activate responsive genes. We previously reported that MAM interacts with CBP/p300 and promotes hyperphosphorylation and degradation of the Notch ICD in vivo. Here we show that CycC:CDK8 and CycT1:CDK9/P-TEFb are recruited with Notch and associated coactivators (MAM, SKIP) to the HES1 promoter in signaling cells. MAM interacts directly with CDK8 and can cause it to localize to subnuclear foci. Purified recombinant CycC:CDK8 phosphorylates the Notch ICD within the TAD and PEST domains, and expression of CycC:CDK8 strongly enhances Notch ICD hyperphosphorylation and PEST-dependent degradation by the Fbw7/Sel10 ubiquitin ligase in vivo. Point mutations affecting conserved Ser residues within the ICD PEST motif prevent hyperphosphorylation by CycC:CDK8 and stabilize the ICD in vivo. These findings suggest a role for MAM and CycC:CDK8 in the turnover of the Notch enhancer complex at target genes.

摘要

Notch信号通路释放Notch受体内结构域（ICD），其与CBF1和主调控因子（MAM）形成复合物以激活反应性基因。我们先前报道，MAM在体内与CBP/p300相互作用，并促进Notch ICD的过度磷酸化和降解。在此我们表明，CycC:CDK8和CycT1:CDK9/P-TEFb与Notch及相关共激活因子（MAM、SKIP）一起被募集到信号细胞中的HES1启动子处。MAM直接与CDK8相互作用，并可使其定位于核内亚结构域。纯化的重组CycC:CDK8在TAD和PEST结构域内使Notch ICD磷酸化，并且CycC:CDK8的表达在体内强烈增强Fbw7/Sel10泛素连接酶介导的Notch ICD过度磷酸化和PEST依赖性降解。影响ICD PEST基序内保守丝氨酸残基的点突变可阻止CycC:CDK8介导的过度磷酸化，并在体内使ICD稳定。这些发现提示MAM和CycC:CDK8在靶基因处Notch增强子复合物的周转中发挥作用。