Gfi1 ubiquitination and proteasomal degradation is inhibited by the ubiquitin ligase Triad1
Gfi1 ubiquitination and proteasomal degradation is inhibited by the ubiquitin ligase Triad1
复制标题
DOI：
10.1182/blood-2006-11-058602
复制
发表时间：
2007-11-01
期刊：
影响因子：
20.3
通讯作者：
Van der Reijden, Bert A.
中科院分区：
文献类型：
--
作者：
Marteijn, Jurgen A. F.;van der Meer, Laurens T.;Van der Reijden, Bert A.
生长因子独立1(Gfi1)是一种转录抑制因子，对许多不同的造血系统的功能和发育至关重要。Gfi1蛋白的表达受泛素-蛋白酶体系统的调节。在粒细胞中，Gfil1被蛋白酶体迅速降解，而在单核细胞中更稳定。Gfil1的泛素化和降解是如何调控的，目前尚不清楚。在这里，我们证明了泛素连接酶Triad1与Gfil1的DNA结合域相互作用。出乎意料的是，我们发现Triad1抑制了Will的泛素化，导致半衰期延长。SiRNAs下调内源性Triad1，导致Gfil1泛素化增加。在U937细胞中，Triad1导致内源性Gfi1蛋白水平增加，并以类似于Gfil1本身表达的方式减缓细胞增殖。缺少Gfi1结合域的Triad1突变体不影响Gfil1水平和增殖。由于抑制Gfil1泛素化既不需要蛋白酶体泛素也不需要Triad1泛素连接酶活性，这些数据表明Triad1与尚未鉴定的E3泛素连接酶竞争Gfil1结合，而E3泛素连接酶确实标记Gfil1蛋白酶体的降解。由Triad1调控的Gfil1蛋白水平的微调定义了该蛋白在造血中的意想不到的作用。
Growth factor independence 1 (Gfi1) is a transcriptional repressor essential for the function and development of many different hematopoietic lineages. The Gfi1 protein expression is regulated by the ubiquitin-proteasome system. In granulocytes, Gfil1 is rapidly degraded by the proteasome, while it is more stable in monocytes. How the ubiquitination and degradation of Gfil1 is regulated is unclear. Here, we show that the ubiquitin ligase Triad1 interacts with the DNA-binding domain of Gfil1. Unexpectedly, we found that Triad1 inhibited Will ubiquitination, resulting in a prolonged half-life. Down-regulation of endogenous Triad1 by siRNAs resulted in increased Gfil1 ubiquitination. In U937 cells, Triad1 caused an increase in endogenous Gfi1 protein levels and slowed cell proliferation in a similar manner when Gfil1 itself was expressed. A Triad1 mutant that lacks the Gfi1-binding domain did not affect Gfil1 levels and proliferation. Because neither proteasome-ubiquitin nor Triad1 ubiquitin ligase activity was required for the inhibition of Gfil1 ubiquitination, these data suggest that Triad1 competes for Gfil1 binding with as yet to be identified E3 ubiquitin ligases that do mark Gfil1 for proteasomal degradation. The fine-tuning of Gfil1 protein levels regulated by Triad1 defines an unexpected role for this protein in hematopoiesis.