Distinct OGT-Binding Sites Promote HCF-1 Cleavage
Distinct OGT-Binding Sites Promote HCF-1 Cleavage
复制标题
DOI：
10.1371/journal.pone.0136636
复制
发表时间：
2015-08-25
期刊：
影响因子：
3.7
通讯作者：
Herr, Winship
中科院分区：
文献类型：
--
作者：
Bhuiyan, Tanja;Waridel, Patrice;Herr, Winship
人HCF-1（也称为HCFC-1）是一种转录辅助调节因子，其经历复杂的成熟过程，包括广泛的O-GlcNAc酰化和位点特异性蛋白水解。HCF-1蛋白水解产生两个活性的、非共价结合的HCF-1（N）和HCF-1（C）亚基，它们调节细胞分裂周期的不同阶段。HCF-1 O-GlcNAc酰化和位点特异性蛋白水解均由O-GlcNAc转移酶（OGT）催化，因此其显示出不寻常的双重酶活性。OGT在称为HCF-1（PRO）重复的六个高度保守的26个氨基酸重复序列处切割HCF-1。在这里，我们表征HCF-1的OGT裂解的底物要求。我们表明，HCF-1（PRO）重复切割信号具有特定的OGT结合特性。在切割位点处密切参与切割反应的谷氨酸残基特异性抑制与OGT及其结合辅因子UDP-GlcNAc的结合。此外，我们确定了一个新的OGT结合序列附近的第一HCF-1（PRO）重复切割信号，增强切割。这些结果表明，不同的OGT结合位点的HCF-1促进蛋白水解，并提供了新的见解，这种不寻常的蛋白酶活性的机制。
Human HCF-1 (also referred to as HCFC-1) is a transcriptional co-regulator that undergoes a complex maturation process involving extensive O-GlcNAcylation and site-specific proteolysis. HCF-1 proteolysis results in two active, noncovalently associated HCF-1(N) and HCF-1(C) subunits that regulate distinct phases of the cell-division cycle. HCF-1 O-GlcNAcylation and site-specific proteolysis are both catalyzed by O-GlcNAc transferase (OGT), which thus displays an unusual dual enzymatic activity. OGT cleaves HCF-1 at six highly conserved 26 amino acid repeat sequences called HCF-1(PRO) repeats. Here we characterize the substrate requirements for OGT cleavage of HCF-1. We show that the HCF-1(PRO)-repeat cleavage signal possesses particular OGT-binding properties. The glutamate residue at the cleavage site that is intimately involved in the cleavage reaction specifically inhibits association with OGT and its bound cofactor UDP-GlcNAc. Further, we identify a novel OGT-binding sequence nearby the first HCF-1(PRO)-repeat cleavage signal that enhances cleavage. These results demonstrate that distinct OGT-binding sites in HCF-1 promote proteolysis, and provide novel insights into the mechanism of this unusual protease activity.